4s hardcase LiPo. how to remove a cell?

Deutch420

Deutch420

100 W
Joined
Jul 9, 2011
Messages
187
Location
Central NJ
I have about 9x 4s batteries, all with 3 perfect cells and 1 bad. Ide like to remove the bad cell from each pack, so i can use the remaining 3s packs for a trolling motor 12v battery pack for my canoe.

How exactly do I go about this? I've opened the packs, and it seems like there are 2 circuit boards per 4s pack. how do i remove the bad cells from these boards? If the bad cell is in the middle of the pack, will it still work? basically, all the cells are glued together, so how i would remove one from the group??. And they're soldered to circiut boards (2 cells per board. 4 cells per pack). I can determine what cell # is bad, and then follow the color wire from the balance tab to the individual cell, so i know which one is bad.

i just dont know how to remove the bad cell from the group physically. im afraid ill damage the cells peeling them apart bc they're glued, which would blow up in my face. im also unsure how to remove the battery from the "circuit boards". What do i cut? does anythign need to be repaired after removing the cell?

Thanks
 
My experience so far has been that the bad cell is on the end of the pack. Using a soldering iron, I just move the main discharge wire from the end of the last cell, to the end of the next to the last cell, leaving all else in place.

Nothing need be cut, the boards if any left intact. Then slowly discharge the end, defective cell. at 0v or close to it, it's now safe.

I have peeled that end cell off too, but didn't like the wrinkles it left in the next good cell. Warm it before you peel it off if you do. Better to try to unstick that tape when warm, than when the pack is very cold.

If you have duds in the middle, then I'd be inclined to peel off the two with the bad cell, possibly damaging that one good cell. Not bending the good two cells up I mean, as you peel them apart. Be sure when you cut or unsolder the good cells, that you leave the soldering tab on the good two. You can cut the aluminum tab short on the bad cell of course.
 
I often use rubbing alcohol and credit card to soften the double sided tape and separate pouches with minimal damage. I wouldn't worry too much about blowing up in your face but be prepared. I wear sturdy/heavy clothes and keep a bucket of sand handy whenever I'm messing with RC Lipo surgery, reconfigurations, etc.

As far as the circuit boards - I haven't dismantled hardcase yet so I'm not familiar enough to help. Maybe a picture of what you're talking about would help trigger some ideas for a sensible approach? I know some newer RC Lipo have gone to spot welding pouch tabs so that's another complication you may be facing?
 
i used my table saw and cut a kerf around the top just below the lid just deep enuff so the blade did not go all the way through the case, but almost, so it could be peeled apart. then removed the top and then cut along the seam with the kerf deep enuff to cut through the plastic but not the pouch. for 4S the joint should be between pouches.

then i pulled the two sides of the case off of the pouches. they have double sided foam tape across the middle of the pouches holding it to the inside of the case.
 
Do it somewhere you can toss them. Not inside on the kitchen table. Give yourself an escape route, just in case. They are very alive.
 
To separate cells, take fine fishing or nylon thread and slide it beetween cell pulling with you hands from side to side, use vaseline and go behind wih some card to prevent them to stick again.
 
I would leave the bad cell in, and just discharge it. Then trim the balance plug down to 3s and move the big wire along a cell. That is if the end cell is faulty.

They have not had boards in them for a while. My oldest are 3yo and don't have them. I have to question how much life is left in them. I'm not sure I would bother.
 
I open the cases by dremeling couple corners then pyring open with a screwdriver, being very careful.

I recorded the cell replacing process when I did it-

https://youtu.be/4OZd7OIuQbo
[youtube]4OZd7OIuQbo[/youtube]

Also worth saying, these packs are only about $25/piece, so it might just be worth buying a whole new pack.
 
Metallover said:
...., these packs are only about $25/piece, so it might just be worth buying a whole new pack.
Click to expand...
Not that easy.....he has 9 packs, and he want 3s anyway !.... :shock:
Deutch420 said:
I have about 9x 4s batteries, all with 3 perfect cells and 1 bad. Ide like to remove the bad cell from each pack, so i can use the remaining 3s packs for a trolling motor 12v battery pack for my canoe. ....
Click to expand...
 
