# TrustFire EB03 2S-3P 18650 x 6 Battery Box



## Scott Novak (Mar 2, 2013)

I recently purchased a TrustFire EB03 2S-3P, 18650 x 6, Battery Box. 
I went on a 14 mile ride with plenty of potholes and the power was NOT interrupted a single time. It has contact springs on both the top and bottom of the Li-Ion cells. It appears that the power interruption issue has been resolved by the new design.

I've disassembled the battery box and I will be making a schematic of the protection circuit. But don't hold your breath. It may still have the problem of circuit damage if the Li-Ion cells are inserted incorrectly.

For now I'm posting photos of the box and it's circuit boards. I'll be adding a few more photos as time goes on. Stay tuned.

Scott Novak


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## Cat-man-do (May 16, 2004)

Good show. Looks like this box includes a protection circuit for the output voltage to the lamp. At least that is what the instructions on the box leads you to believe. My 4-cell box ( model EB02 ) has the same instructions on the box so perhaps mine has an output protection circuit as well. Very likely it does. Don't know why I didn't read everything written on the box before. I could of sworn it had indicated that it didn't use protection for the lamp circuit. :idea:

Question; Did yours come with the yellow battery indicators I see on your photos? Wish mine had those.


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## Velodonata (May 12, 2018)

Cat-man-do said:


> Question; Did yours come with the yellow battery indicators I see on your photos? Wish mine had those.


Those yellow stickers come with the case, the 4-cell versions have polarity indicators printed directly on the plastic in silver.


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## Scott Novak (Mar 2, 2013)

Yes, the yellow cell polarity stickers are attached to the inside of the 6-cell case.

I suspect that the same person that designed this previous case design also designed the EB03 box.








The circuit is nearly identical, INCLUDING the incompetent reverse protection circuit! What was changed in the protection circuit is that each series string of cells now has TWO power MOSFETs in parallel and has the addition of a 100KΩ resistor in series between Postive Li-Ion cell terminal and the MOSFET gates. The paralleled MOSFETS will likely slightly lower the voltage loss, but they don't cure the design fault of the protection circuit.

If all cells are installed correctly, the power MOSFETS turn on hard and have very low resistance and the battery pack will operate normally.

If you reverse 3 of the cells so that all of the exposed cell tops are of the same polarity, and the cell voltages are similar, no current will flow, there will be no output, and no damage will occur.

If you reverse the polarity of ALL of the cells, the power MOSFETs will NOT conduct, there will be no current flow through the cells, there will be no output, and no damage to the circuit or to the cells, and the reverse cell protection circuit will work as intended,

The problem occurs if you reverse the polarity of any one pair of series connected cells. It puts the cells in a series connected loop and massive current will flow for a fraction of a second until the tops of the power MOSFETS are blown off! The power MOSFETs blowing up are acting like fuses and are the only thing that will prevent the Li-Ion cells from venting and/or catching on fire.

Even if you reinstall the cells correctly, you have no output from the battery pack and you will be riding in the dark.

The 8.4V circuit has overcurrent protection, overvoltage protection, and undervoltage protection.

HOWEVER, like previous versions, the series connection between the Li-Ion cells is NOT sensed and the protection circuit only sees the average voltage of two Li-Ion cells in series, so voltage imbalances can occur while charging cells inside the case.

I suspect that the USB DC/DC convertor is also current limited. I haven't finished making the schematic diagram, but there also appears to be an additional bipolar transistor and a power MOSFET in the circuit.

The voltage indicator appears to be the same as previous designs.

When you strap the case onto a stem or a bicycle frame member it does slide around. It might be beneficial to glue a grippy pad to the side of the box.

All in all, this battery box appears to have the least amount of problems of any available battery 18650 box, at least for 4 or 6 cell versions. It doesn't appear to have the problem of power disconnection caused by road bumps. Isn't that ironic that you need to be very careful to install the cells with the correct polarity or you will damage the protection circuitry?

Scott Novak


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## Scott Novak (Mar 2, 2013)

Here are the protection circuits for the Trustfire EB03 2S-3P 18650 x 6 Li-Ion Battery Box.









Click on the schematic to view it larger.

The voltage losses consist of the resistance of 4 battery contact springs, and resistance of 3 Power MOSFETs in series with the Li-Ion cells.

Note that the power MOSFETs intended for reverse polarity protection are paralleled to reduce voltage loss.

Also, U2 and U3 are dual power MOSFET packages and they are also paralleled for lower voltage losses.

I haven't measured the voltage losses yet.

The reverse polarity circuit may require a second MOSFET in series to work correctly.

Note: Schematic edited because of an error.

Scott Novak


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## -Archie- (Aug 25, 2013)

Many thanks for schematic! :thumbsup:

I've ordered 4-cell version of that box; probably the circuit is identical except one 2s part.


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## Scott Novak (Mar 2, 2013)

Trustfire EB03 2S-3P 18650 x 6 Battery Box
LED Battery Voltage/Charge Indicator Circuit.









Click Schematic for Larger View

Note the circuit board layout error. They connected C4 to the wrong part of the circuit. C4 should be connected from the enable input to ground (across the switch contacts) to reduce general noise problems and eliminate switch contact bounce noise problems specifically.

Scott Novak


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## ledoman (Apr 17, 2012)

Scott, great job! Looks like some student has designed those things for his homework. Took things from somewhere and put (copy/paste) together. Then tried: does it works, yes, then let's do it on massive scale. No checking what is actually happening.
Now only USB charging part of circuit is missing.


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## Scott Novak (Mar 2, 2013)

EB03 2S-3P 18650 x 6 USB Converter Circuit









Click Schematic for Larger View.

Note the addition of a MOSFET switch to power up and down the converter circuit. It should reduce the idle current drain on the Li-Ion cells.

Also note that both the USB converter circuit and the LED battery charge/voltage indicator circuit draw their power from the Li-Ion cells BEFORE the battery protection circuits. It may be possible to drain the Li-Ion cells to the point of permanent damage.

As I really don't have much use for USB power I'll probably disable the USB converter.

Note: The schematic layout has been edited for greater clarity. No actual circuit changes have been made.

Scott Novak


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## Scott Novak (Mar 2, 2013)

ledoman said:


> Looks like some student has designed those things for his homework. Took things from somewhere and put (copy/paste) together. Then tried: does it works, yes, then let's do it on massive scale. No checking what is actually happening.


