# LiPo protection circuit problem



## formantjim (Feb 24, 2008)

Have recently purchased from Hobbyking some 14.8volt LiPo 4000mA/hr batteries unprotected tested them without protection and are true to the specification.
I make quite a few of my "Pipe Lights" for friends and since the demise of the Fatman driver from Taskled which I used a lot in my builds I have changed to different drivers that are buck instead of boost so the battery voltage needed to change to 14.8volts.
So I purchased from All-Battery some 4S protection circuits to be on the safe side when providing friends with batteries.

On wiring them up as as per the diagram
http://forums.mtbr.com/attachment.php?attachmentid=594429&stc=1&d=1296317217

I get no output whatsoever from P- and P+ and the charger says open connection!

I have the balance wires as shown and the P- and the P+ coming from the battery.

Please help me here to understand what I'm doing wrong.

Thanks


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## kwarwick (Jun 12, 2004)

formantjim said:


> Have recently purchased from Hobbyking some 14.8volt LiPo 4000mA/hr batteries unprotected tested them without protection and are true to the specification.
> I make quite a few of my "Pipe Lights" for friends and since the demise of the Fatman driver from Taskled which I used a lot in my builds I have changed to different drivers that are buck instead of boost so the battery voltage needed to change to 14.8volts.
> So I purchased from All-Battery some 4S protection circuits to be on the safe side when providing friends with batteries.
> 
> ...


For that diagram to work, you should be charging and discharging through the B- and B+ contacts, not the P- and P+.


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## MtbMacgyver (Jan 23, 2007)

From your description, I can't see anything wrong. Have you taken a meter and measured the voltages right on the terminals on the PCB. Between every pair of terminals, you should see the right voltage for a single cell with the right polarity. Test (B-,B1+), (B1+,B2+), (B2+,B3+), (B3+,B+). Then for good measure, test B-,B+ and make sure you have full pack voltage with the right polarity. 

One thought, they make both a 3S and 4S protection board using the exact same PCB. For the 3S version, the B3 terminal isn't used. If you happen to have the 3S version because you ordered incorrectly or they accidentally shipped the wrong one, you'll get the exact behavior you describe. That's because the 3S version expects to see a single cell voltage between B- and B2, but when it's wired in a 4S pack configuration it sees the voltage of 2 cells. You can identify the 3S version because there will be unfilled spots on the PCB for a resistor and a capacitor. You can convert between the 3S and 4S version of the board by populating the missing components and also changing another resistor on the board from 0 ohm resistor to a 1k ohm resistor.


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## MtbMacgyver (Jan 23, 2007)

kwarwick said:


> For that diagram to work, you should be charging and discharging through the B- and B+ contacts, not the P- and P+.


That's incorrect, you should be charging and discharging through the P+ and P- terminals. That's how the protection PCB provides protection. It controls the charge and discharge going into the actual cells.


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## kwarwick (Jun 12, 2004)

MtbMacgyver said:


> That's incorrect, you should be charging and discharging through the P+ and P- terminals. That's how the protection PCB provides protection. It controls the charge and discharge going into the actual cells.


I guess that diagram is what threw me. He shows a connection coming off the battery that ties P- and B1+ together and then another that ties P+ and B3+ together which of course wouldn't work so probably those lines are supposed to pass over the P- and P+ connections.


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## formantjim (Feb 24, 2008)

Thanks for all the replies and to answer the questions here goes.

I have measured the voltages as MtbMacgyver mentions and yes I get the voltages of the individual batteries ie B-,B1+ etc and the correct voltage is as expected.
Yes it is the 4S version I bought 4 of these so replaced it with another the same result no voltage between P- and P+.
When connected to the charger via B- and B+ it does indeed charge but never finishes like it does without the PCB and just stays at a final voltage across the battery of 15.5 volts instead of finishing the charge at 16.8volts.


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## kwarwick (Jun 12, 2004)

Is this the board you are using? http://www.all-battery.com/protecti...s148vli-ionli-polymerbatterypack12alimit.aspx

The wiring diagram for that board shows that you charge and discharge through the P- and P+ contacts.


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## formantjim (Feb 24, 2008)

This is the one I'm using.
http://www.all-battery.com/protecti...nbatterypack4cellswith65alimit-lipcb14v4.aspx

I'm trying something at the moment as what I think is happening is when I connect the pcb to a fully charged battery 16.8V it somehow blows something as it is way over the limit set by the board.

I'm draining a battery to about 12 volts then I shall connect a new pcb and will report back.


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## kwarwick (Jun 12, 2004)

formantjim said:


> I have the balance wires as shown and the P- and the P+ coming from the battery.


Just want to confirm that you don't have the thick + and - wires from the battery connected to the P- and P+,  because that would be wrong. P- and P+ is where you attach the load (your light, or whatever) or the charger when recharging.

The vendor should be ashamed of such a poorly drawn and confusing diagram! I've created a wiring diagram that hopefully is much clearer:


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## HEY HEY ITS HENDO (Feb 23, 2008)

> when I connect the pcb to a fully charged battery 16.8V


yes i think i would have the battery pack at about 15v not 12v !!



> The vendor should be ashamed of such a poorly drawn and confusing diagram! I've created a wiring diagram that hopefully is much clearer


thats much more like it!


