# Battery Build



## The_Stig (Jul 24, 2008)

so I need a new battery for my light. What would I need to build a 5400mah 7.4v Lithium Ion rechargeable battery?


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## Ofroad'bent (Jul 10, 2010)

You could use one of these holders:








2S2P 18650 Battery Holder [18650 2P2S] - $11.00 : Easy2LED.com, The store for LED DIY

and some unprotected cells.

or you could get a battery pack on eBay form FMA battery and waterproof it with some heat shrink. $40 with connectors and free shipping. Decent Sanyo cells.

( Can't post the link here, MTBR automatically removes it)

search for item 220614567832 on eBay


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## sergio_pt (Jan 29, 2007)

Plastic Battery Storage Case Box Holder for 4 x 18650 Black with 6" Wire Leads

less than 3 dollars at ebay instead of 11 + shipping...


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## realconspiracy (Jan 22, 2011)

In the product linked above there is no built in PCM to prevent cells from over charging or over discharging. Prepare for fire.


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## sergio_pt (Jan 29, 2007)

not if you have protected cells, It's the best solution IMO...


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## sergio_pt (Jan 29, 2007)

If the battery pack protection circuit fails, you'll have a big blow! 
If the cell protection circuit fails, you'll have a smaller blow...


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## realconspiracy (Jan 22, 2011)

Any reason why one is better than the other?


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## pimpbot (Dec 31, 2003)

Also, put a charge regulator circuit board on there so it divides the voltage up properly between the cells. If you don't one bank of cells will get full and cut itself off, leaving the other bank less than fully charged.

IIRC, I've seen them for like $5 or $6 or so.

Or... make it so the cells can be popped out and charged individually in another charger.


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## realconspiracy (Jan 22, 2011)

Can you just use a balance charger instead of adding an additional pcb into the mix?


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## OldMTBfreak (Apr 8, 2006)

I would run 2s2p battery using 18650 cells. This will about 36 watt/hours. Your easiest option is to buy cells with tabs and solder up a pack. Use these these cells Li-ion 18650 Cylindrical Rechargeable Cell: 3.7V 2600mAh (9.62Wh). Use this PCB Protection Circuit Module (PCB) for 7.4V Li-Ion Battery Pack (8A limit) with Fuel Guage Socket. If want automatic balancing then buy this PCB Protection Circuit Module (PCM) with Equilibrium Function for 7.4V Li-Ion Battery Pack (20 Amp limit, PCM-L02S20-265). That should fix ya right up. This is how I make my batteries. While you're at the battery site, get some shrink tubing to wrap the battery. I would switch up to li-polymers for higher current batteries. Even though I feel safe in using these cells in 2s3p configuration. Same PCB's can be used, capacity would be 56 watt/hours. James


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## ThinkBike (Jun 16, 2010)

I'm with Ofroad'bent on this one. The eBay auction 220614567832 from the seller FMA_Direct seems to be a fair deal and no soldering needs to be done on your part. I don't think you'll find a pack put together with a PCM and a set of 4 quality cells for a price like this.

If you do like to put together your own packs, then OldMTBfreak has given you some good guidance. Search the threads for how to correctly solder up a pack on your own. Youtube also has some decent videos on how to solder your own pack.

As OldMTBfreak has pointed out, if you make your own pack, you can choose to build a larger capacity 2s3p pack. If you have a powerful light or you require longer run times, then building a pack might be your best bet. 

How much capacity do you need? I said "need" because you probably don't want to carry around a larger pack than necessary.


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## Ofroad'bent (Jul 10, 2010)

I've found FMA will build me whatever I want, more or less. They've done 1S4P, 1S2P, 2S2P. The Sanyo batteries they use seem to be pretty good, and service is fairly quick. I suspect they supply a lot of other vendors.

The connectors they use aren't waterproof, but with some heat-shrink tubing over them they seal nicely with Magicshine connectors.

I've built battery packs with protected batteries in the cheap holders, but the wiring was too light and needed redoing with decent wire.

I've also used the protected holders with unprotected cells, but it cost more by the time I added connectors. At least I have the option of changing cells easily in future.

Best/ simplest waterproofing I've found so far? 
Wrap them in electrical tape (Self fusing silicone is best but more expensive)

Cover in heat-shrink tubing with a bit of extra length, shrink down, and fold the end down tight while still hot. 

Once cool, plasti-dip the end, and paint some plasti-dip on around the connector.

It's faster and possibly stronger than doing multi coats of plasti-dip for the whole pack.


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## Rich_SC (Oct 10, 2009)

I've been using lipo's from Hobby king...they have been great, dependable and dirt cheap. I do add pcb protection for use on non-taskled driver'd lights. And they have a warehouse now here in the US so I can get batteries in a few days.

Every time I think of going to 18650's I end up back to lipo's because they are half the cost.

Here's the battery I use for 7.4v lights... 6000mAh and $28 (pcb is an extra $4)

HobbyKing R/C Hobby Store : Turnigy nano-tech 6000mah 2S 25~50C Lipo Pack (USA Warehouse)


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## Ofroad'bent (Jul 10, 2010)

Does hobbyking sell the PCB?
Any trouble waterproofing?
I'm thinking the hardcase LiPos might be safer, and a good bet for my friends who want to drive the light at 3A a lot.