That's it in a nutshell. The reverse voltage protection circuit (Right out of an application note) will only work with ONE series string of cells, not two stings of cells or 3 strings of cells.

Nobody bothered to test the operation, or even checked to see that the PCB layout was correct.

The circuit board layout is also poor. The freewheeling diode currents are flowing through the ground of the convertor IC introducing noise and otherwise reducing the stability of the converter. I can't say that the decoupling of the power supply is much better.

It's a far cry from the testing that a reputable US manufacturer does. I'd spend 3 weeks just performing the safety testing on a product, and that's not counting the hundreds of hours spent testing the actual performance of the product to make sure that it's meeting all specifications.

What is so frustrating is that there aren't even any better battery box options available at any price.

Scott Novak


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## ledoman (Apr 17, 2012)

Can you show on the PCB picture where to cut traces to do that. It would be good for someone who would like to do the same. How much will reduce parasitic drain when cutting off USB output?


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## Scott Novak (Mar 2, 2013)

Unless the USB converter is turned on, there will be virtually no parasitic drain caused by the converter, as it is switched out of the circuit by the power MOSFET Q1.

At full charge there is 42µA of current flowing through the voltage divider R2 & R3 of the battery protection circuit. I don't have any specs on the operating current of the 7022 IC or the voltage indicator IC.

I don't want to have an extra USB jack dangling on my bike as I'm not using it anyway. I will probably use my previous battery box, without the battery spring contacts on the bottom, for USB power if I ever need, it, but not for use while mounted on my bike.

The easiest way to disable the USB converter is to unsolder the Source of the MOSFET Q1 (which supplies power to the converter.) and lift it up off of the circuit board.

Scott Novak


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## Scott Novak (Mar 2, 2013)

BTW, does anyone have any idea which IC is being used for the LED voltage/charge indicator? I can't see any markings on it.

Scott Novak


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## garrybunk (Feb 12, 2014)

Nice work Scott! 

-Garry


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## Cat-man-do (May 16, 2004)

First, just want to say...Great work Scott! Nice to have someone on here that knows something about electronics. Now for the big question; Any idea yet on how much output current the protection circuit is going to allow to the lamp output? If you're using a six cell box I'd like to think these might become useful once they're hooked up to a lamp that requires a good bit of juice.

I've yet to test my 4 cell box on a ride. Was going to do it today but accidentally stepped on my glasses when I woke up today. That meant I had to rush on down to the local _Lens Crafters_ to have them fixed and then try to do another errand that had to be done. By the time I was done running around I was so tired I fell asleep on the couch ( again ) and didn't get up till about 9:30pm.  Really wishing now that I hadn't agreed to work for one of my co-workers on Saturday...:nonod:

( edit...Man...I am so tempted to play hooky from work tomorrow....:devil: )


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## Scott Novak (Mar 2, 2013)

Cat-man-do said:


> Any idea yet on how much output current the protection circuit is going to allow to the lamp output?


Unfortunately, only 2.0Amp output current maximum. The reason for this is that there is only one protection circuit. It must protect against over current under the worst case conditions.

Many 18650 Li-Ion cells have a maximum 2.0A discharge current specification. The worst case condition is when only two Li-Ion cells are installed in the box. The protection circuit MUST limit at 2.0A maximum.

Installing additional cells only allows longer for runtime, but NO increase in output current limit. Additional cells also reduce the average internal resistance which allows longer runtime in subfreezing conditions. But you are using the same current limit circuit for all cells in parallel, so you are stuck with a maximum of 2.0A current draw.

For higher than 2.0A output current, each series string of Li-Ions cells should have it's own protection circuit limiting the output to 2.0 A maximum. The total current from each parallel string of Li-Ion cells would add up. 4-cells in the box could safely output 4.0A and 6-cells could output 6.0A maximum and still be safe.

If I remember correctly, the output power connector is only rated for a maximum of 6A. Someone please correct me if I'm wrong.

There isn't enough room for 3 protection circuits on the PWB. There would be if the USB Converter circuit was eliminated.

If you really needed a USB output, it would make more sense to have a separate USB converter that would operate from 8.4VDC and plug it into the battery pack when you need it.

Scott Novak


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## Scott Novak (Mar 2, 2013)

It should also be noted that, like most previous Chinese battery boxes, the cells are NOT monitored individually. Charging inside the battery box might not result in evenly charged cells. As such, each series pair of cells should be closely matched so that they charge evenly.

If you look at the protection circuit schematic, R2 and R3 are connected in series across the series Li-Ion cells to simulate the junction of the series cells that connects to the sense terminal of the 7022 protection IC. At least they used 1% tolerance resistors.

Some of you might be tempted to wire the junctions of all three series Li-Ion cell strings together and connect the junctions directly to the protection IC, so that all cells will be charged to equal voltages. But unless you plan to incorporate reverse polarity protection for EACH individual cell, don't do it! Reversing the polarity of just one cell will result in huge current flowing though the cell which can cause it to vent, or explode, or catch on fire.

This modification is also of very little benefit when you are charging the cells inside the battery box. Because there is only ONE protection circuit, you are limited to a charging current of only 2.0 Amp. With only 2.0 A of charging current available, if you are using high capacity 3,500 mAH Li-Ion cells, you can only charge those cells at a maximum rate of .2C (C = the cell capacity rating.) and it will take forever and a day to charge them.

For longest cell life the general wisdom is to use a charge rate of a maximum of .8C. This means that in an external battery charger you could be charging the cells with four times the current and four times faster than you could inside the battery box!

So unless you are willing to make a new circuit board with 3 individual protection circuits, add 3 separate contacts to connect the junction of each series pair of cells individually to it's respective protection circuit, just use the battery box as is with matched Li-Ion cells.

This battery box not perfect but it's now usable, provided that you are careful to install the cells with the correct polarity. It would be best to remove the cells and charge them inside an external battery charger. If you have an 2.0 Amp 8.4 VDC charger that you can connect to the battery box, expect it to take overnight and then some to charge.

Scott Novak


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## Cat-man-do (May 16, 2004)

Scott Novak said:


> *Unfortunately, only 2.0Amp output current maximum.* The reason for this is that there is only one protection circuit. It must protect against over current under the worst case conditions.
> 
> Many 18650 Li-Ion cells have a maximum 2.0A discharge current specification. The worst case condition is when only two Li-Ion cells are installed in the box. The protection circuit MUST limit at 2.0A maximum.
> 
> ...