Not worth it, if the 9 packs are like, 3 years old. But if they are fairly new, then I'd scavenge the cells for sure.

That do it outside advice is very good, but if just moving the big wire from one terminal to the other, I wouldn't worry. Prying apart the tape, do that outside because you could set off a cell bending it enough.
 
An idea, you could probably run the trolling motor off 4s and be ok? Fully charged SLA is 14.4V.. 4s packs will be 16.8 fully charged, will probably run at about 16V. The motor will run hotter and the life will be a bit shorter, but depending on what you're doing with this motor it might be a great option. I'm not sure how the motor is controlled, but you could limit the throttle 4s and it would last just as long?

quote form a thread where a guy is trying to run 48V on a 36V motor - http://www.boatdesign.net/forums/hybrid/over-volting-dc-motor-48861.html
The motor can be harmed only by heat, which is the product of current and voltage (Watts), multiplied by the duty factor.

Assume that the motor can operate continuously on 36 volts, drawing 10 amps and generating 360 watts.
At 48 volts the current rises to 13.3 amps, so 48x13.3= 638 watts. To prevent the motor from burning out, the duty factor must be reduced to 360:638= 56% !!
That means the motor should be switched off 44% of the time.

Whether or not the controller survives depends on the quality of its output stage. The increase in current alone is not significant, but at 48 volts there are spikes of nearly 100 volts that may prove fatal if the output stage is only rated at 80 volts.

Is it a good idea? No, it is not....
Click to expand...
 
Metallover said:
An idea, you could probably run the trolling motor off 4s and be ok? Fully charged SLA is 14.4V.. 4s packs will be 16.8 fully charged, will probably run at about 16V. The motor will run hotter and the life will be a bit shorter, but depending on what you're doing with this motor it might be a great option. I'm not sure how the motor is controlled, but you could limit the throttle 4s and it would last just as long?

quote form a thread where a guy is trying to run 48V on a 36V motor - http://www.boatdesign.net/forums/hybrid/over-volting-dc-motor-48861.html
The motor can be harmed only by heat, which is the product of current and voltage (Watts), multiplied by the duty factor.

Assume that the motor can operate continuously on 36 volts, drawing 10 amps and generating 360 watts.
At 48 volts the current rises to 13.3 amps, so 48x13.3= 638 watts. To prevent the motor from burning out, the duty factor must be reduced to 360:638= 56% !!
That means the motor should be switched off 44% of the time.

Whether or not the controller survives depends on the quality of its output stage. The increase in current alone is not significant, but at 48 volts there are spikes of nearly 100 volts that may prove fatal if the output stage is only rated at 80 volts.

Is it a good idea? No, it is not....
Click to expand...
Click to expand...
Right. My SeeDo scooter lasted under 10 minutes on 4s Lipo, before all plastic internals where melted and winding of the motor shorted. But, fun childrens had is priceless! :lol:
 
Hillhater said:
Metallover said:
An idea, you could probably run the trolling motor off 4s and be ok? ....
Click to expand...
How exactly does that help ?
All his 4s packs have one dead cell !
Click to expand...
I think, he meant 3s, which is the most logical outcome.
He could just discharge bad cell to 0V and short solder on the PCB and rearrange balance wires. 3s will be much more motor friendly, starting discharge at 12.6V and ending at 10.5V, exact LA 100-0% battery range. Notice at LVC it will be 3.5V/cell, well in the recomended HK LiPo cutoff. What do you think? :)
 
what makes him think the pouch is bad anyway

it only took me less than a minute to cut open the cases on the hardcase packs i opened with the table saw. it should not be a problem. won't know if they are puffed until the case is off.
 
Deutch420 said:
I've opened the packs
Click to expand...

I don't think the issue is opening the hardcase but how to handle the cell connections. Honestly, without pics hard to say how to approach since HK has changed things over the years.