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## Rich_SC (Oct 10, 2009)

HobbyKing's US warehouse only has batteries and I'm not usually willing to wait for the China shipment. I found PCB's from a couple different US based companies. The latest one I used was All-Battery.com. Cheap and fast shipping too.

I wouldn't get the hardcase. You need access to the battery to install the PCB. RC people run these batteries way harder than we do with lights.

I usually remove the huge 10awg cables on the HobbyKing lipo's then wire up the PCB using the attachments for the balance leads. Just need to be careful not to short out anything as usual. I then wrap everything in silicone tape (F4 tape) and stick it in a waterbottle as a holder. Waterproof enough for me. I just got a bunch of batteries in. I'll do a write up on how to do this. I actually had a hard time finding info on this.

I also use their balance charger. The multifunction chargers you can get are usually too complex for people I sell lights to (sell meaning friends pay me for parts and I build them). I like it simple and this one is just plug and play. I like being able to balance charge the lipo's and it's very simple to use.

The charger:

All-Battery.com: Tenergy 1-4 Cells Li-PO/Li-Fe Balance Charger

The PCB's:

All-Battery.com - Rechargeable batteries & Chargers - PCB/PCM/BMS for Li-ion and Li-Polymer Battery Packs


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## ruscle (Jun 19, 2011)

Waterproof it by using shrink tube then plastidip


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## Dalistro (Sep 21, 2011)

Hmm are there any disadvantages in using the polymers instead of the ions for light(LED lol) usage (under 3A)? 
From reading around I've gathered that polymers are better at higher discharges due to lower internal resistance.

Since I still see alot of people here using 18650 packs, I must be missing something!


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## Rich_SC (Oct 10, 2009)

Most people talk about the higher risk of fire and there has been some well documented cases that usually get posted (cars burning etc). I think if they are protected by either the PCB or with a taskled driver they are just as safe as li-ion. Most of the danger happens when they are either overcharged or over discharged. I supply a lipo safe bag for charging just in case. It's a few bucks from China.


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## Ofroad'bent (Jul 10, 2010)

If you perforate a LiPo with a nail or something it can catch fire too. That's why I was wondering if simply shrink-wrapping and plasti-dipping is sufficient. Inside a water bottle should be fine.

Rich, not meaning to hijack, but how would you set this up for 3.7v, 1S?

I'm assuming you use this board for 3.7v.
All-Battery.com: Protection Circuit Module (PCB) for 3.7V Li-ion Battery Pack (2.95A cut-off)
The only larger capacity 1S Batteries at Hobbyking are hardcase which have no balance plug. Do you just wire the huge leads to the B+ and B- and the light connector to the P+ and P-?


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## zemike (Sep 3, 2007)

Rich_SC said:


> Every time I think of going to 18650's I end up back to lipo's because they are half the cost.


True, especially if you factor in the price of good 18650 cells.
The drawbacks of the lipos are:
1) no integrated protection
2) heavier than 18650

I have one 5000mAh 7.2V LiPo pack which powers 6 XP-G @1.5A, that's more than 30W and there are no problems with capacity or voltage sag.


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## zemike (Sep 3, 2007)

sergio_pt said:


> Plastic Battery Storage Case Box Holder for 4 x 18650 Black with 6" Wire Leads
> 
> less than 3 dollars at ebay instead of 11 + shipping...


That will give 4S
DX sells similar holders for 2 cells which give 7.4V, just wire 2 of them in parallel to make a 7.4V "5000mAh" holder


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## Rich_SC (Oct 10, 2009)

Ofroad'bent said:


> If you perforate a LiPo with a nail or something it can catch fire too. That's why I was wondering if simply shrink-wrapping and plasti-dipping is sufficient. Inside a water bottle should be fine.
> 
> Rich, not meaning to hijack, but how would you set this up for 3.7v, 1S?
> 
> ...


I don't use any 3.7v 1s batteries for my builds but if I did I would just buy the individual lipo cells and then wire up the pcb protection you linked to. Yes, battery goes in to pcb and P+/- goes to the LED

You can cover the finished battery with some plastic to give some impact/puncture resistance.


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## Bryank930 (Jun 12, 2006)

This seems to be a pretty good deal: eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

They're all-battery.com packs for basically 1/2 price and WAY less for shipping.


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## borrower (Feb 26, 2011)

Bryank930 said:


> This seems to be a pretty good deal: eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices
> 
> They're all-battery.com packs for basically 1/2 price and WAY less for shipping.


If you trust the folks at budgetlightforum.com (and I do), then you might think that these batteries are the offspring of a fire at Battery Junction. Some of those batteries are showing corrosion under the wrapper (maybe they got wet?). It *does* sound like the ebay seller stands behind their product, but best to make a completely informed decision.


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## Bryank930 (Jun 12, 2006)

borrower said:


> If you trust the folks at budgetlightforum.com (and I do), then you might think that these batteries are the offspring of a fire at Battery Junction. Some of those batteries are showing corrosion under the wrapper (maybe they got wet?). It *does* sound like the ebay seller stands behind their product, but best to make a completely informed decision.


I've browsed around that site before. They seem to like the particular seller I linked to above (marrs inc). I'm not worried:thumbsup:

Wasn't the fire back in 2010 though??


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