Okay, now I'm scratching my head... I did test the box's main lamp output when I first got it using my ITUO XP3 which I'm pretty sure ( with three XML2's ) must be drawing more than 2A ( *although I could be wrong about that if the LED's are connected in series ). Didn't notice any dimming or lack of output when I first hooked it up. Now I'm going to have to confirm that by measurement. That means I have to find the wire's and clips I use for amp battery testing which I haven't used in quite some time.

The box that the battery holder came in does state that the output is suppose to be 2100ma which ( in how it was worded ) I took to mean that the USB circuit was limited to 2.1A and that it was on a separate loop from the main lamp output. All I can say at this point is that I hope you are wrong.


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## Scott Novak (Mar 2, 2013)

8.4VDC @ 2,000 mA is the specification. The accuracy of that specification is up for speculation and ought to be measured.

The current limit is determined by the voltage drop across the power MOSFETs inside U2 & U3. That voltage drop also changes with the MOSFET temperature because the Rds On changes resistance with temperature. So the designer needs to be careful with power MOSFET selection to achieve the necessary voltage drop to obtain the desired current limit.

It's possible that there may be different versions of the protection circuit available that use a different voltage to trip the current limit that will allow the use of power MOSFETs with a lower Rds On.

It's also possible that when using both the 8.4V output AND the USB output you may exceed the recommended maximum discharge current of some Li-Ion cells. This is just more reason to disable the USB DC/DC converter circuit.

After I test to see whether or not the USB DC/DC converter circuit can draw the Li-Ion cell voltage to an unsafe level, I am going to disable the USB circuit in my battery box. I may keep the voltage indicator intact.

Scott Novak


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## Scott Novak (Mar 2, 2013)

I finally got around to reassembling the battery box after someone stole the Li-Ion battery pack off of my bicycle. Not great loss as it was made from Li-Ion cells from a dead computer battery pack. But it still left me without light and that pissed me off.

Anyway, I put two 18650 Li-Ion cells into the battery box, hooked it up to my bike light and let it discharge until the Li-Ion protection circuit disconnected power to the light. However, as the schematics show, the USB supply will still continue to draw power from the Li-Ion cells after power to the lights is shut off.

I connected my cell phone's USB port to the battery pack and it charged my cell phone for a short time. Then it stopped charging my phone. An LED on the battery box was blinking and I just let it continue. I finally pulled the Li-Ion cells and measured one at 3.21 VDC and the other at 2.06 VDC. That's an average of 2.635VDC per cell. The LED was still flashing when I pulled the cells and would have continued to discharge the cells.

Anyone feel safe with a battery box drawing voltage down to 2.635VDC per cell?

I will probably buy a second battery box for a backup. But I'll need to be extra cautious while inserting the Li-Ion cells as a polarity reversal will cause the protection FETs to explode. Eventually I'll get around to disconnecting the voltage indicator circuit as well as the USB supply.

Scott A. Novak


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## arc (Sep 9, 2004)

Is it possible to get the battery connector pcb's in the bottom of the box out?

Then you could cut the traces and solder some five amp 1206 fuses or zero ohm resistors over the cuts making it a lot safer.

Its likely they are counting on the shitty steel springs to fail and loose contact before the fet's or batteries explode.


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## ledoman (Apr 17, 2012)

Scott Novak said:


> Anyone feel safe with a battery box drawing voltage down to 2.635VDC per cell?


Well, there are some cells declared to be discharged down to 2.5V, so yes. But on the other hand, cell voltage raises just after disconnecting so you have measured raised voltage. In reality it might be discharged just down to 2V. You would need to measure voltage in case when used to know exact values.

Anyway it's not good to use pack down to that point except in emergency.


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## Scott Novak (Mar 2, 2013)

ledoman said:


> But on the other hand, cell voltage raises just after disconnecting so you have measured raised voltage.
> 
> The LED and the resistors always across the cells is a very light load which would not cause much internal voltage loss. So the out of circuit voltages that I measured are valid.
> 
> ...


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## C-man23 (Mar 8, 2012)

Thank you for the info! Do you have any recommendations on what batteries to use for this pack? Lots of cheap options on eBay, but is one better than the others?


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## RAKC Ind (Jan 27, 2017)

ya dont use cheap batteries.

Dont buy them off Ebay either.

Buy proper branded cells that are protected from reputable places. They dont have to be expensive but if they arent a known brand name chances are they are either garbage or dangerous or both.

Sent from my SM-G950U using Tapatalk


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## C-man23 (Mar 8, 2012)

I really appreciate the help, RAKC. Would flat top batteries like the ones linked below work in the Trustfire case? The Google Machine said these are supposed to be the top 18650 batteries. https://www.batteryjunction.com/sam...MIh5Wf6pa73gIVkLbACh2x-wctEAQYASABEgKrj_D_BwE


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## Scott Novak (Mar 2, 2013)

C-man23 said:


> Would flat top batteries like the ones linked below work in the Trustfire case?


C-man,

That style Li-Ion cell will work in the Trustfire battery case. 6 of those cells in a 2S-3P configuration are capable of 45,000 mA output. However, the protection circuit in the case will only allow a maximum of 2,000 mA output to your lights through the 8.4 V connector.

In warm weather the high current output of those cells is unnecessary and you would have longer runtime with lower current output cells with a higher capacity rating.

HOWEVER, in cold weather the run time can be reduced from hours to just minutes because the internal resistance of a Li-Ion cell increases dramatically as the cell temperature decreases. That is when high current output Li-Ion cells with low internal resistance are better. Even when their internal resistance increases as the cell becomes colder, the internal resistance will be lower than higher capacity lower current cells, and the runtime of high current output cells will be longer.

If you are in sunny southern California a lower current output cell with a higher capacity rating would be better.

But if you ride in cold winter weather like I do in Minnesota, you would be better off with high output current cells, like the ones in the ad you linked. And in summer switch to lower current cells with a higher capacity rating.

Also, don't leave Li-Ion cells on your bicycle parked in the cold. Bring the batteries inside with you to keep them warmer.

I plan to make an insulated case made from closed cell foam to put my battery pack into to keep it warmer while I ride in the cold.

As for myself, I'm using Li-Ion cells reclaimed from bad computer battery packs as they don't cost me anything.

Scott A. Novak


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## garrybunk (Feb 12, 2014)

Those Samsung 30Q's are one of the best cells balancing high capacity with high output capability. I bought (4) 30Q button tops from Banggood for my BLF Q8. Those cells are pushing upwards of 20amps in that monster. 