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## MtbMacgyver (Jan 23, 2007)

All the input voltages to the S-8254 chip used on that board are rated up to 26 volts. 16.8 volts is not a problem and is a normal voltage for a 4 cell pack. The high voltage cutoff on that board is 4.35v per cell which is a total pack voltage of 17.4 volts. I've used that exact board many times in battery packs. I've never had a problem.

When you first connect up the board, it will initialize in a protected state and you won't read any voltage on the P- and P+ terminals. You have to apply a charge voltage, typically 16.8 volts, to the P- and P+ terminals to initialize the board. Make sure you have your charger programmed correctly. It must be pre-configured for the right number of cells and output voltage. If it's in an automatic mode where the charger tried to determine the specifics of the pack, it won't work. That's because the charger won't read a voltage until the protection board is initialized, and the protection board won't initialize until it sees a charge voltage. Measure the output voltage of your charger before you connect it to the pack with a meter. If you don't see 16.8 volts, then it's not going to initialize the protection board. 

I'm also wondering now if you do have it wired up correctly. A hobby lipo 4S pack has 2 sets of connectors. A 5-wire balance connector and thicker main power leads. The thicker main power leads need to go to the B+ and B- on the protection board. You can make the B1+, B2+, and B3+ connection to the three middle wires in the balance connector on the pack. The two outside wires in the balance connector should not be used. Electrically they are the same as the thicker main power leads, but they are not intended to carry the full discharge current. That's why they shouldn't be connected to the B+ and B- leads on the protection PCB.


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## formantjim (Feb 24, 2008)

OK update the first board as you see here
http://forums.mtbr.com/attachment.php?attachmentid=594540&stc=1&d=1296345791
the component on the left is the sense resistor which has a crack in it and is open circuit hence the reason for no continuity from B- to P-!

The second board I installed must have had some other electronic fault as after installing the 3rd PCB it now charges correctly on the charger and reads the voltage correctly. It is still on the charger as we speak so only time will tell if the charger finishes at the correct voltage and balanced cells.
I'm using this charger.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11341

An excellent charger have used before with great results.

Thanks for the info regarding the board being initialized before it will function.


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## Itess (Feb 22, 2009)

formantjim said:


> It is still on the charger as we speak so only time will tell if the charger finishes at the correct voltage and balanced cells.


Does this board have balancing function? There's nothing about it in the description.


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## formantjim (Feb 24, 2008)

I have no idea as there was no information with the PCB's but the charger is a balance charger.
Went out this evening and just put the battery on charge again to see if it charges OK looks good at the moment.


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## emu26 (Jun 23, 2008)

A couple of questions, and sorry if I have missed it elsewhere or am asking questions once the horse has bolted.

Why didn't you use a maxflex driver instead of the buck drivers requiring bigger / new batteries?

Are you still using a taskled driver, if so and you have a good quality balance charger, why are you worried about the circuit protection?

That's not good that two out of three boards from all-battery have arrived DOA.


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## formantjim (Feb 24, 2008)

Update! The PCB works and shuts the supply off to the battery but only charges the battery to 15.1 volts not the 16.8 volt without protection.

To answer Emu

I have used Maxlex drivers before but a simple centre off switch is my preference and cost.

I use a modified Kennan driver at $3.99 each can't beat that!

I would never supply anything to my friends that could cause injury and also with the Kennan driver it has no warning at all.

Now to test the low voltage protection will update you all later.


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## formantjim (Feb 24, 2008)

Just an update have managed to make 2 battery packs with protection PCB's 2 out of the 4 PCB's faulty.
The charger is a balanced charger and charges both batteries to 15.1 volts then it open circuits itself as indicated by the battery charger. On disconnecting the charger and reconnecting it then will charge to it's normal 16.8 volt cut off. Bit of a pain when you think you have charged the battery only to have to return to finish it off is this normal?
The protection circuits work well cutting the supply off at 12.3 volts so I'm happy about that not so happy at the 50% failure rate.


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## kwarwick (Jun 12, 2004)

formantjim said:


> Just an update have managed to make 2 battery packs with protection PCB's 2 out of the 4 PCB's faulty.
> The charger is a balanced charger and charges both batteries to 15.1 volts then it open circuits itself as indicated by the battery charger. On disconnecting the charger and reconnecting it then will charge to it's normal 16.8 volt cut off. Bit of a pain when you think you have charged the battery only to have to return to finish it off is this normal?
> The protection circuits work well cutting the supply off at 12.3 volts so I'm happy about that not so happy at the 50% failure rate.


Perhaps this protection board is not meant to be used with a balance charger? It might be worth trying another charge without the balance function enabled to see if that's the case.


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## klynk (Apr 18, 2010)

Itess said:


> Does this board have balancing function? There's nothing about it in the description.


I've got clone of this charger (200W) - it has balancing function, and it works fine.


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## HEY HEY ITS HENDO (Feb 23, 2008)

Itess said:


> Does this board have balancing function? There's nothing about it in the description.


klynk, ..ltess was questioning the circuits boards ability to provide a balance function as well as charge/discharge protection
i`m certain there is no balance function on this board


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## formantjim (Feb 24, 2008)

Well according to the specifications it does some form of control internally but still needs a balance charger for correct operation.
http://www.all-battery.com/protecti...nbatterypack4cellswith65alimit-lipcb14v4.aspx.
It all works well so I'll move on keep on building new lights.


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