-Garry


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## Tracebeau (Nov 5, 2018)

Scott Novak said:


> 8.4VDC @ 2,000 mA is the specification. The accuracy of that specification is up for speculation and ought to be measured.
> Scott Novak


So what would happen if one were to plug in a light that draws over 2 amps? I have a light that draws approx. 3.7 amps on high that I would like to use with a pack like this.


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## ledoman (Apr 17, 2012)

It will cut off the power. I would replace the whole electronics with 5A like this https://www.ebay.com/itm/2S-5A-BMS-...cks-18650-Li-ion-lithium-Battery/282779274488
Or even 8A like tghis https://www.ebay.com/itm/2S-7-4V-8A...ger-BMS-PCM-Protection-PCB-Board/362430707530


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## Scott Novak (Mar 2, 2013)

Tracebeau said:


> So what would happen if one were to plug in a light that draws over 2 amps? I have a light that draws approx. 3.7 amps on high that I would like to use with a pack like this.


There are 18650 Li-Ion cells are aren't rated for more than 2.0 A output. You DON'T want a single protection circuit that allows more than 2.0 A output. A protection circuit that allowed more than 2.0 A output could damage the cells if only one pair of cells was used. This is a safety issue when ANY style Li-Ion cell can be used in the box.

A better solution is to use a separate 2.0 A protection circuit for EACH series string of Li-Ion cells. That would allow a total of 6.0 Amps output if all 6 cells were installed.

It would also make it easier to add a separate reverse polarity protection circuit for each series string of cells.

Also keep in mind that the 8.4 V power connector that they are using is only rated for 6.0 Amps maximum, if I remember correctly.

Scott A. Novak


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## ledoman (Apr 17, 2012)

Why use shitty 2A cells when you have good brand ones that can easily stand 10A (NCR18650GA for example) or more? Most brand cells can stand 4-5A, at least.


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## Scott Novak (Mar 2, 2013)

ledoman said:


> Why use shitty 2A cells when you have good brand ones that can easily stand 10A (NCR18650GA for example) or more? Most brand cells can stand 4-5A, at least.


Ledoman,

It's a safety issue, as you have no idea what kind of cells someone will insert into the box.

You would NEVER get any kind of safety certification if you allowed more than 2.0 Amps output from each series string of cells.

I haven't checked lately but in the past, cells with a 2.0 A output current rating had the highest capacity rating and for anyone riding in not freezing weather would be a better choice. Also, not many lights are requiring more than 2 Amps of current.

But as I already mentioned, you can still SAFELY get 6.0 Amps out of the box if you use a separate 2.0 A protection circuit for each series string of cells. This would also allow charging at a 6.0 amp rate while the cells are still in the box.

Scott Novak


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## gr8fasushi (Aug 14, 2014)

I picked up a couple of these boxes, but after reading through this thread, it's confusing as to what the consensus is, especially since I don't have any background with this subject. I looked up the best safe battery I could find to match with these boxes. Would these be a good choice: Orbtronic 3500 maH batteries from orbtronic.com:

https://www.orbtronic.com/18650-protected-battery-3500mah-lithium-ion


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## garrybunk (Feb 12, 2014)

gr8fasushi said:


> I picked up a couple of these boxes, but after reading through this thread, it's confusing as to what the consensus is, especially since I don't have any background with this subject. I looked up the best safe battery I could find to match with these boxes. Would these be a good choice: Orbtronic 3500 maH batteries from orbtronic.com:
> 
> https://www.orbtronic.com/18650-protected-battery-3500mah-lithium-ion


You're paying a premium for the Orbtronic name (nothing wrong with that, just noting it). In the US you can use Mountain Electronics as another source for quality cells with high quality protection circuits. Mountain has the same cell also with a Seiko protection circuit for $9.95ea. You also don't need "high-drain" cells in this case, since you'll be limited to about 2A output anyway. You could drop back to the Samsung 35E's.

EDIT - Well, as stated above, I guess the high-drain cells would help deal with use in the cold weather better, and to be honest the price difference isn't that much.

Are there issues with the length of this cell in this case? (I don't know, but that's something to check into.)

-Garry


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## gr8fasushi (Aug 14, 2014)

garrybunk said:


> You're paying a premium for the Orbtronic name (nothing wrong with that, just noting it). In the US you can use Mountain Electronics as another source for quality cells with high quality protection circuits. Mountain has the same cell also with a Seiko protection circuit for $9.95ea. You also don't need "high-drain" cells in this case, since you'll be limited to about 2A output anyway. You could drop back to the Samsung 35E's.
> 
> EDIT - Well, as stated above, I guess the high-drain cells would help deal with use in the cold weather better, and to be honest the price difference isn't that much.
> 
> ...


thanks for the input and the suggestions. Safety is definitely a priority. from what it looks like with the springs, it should fit? Speculating at this point but I'll find out soon enough.

And from what I gather, I should pull these cells out to charge instead of charging them in the case.


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## Scott Novak (Mar 2, 2013)

gr8fasushi said:


> I picked up a couple of these boxes, but after reading through this thread, it's confusing as to what the consensus is, especially since I don't have any background with this subject. I looked up the best safe battery I could find to match with these boxes. Would these be a good choice: Orbtronic 3500 maH batteries from orbtronic.com:
> 
> https://www.orbtronic.com/18650-protected-battery-3500mah-lithium-ion


That's a protected cell and it will have slightly higher voltage losses than an unprotected cell and it is much more expensive with NO benefits when used in a battery box.

Looking around, it appears that the highest capacity commonly available 18650 cells being made today are typically around 3,500mAH with around a 10A output rating. The battery box will not allow more than 2.0A output current.

If you only installed two cells in the battery box, the most current that the box would allow to be drawn from the cells is 2.0A.

If you have 6 cells installed, the maximum current draw from any cell would be 0.66A. At temperatures of 40°F and above there is NO advantage to using a higher current capacity cell.

But at very low temperature, using a lower capacity L-Ion cell with a 30A output current rating and 1,500mAH may provide a longer run time than a 10A 3,500 mAH cell. The reason being is that the internal resistance of the higher current cell is lower than low current cells, so there will be less internal voltage loss. At subzero temperatures, internal resistance increases dramatically.

Also, while you might easily get by only using 2 cells in the battery box in the summer, in winter you will likely need to use 6 cells to get the internal resistance low enough to keep the voltage loss to a reasonable level

If you only ride in warm weather, then choose a higher capacity unprotected cell such as 3,500 mAH 10A cell. If you are riding in subzero weather you will probably want to use a 1,500 mAH 30A cell.

I'll test the box with a protected cell to see if it fits after I vote.

Scott A. Novak


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## gr8fasushi (Aug 14, 2014)

Scott Novak said:


> That's a protected cell and it will have slightly higher voltage losses than an unprotected cell and it is much more expensive with NO benefits when used in a battery box.
> 
> Looking around, it appears that the highest capacity commonly available 18650 cells being made today are typically around 3,500mAH with around a 10A output rating. The battery box will not allow more than 2.0A output current.
> 
> ...


thank you for the in depth explanation. I look forward to your results!


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## garrybunk (Feb 12, 2014)

Well, if you use protected cells (and they fit), it's some extra safety against shorts or unbalanced cells used together causing any issues. Also much safer handling them out of the box. I say it's a good call to go protected. You're not going to see that much performance difference between protected & unprotected cells in this case or in general with the level of current draw on most of our lights. 

-Garry


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## garrybunk (Feb 12, 2014)

Oh, and yes, preferred to charge them out of the box in a quality charger (like an Xtar).

-Garry


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## Scott Novak (Mar 2, 2013)

I just installed a protected cell into the battery case and the cover seats completely into the case.

If you have protected 18650 cells laying around there is no reason that you can't use them.

Scott A. Novak


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## Ottoreni (Jan 27, 2004)

Been following this thread since it started. Last night my Magicshine battery lost juice after 45 minutes and the MJ 880 light went off. Last year it was able to light for just over 2 hours.

My question, is this battery box good for a novice? I have used 18650 batteries on a handheld flashlight for years, and I have a XTAR charger. I like the idea of when the 18650 batteries go bad, just getting new ones. 

The one thing I pick up from this thread is to be careful placing the batteries in the box the right way. Other than that, I just don't see too many negatives ( I mostly ride in warm weather).

Any thoughts? Also, did you order direct from Trustfire or a third party vendor?

Thanks much!


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## C-man23 (Mar 8, 2012)

I bought the battery box this past week and it looks really nicely built. To me, the battery orientation is super easy. They list the + on the inside of the box so you know which way to put in the batteries, and the lid will only go on the correct way. I was planning on testing it out tonight, but woke up to snow on the ground, so it will be delayed.

I ordered it from Amazon (link in previous post) and received it in 2 days with prime.
I plan on buying another and running both of these lights off of these packs. I will have a lower grade battery box as a backup in case I run out of juice on the trails.


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## Ottoreni (Jan 27, 2004)

Thanks for the info. I will order it from Amazon, too. Do not want to order it from China and wait 2 - 3 weeks for it.

Also planning on getting some unprotected cells as the box has built in protection and I plan to charge the batteries in my XTAR charger.


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## gr8fasushi (Aug 14, 2014)

I have a really dumb question. it says the max for 8.4V input is 2000 maH. Does that mean the maximum it can charge through 8.4V port is 2000maH? or is that overall capacity of the case? for instance, if I put in 4 x 3500 maH cells, would I theoretically get 14000 maH through this case?


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## Scott Novak (Mar 2, 2013)

gr8fasushi said:


> I have a really dumb question. it says the max for 8.4V input is 2000 maH. Does that mean the maximum it can charge through 8.4V port is 2000maH? or is that overall capacity of the case? for instance, if I put in 4 x 3500 maH cells, would I theoretically get 14000 maH through this case?


With 6 - 3,500 mAH cells in the case in it's 2S3P configuration, it would have a 10,500 mAH capacity. You have to remember that cells in series do NOT increase the mAH rating. Only connecting cells, or series strings of cells, in parallel will increase the mAH rating.

The protection circuit will only allow a maximum amount of 2,000 mA to pass through the 8.4 V power connector, no matter how many cells you have in the box or what their combined current rating or rated mAH capacity is.

So with 6 - 3,500 mAH cells in the 2S3P configuration inside the box. it would output 2,000 mA of current for 5.25 hours, 1,000 mA of current for 10.5 hours, and 500 mA of current for 21 hours, and so on.

Scott A. Novak


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## gr8fasushi (Aug 14, 2014)

thank you for the explanation! I have a pair of BT40s with a chinese 6 cell battery pack rated at 10200 maH, and I compared it side by side with the EB02 battery box (the 4 cell version). the chinese battery last 3 hours on High while the EB02 with the orbtronic 3500 maH cells ran past 6 hours and 30 minutes before I had to leave the house and turn it off. Needless to say I'm pleasantly surprised how long it lasted.


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## DrvLikHell (Aug 9, 2016)

Just a heads up for people following this thread and this box, Amazon has it for $10.87 right now, with 2 day Prime shipping. That's even cheaper than getting it from China through eBay, Aliexpress, etc. Not to mention several weeks faster.

http://a.co/d/91ldXyG


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## ledoman (Apr 17, 2012)

Depends where on the globe you live  Not for me. :/


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## Scott Novak (Mar 2, 2013)

Do check out the Amazon ad:
https://www.amazon.com/dp/B07CV44ZDQ/ref=cm_sw_r_cp_ep_dp_qC-9BbNFKK8JZ

Scroll down to the example photo of the box "strapped" to the top tube. Note that the straps do NOT go through the strap retaining slots in the box and at the first bump the box would fall out of the strap. SMH.

Scott A. Novak


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## -Archie- (Aug 25, 2013)

Making good ad pictures does not require understanding of how to use pictured device properly:
https://ic.pics.livejournal.com/viatcheslav/15374888/716742/716742_original.jpg


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## DrvLikHell (Aug 9, 2016)

Am I missing something regarding the indicator light on the box? I received my box yesterday and when I push the button, the USB power turns on and only one indicator light comes on even though all the batteries are fully charged. Isn't it supposed to display how much charge is left in the batteries? As in three lights for full charge, two for half charge, and one for "you'd better head home"?


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## Scott Novak (Mar 2, 2013)

DrvLikHell;Isn't it supposed to display how much charge is left in the batteries? As in three lights for full charge said:


> With fully charged cells mine only shows one green light.
> 
> I never use the indicator, as it enables the 5V USB output and drains the cells faster. But I think the LEDs are different colors and it just turns on a different color as the voltage drops.
> 
> Scott A. Novak


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## isleblue65 (Sep 5, 2009)

-Archie- said:


> Making good ad pictures does not require understanding of how to use pictured device properly:
> https://ic.pics.livejournal.com/viatcheslav/15374888/716742/716742_original.jpg


Say it isn't so. 










Sent from my iPhone using Tapatalk


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## abrooks (Feb 1, 2015)

I'm just going to add my name to the list on this thread. 

I was contemplating one of these. I have run a 2s2p pack for the last 4 years (with some mods) and it has served me very well. I use it with laptop batteries. I have quite a large stash of them as we have recently been upgraded at work.

I would run two lights on my bars off one of these. My eye sight is not what it used to be, as a varifocal wearer I need all the help I can get.


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## Tracebeau (Nov 5, 2018)

Just an FYI, but this box is capable of outputting more than 2000ma (2A) of current. Here's my bl70s light drawing over 3 amps from the box with no problems. This was done with 4 old Samsung ICR18650-26f cells. I hope this helps.


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## reinera (Dec 5, 2018)

Hello, 
one question to the PowerButton. When the button is pressed, it will activate the 5V USB output, right? 

Will the USB output be deactivated with a second push? Or will the USB output be deactivated when no load is connected after a certain time?

I have a USB light with a switch, and it is anoying to use it with a normal powerbank which is disabled shortly after light is switched off. 

Best regards Reiner

And great job Scott!


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## agnostic (Dec 8, 2018)

Tracebeau said:


> Just an FYI, but this box is capable of outputting more than 2000ma (2A) of current. Here's my bl70s light drawing over 3 amps from the box with no problems. This was done with 4 old Samsung ICR18650-26f cells. I hope this helps.


I want to buy this light and consider buying TrustFire EB03 box.

Could you tell me how long your batteries last? I need at least 6 hours on medium, which draws about 1,4A.

I plan to buy 6 NCR18650B, so in theory I get 10200mah, which should give me more than 7 hours, but from what I've read here this box may have some issues that will cause it not to last that long. Also, it's getting pretty cold so I need to take that into consideration too.

Maybe KBP-18650B2S3P or even KBP-18650B2S4P will be a better idea? Or maybe just buying more NCR18650B and replacing them? This is probably a cheaper option, but is it better in terms of how long it will last with this light?

Btw, are those rubber straps taken from another battery pack? Or can they be bought separately? They seem really convenient and secure.


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## Cat-man-do (May 16, 2004)

agnostic said:


> ...Could you tell me how long your batteries last? I need at least 6 hours on medium, which draws about 1,4A.
> 
> I plan to buy 6 NCR18650B, so in theory I get 10200mah, which should give me more than 7 hours, but from what I've read here this box may have some issues that will cause it not to last that long. Also, it's getting pretty cold so I need to take that into consideration too.
> 
> ...


How long any one's lamp will last with a battery pack ( or cell holder ) is really a hard call, even if you know the current draw. I'm pretty sure I could get six hours on a good 4-cell if all I ever used was medium levels but that really depends on what you call medium level and what type of lamp you are using.

The advantage of using one of the Trustfire cell holders ( either 4 or 6 cell ) is that you can carry as many loose cells along as you think might be necessary. I have one of the 4 cell holders. If I were planning a 6 hour ride I'd likely carry two extra cells. That way if my cell holder cut out after 4 hours all I have to do is take out the 4 cells and put the two back-ups in. Since the holder only needs two cells in series to work the holder also will work with just two cells. That's good enough for two hour run time as long as I'm not running max output more than a couple minutes here or there. The biggest disadvantage to using a cell holder is that there are going to be some minute voltage drops across the cell contacts. This might shorten the run time ten minutes or so ( depending on cell type and weather factors ) but having the advantage of being able to carry and use more cells more than enough outweighs that minor negative in my opinion.


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## agnostic (Dec 8, 2018)

Cat-man-do said:


> The advantage of using one of the Trustfire cell holders ( either 4 or 6 cell ) is that you can carry as many loose cells along as you think might be necessary. I have one of the 4 cell holders. If I were planning a 6 hour ride I'd likely carry two extra cells. That way if my cell holder cut out after 4 hours all I have to do is take out the 4 cells and put the two back-ups in. Since the holder only needs two cells in series to work the holder also will work with just two cells. That's good enough for two hour run time as long as I'm not running max output more than a couple minutes here or there. The biggest disadvantage to using a cell holder is that there are going to be some minute voltage drops across the cell contacts. This might shorten the run time ten minutes or so ( depending on cell type and weather factors ) but having the advantage of being able to carry and use more cells more than enough outweighs that minor negative in my opinion.


If the difference between run times is only ten minutes or so, then it's definitely worth it. Thank you for the clarification, I'll order the cell holder and buy 8 cells just to be safe.

Now I have to figure out why the cells are so expensive in China. Even in Poland I can buy them cheaper, which is really weird. Except for Liitokala fakes, they are dirty cheap, but I'd rather buy something that many people recommend.


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## Scott Novak (Mar 2, 2013)

Tracebeau said:


> Just an FYI, but this box is capable of outputting more than 2000ma (2A) of current. Here's my bl70s light drawing over 3 amps from the box with no problems. This was done with 4 old Samsung ICR18650-26f cells. I hope this helps.


The over-current limit of the TrustFire EB03 is specified as 2,000 mA.

However, the over-current limit is determined by the On resistance of power MOSFETs U2 and U3. If they didn't select the power MOSFETs correctly, the over-current limit will not be as specified.

Surprise, Surprise, Surprise! (Said in Gomer Pyle fashion.) Another Chinese product that doesn't meet it's own specifications.

Scott A. Novak


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## Scott Novak (Mar 2, 2013)

reinera said:


> When the button is pressed, it will activate the 5V USB output, right?
> 
> Will the USB output be deactivated with a second push? Or will the USB output be deactivated when no load is connected after a certain time?


When you press the button, a voltage indicator LED will light up and also turn on the 5V USB power circuit.

A voltage indicator LED will continue to be lit and the 5V USB circuit will continue to output power until you press the button again, which causes the voltage indicator LED to turn off which then causes the 5V USB circuit to turn off.

Basically, whenever a voltage indicator LED is turned on the 5V USB circuit will also be turned on.

Scott A. Novak


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## arc (Sep 9, 2004)

Scott Novak said:


> The over-current limit of the TrustFire EB03 is specified as 2,000 mA.
> 
> However, the over-current limit is determined by the On resistance of power MOSFETs U2 and U3. If they didn't select the power MOSFETs correctly, the over-current limit will not be as specified.
> 
> ...


What are the chances of the output changing with temperature? It appears none of the protection circuits can be trusted.

I'm starting to think stripping the components off of the board, ditch the usb, jumper things for direct output and use protected cells is the way to go.


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## Scott Novak (Mar 2, 2013)

arc said:


> What are the chances of the output changing with temperature? It appears none of the protection circuits can be trusted.


Most of the internal Li-Ion cell protection circuits work about the same as the external TrustFire EB03 protection circuit and are dependent upon the on resistance of the power MOSFETS to determine the maximum output current. As the temperature increases, so does the on resistance of the power MOSFETs. As a result, when the temperature increases, the protection circuit will turn off at a lower maximum current for either an internal or external protection circuit.



arc said:


> I'm starting to think stripping the components off of the board, ditch the usb, jumper things for direct output and use protected cells is the way to go.


The protected cells themselves should be protected against reverse polarity. HOWEVER, your light may not be. You would need to look at your light schematic to determine if it is reverse polarity protected.

Scott A. Novak


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## DrvLikHell (Aug 9, 2016)

On the topic of maximum current output, would this box be able to power two mostly equal, un-modified lights at the same time? I have two SecurityIng HD-016 lights and the six cell version of this box. I don't have the ability to test the draw of the lights and I also don't want to fry anything if the protection circuit in the box isn't working or wired correctly.


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## KennedyBacon (Jan 31, 2019)

Hi all! I've been scratching my head and looking around the interwebs for a good explanation to my question, but this tread seems to have some solid answers. I'm a complete novice to electronics, mA's, A, mAh, and all the rest. With that in mind, here goes: I just received the trustfire EB02 with the 4 battery slots, I have 4 samsung 30q batteries and a Revtronic BT40s as a light. Since I don't have an external charger, my question is: is it safe to charge the batteries inside EB02, and how long will it take? My charger's output says it's 8,4V 1000mA +- 50mA. The charger has an indicator light that goes green once the batteries are charged (tried it with other unspecified batteries of a borrowed light). Also, can I use this charger safely without overcharging the batteries, as I read somewhere these 18650 batteries are in danger of? You're answers will be much appreciated by this noob!


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## DrvLikHell (Aug 9, 2016)

KennedyBacon said:


> Hi all! I've been scratching my head and looking around the interwebs for a good explanation to my question, but this tread seems to have some solid answers. I'm a complete novice to electronics, mA's, A, mAh, and all the rest. With that in mind, here goes: I just received the trustfire EB02 with the 4 battery slots, I have 4 samsung 30q batteries and a Revtronic BT40s as a light. Since I don't have an external charger, my question is: is it safe to charge the batteries inside EB02, and how long will it take? My charger's output says it's 8,4V 1000mA +- 50mA. The charger has an indicator light that goes green once the batteries are charged (tried it with other unspecified batteries of a borrowed light). Also, can I use this charger safely without overcharging the batteries, as I read somewhere these 18650 batteries are in danger of? You're answers will be much appreciated by this noob!


I remember it being talked about before, basically the box will charge the cells fine, but it charges them together, so eventually they'll get unbalanced (unequal voltages) which could damage one of the cells in a pair when discharging. It's best to take them out and charge them in a charger that charges cells individually at least once in a while, so they get balanced again (every 5 times?). If you really don't want to buy a charger, there's a hack for balancing the cells without a charger mentioned in the bottom of another thread here. Just have to make sure they don't get put in wrong or you'll end up with things on fire.


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## KennedyBacon (Jan 31, 2019)

many thanks for your reply! That link is very helpful! Now I feel a little less worried when charging. I don't know how long it will take to charge them, but I'm leaving them on the charger until the light turns green. I can charge them in my mate's charger every 5 times for balancing until I get tired of this and get my own charger.


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## ledoman (Apr 17, 2012)

If you got quality cells then you would rarely need to charge them separately. If you have multimeter (DMM) you can check voltage of each cell from time to time and you'll know it very well. Balancing cells is simple as I wrote on linked post. With Samsung 30q I don't see much need to do it. It is more depended on different spring resistance in the box I would say.


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## andychrist (Aug 25, 2011)

*Nifty way to remove cells from TrustFire case when still attached to bike frame*









The Neodymium Refrigerator Magnets I bought are currently OOS but these acrylic ones are probably safer all around, no need to cover bases with electrical tape (to avoid any possible shorts) as I took care to do.

https://www.amazon.com/Nexlevl-Prem...600364&s=gateway&sprefix=Refr,aps,131&sr=8-28

This way during the mild part of the year I can either charge all the Pannies inside their TrustFire cases while still attached to my bike stationed outside the house (under 4' eaves) or easily bring the individual cells inside for rebalancing in my three XTAR VC4 jobbies, without having to undo any of those PITA Velcro straps.

Also should mention here that the 1-1/4" x 3/8" Black Window Seal Rubber Window Weatherstrip I applied to narrow sides of my 6-cell cases worked a treat, now those TrustFires really stay in place. (Had to apply a layer of 3M double-stick tape as well because the adhesive on the weatherstripping is pretty useless.)

https://www.lowes.com/pd/M-D-10-ft-x-1-1-4-in-Black-Window-Seal-Rubber-Window-Weatherstrip/3120623


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## Cat-man-do (May 16, 2004)

*@Andychrist;* Since you look to be mounting this to your frame have you have any problems with the light going out while bouncing over rough terrain? I've yet to use mine on my frame. I put mine in my hydration pack where it powers my Wiz XP-3 on the helmet ( when MTB'n )


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## andychrist (Aug 25, 2011)

Cat-man-do said:


> *@Andychrist;* Since you look to be mounting this to your frame have you have any problems with the light going out while bouncing over rough terrain? I've yet to use mine on my frame. I put mine in my hydration pack where it powers my Wiz XP-3 on the helmet ( when MTB'n )


No outages so far, Cat. And I don't have shocks on this bike, it's a pretty harsh ride and the roads around here are mostly terrible. Guessing the fact that the 6-cell TrustFire has springs both top and bottom has something to do with its improved performance over the 4-cell case.

Initially I'd planned on mounting frame bags onto my recumbent to hold the cases so that shock wouldn't be transmitted directly to them and also to avoid having to deal with their PITA Velcro straps all the time. But I couldn't find any bags that would fit both the front of my bike and the batteries as well, so went with the weatherstripping/direct frame mount. Actually this set up works rather well for me especially as my Ituo Wiz XP3 doesn't have functioning charge status LEDs while the Trust Fires have three stage indicators on which I can always keep an eye, with the cases exposed to view like this. And my new refrigerator magnets make it a cinch to get the cells out for balancing, though must admit it's kind of a pain unscrewing the 6-cell TF lids with the dual knobs so close together. Fortunately, should rarely have to do this.

I do have a couple of panniers in back of the bike where I can stash batteries to power my tail lights as well as a capacious seat bag with a long loop that can probably accommodate like three blinkies at once. Though the way that bag attaches it's kinda taut so not sure how well it mitigates impact, gotta check to make sure none of my clip-ons go flying off.


Bacchetta Light Setup by andyXchrist, on Flickr

Had originally been using my Wiz-XP3 on the lid too, Cat, with a KD 4-cell flatpack in my front chest jacket pocket. But the cables barely reached, making for an awkward combo that was also way overpowered for my needs. So the XP3 is now on the bars along side my XP2 (swapped in LEDDNA ellipticals) with separate battery packs for each secured to the riser. Got a 4000K KD BL2S for use on the lid in place of the Wiz, and its long cable combined with that of the KD flat pack in my jacket's flap pocket makes for a bulletproof setup with all the lumens I need for negotiating the kind of tight corners that my frame and bar lights might miss. XM L2 U3 bin is fantastic, noticeably better than that of the Ituos' 5000K IMHO.


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## andychrist (Aug 25, 2011)

These refrigerator magnets are slimmer than the first ones I bought, which allows more room for my clumsy fingers to reach inside the case. Not as intense attraction but still enough to pull cells up and of course easier to release them as well.

https://www.amazon.com/gp/product/B01B1XQV5M/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1


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## Cat-man-do (May 16, 2004)

andychrist said:


> These refrigerator magnets are slimmer than the first ones I bought, which allows more room for my clumsy fingers to reach inside the case. Not as intense attraction but still enough to pull cells up and of course easier to release them as well.
> 
> https://www.amazon.com/gp/product/B01B1XQV5M/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
> 
> View attachment 1246246


The magnet idea was a nice find. If you don't like removing loose cells by removing the box the magnet idea you had was smart. Personally I have a set of four wheel lights that are a PITA to deal with when it comes time to recharge the batteries. Basically I have to turn the wheel upside down and then bounce the bike till the battery ( single AAA ) falls out. While this was not too much of a problem with my regular road bike I now have the same wheel lights on my new commuter e-bike. Bouncing a 50 lb. e-bike ( need I say ) is a much more difficult task. Thanks for the Amazon link, I'll order a set myself when I place my next order.....in the mean time, time to charge the wheel lights again.....Oh! me aching back!


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## inu (Dec 12, 2020)

Hi,

Excellent thread. Scott, thanks for the detailed analysis. I've just received the boxes and would like to contribute a bit with some fresh information. The boxes are of the EB02 model (4 cells) but I presume it does not make a difference here.

According to my measurements, the battery state indicator (3 LEDs) works as follows*.

Green: Vbat ≥ 7.48V;
Amber: 7.48V > Vbat ≥ 7.0V;
Red (steady): 7.0V > Vbat ≥ 6.47V;
Red (blinking): 6.47V > Vbat ≥ 5.45V

The indicator works only when the USB output is turned on.

When Vbat < 5.45V, no LED is lit and both outputs are disconnected from the battery. So the over-discharge protection seems working fine. But consider the voltages before using a LiFePO4 cells.

*All the voltages are measured at room temp (25 degree C) with no load current.


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## Desertride (Nov 1, 2012)

Any advice on whether these boxes (I have the 4 cell version) can be used somewhat safely with unprotected cells? I just disassembled an old battery pack and have 4 perfectly good cells. Charging would of course be done on an external charger.


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## inu (Dec 12, 2020)

Desertride said:


> Any advice on whether these boxes (I have the 4 cell version) can be used somewhat safely with unprotected cells? I just disassembled an old battery pack and have 4 perfectly good cells. Charging would of course be done on an external charger.


This is exactly the box is designed for. Use unprotected cells. Just observe polarity with great care (the reason was explained early)


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## cartridleng (Jan 11, 2021)

inu said:


> This is exactly the box is designed for. Use unprotected cells. Just observe polarity with great care (the reason was explained early)


Hi!
I came here to ask the same question as *Desertride*

The thing is that TrustFire gives the info on the website
EB02 Battery Box

_Specical and Only for 4×18650 Li-ion rechargerable battery with protection PCB. _

Anyway, is then the charger the important part here when using unprotected cells?
I have a Nitecore D2 charger, any precaution I must take? (it has integrated reverse polarity protection btw)

What is the total capacity that I will have available for my SolarStorm X3 bike lamp if I put 4 of these batteries:
_"3.6V 18650 NCR18650GA 3500mAh 10A Continuous Discharge"_ in the TrustFire EB02 box?

Also has the TrustFire 4 cell version springs both at top and bottom?
There's contradicting info, here user *andychrist *says it doesn't
In this review it says it has Бокс для аккумуляторов 18650 | fatpanda.ru
A confirmation from a recent owner of the box would be good

Sorry for the noob questions!

Thanks in advance


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## inu (Dec 12, 2020)

cartridleng said:


> _Specical and Only for 4×18650 Li-ion rechargerable battery with protection PCB. _


Notice where this sentence is. It's not in the specification text, but it's printed on the packaging cartoon. That's an example of smart strategy. Such statement protects local dealers from the lawyers. Should a careless customer insert a cells in wrong polarity, the chances are the whole thing will melt or even catch fire because of excessive heat development. Otherwise it works just fine with an unprotected cells.



cartridleng said:


> I have a Nitecore D2 charger, any precaution I must take? (it has integrated reverse polarity protection btw)


Not sure if this charger has any relation to the battery box...



cartridleng said:


> And what is the total capacity that I will have available for my solarstom x3 bike lamp if I put 4 of these batteries:
> "3.6V 18650 NCR18650GA 3500mAh 10A Continuous Discharge" in the trustfire EB02 box?


With four cells loaded, in theory you will have a battery of 7.2V (3.6*2) with the capacity of 7Ah (3.5*2). Or, you can load just two cells to have a 7.2V 3.5Ah battery.



cartridleng said:


> Also has the trustfire 4 cell version springs both at top and bottom?


Yes there are four springs in the deep hole as well.
BTW in fact, the boxes are splash-proof and not water-proof. The cable entry and the screw are not sealed. The Technical Detail tab on the product web page specifies ingression protection grade IPx4, which seems more plausible.


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