Meanwhile, I hope Deutch is simply enjoying abundant 420 and will get back to us when possible...
 
Thanks for all the replies guys! Seems like some of you have been answering others for me! perfect! :D

The batteries dont have that many cycles on them, so i know the cells have some good life in them still.

To those asking how i know they're bad. On a charge to 4.15, 3 cells hold 4.14-4.15 perfectly, and the other cell doesnt go over 2.5v. I noticed it right away and removed the bad batteries from my pack and have no tried charging again since. So the bad cells are already fairly discharged, just not to 0v

The video was pretty helpful. i guess i have to seperate them with fishing line or a credit card, along with some rubbing alch.

You were all right that it appears to be the outside cell on all 9x bad batteries. So i suppose i could just remove the balance lead, and move the main wire 1 cell up like suggested.
 
Hillhater said:
Suspicious of always the same end cell ??
How were you charging them ?...balance leads, or bulk charging ?
Click to expand...

Balance leads always. With a balance charge at the end, never rushed or removed from the charge prematurely. I charger 306 with a meanwell 1000. I too am suspicious of it always being the outside cell. But all the packs are the same, where I realised the balance charge was taking much too long, so I remove from charge and 2 days later the 1 cell was 3.8v vs the others at 4.14- 4.15v so I knew something was up. Now, months later (they've been sitting. theyre from an older, lightly used project) its 2.8v and the others are 4.12-4.14. So the other cells seem healthy.
As far as the pic goes, it keeps telling me invalid format. I'll have to try with a camera and not my cell.
 
I have over 40 other lipo batteries between my other bikes. All cells are fine after hundreds of cycles. And has worked fine for 2+ years. Shit, I still have 6s batteries holding 4.1v charges and they're over 4 years old with 400+- cycles. They work fine. I have the same 4s hardcase packs in my main bike. That's worked flawlessly for 2 years and I hit those batteries with 80amps. Its not the charger or harness or neglect.
 
so when you put this 6S pack in the RC charger does it also read low on that same channel? are all of the low measurements in the same location or does it happen on each end of the various packs and not the one spot? did you measure with an accurate voltmeter? did you do a capacity test by discharging in order to demonstrate that the pouches are all lower capacity than the others? i saw no analysis, just the statement that the voltage was low. observation is not analysis.
 
dnmun said:
so when you put this 6S pack in the RC charger does it also read low on that same channel? are all of the low measurements in the same location or does it happen on each end of the various packs and not the one spot? did you measure with an accurate voltmeter? did you do a capacity test by discharging in order to demonstrate that the pouches are all lower capacity than the others? i saw no analysis, just the statement that the voltage was low. observation is not analysis.
Click to expand...

theyre 4S packs, not 6S. but if your asking if a GOOD 6S pack has the same bad cell readout via the balance tabs OR voltmeter, no it doesnt. Also, if your asking me if the cell readouts match, the answer is yes. I have an iCharger306, voltmeter and aCellLog 8M. they all corrilate and give the SAME EXACT individual cell voltage. again i have over 40 GOOD battery packs still, that are used on the SAME charger and SAME harness with hundreds of cycles and no issues. Thats why this is a clear cut issue for me. its just 1 bad cell in each of the 9x 4s packs i have. im not sure HOW it happened, but this is the end result, either way. Also, its not the same cell # in each battery that is bad, however, it IS always the OUTSIDE battery. With that said, some of the bad batteries have cell1 bad, some have cell 4 bad. None are middle cells that went bad. So maybe it was physical damage that did it?
i charge the packs to 4.15v, the one cell doesnt hold voltage or even charge above 3.8v while the other 3 cells are at 4.15. yes a volt meter confirms this along with my cellLog and icharger. I dont understand why i need more analysis. clearly the 1 cell is bad. my poor icharger will sit and try to balance it for days if i let it. the one bad cell will not go above 3.8v. and 1 day after charging to 3.8v it dropped under 3v. it was at this point i decided to remove them and NOT attempt to recharge them. Thats when i made this thread to figure out how to remove them from each other, thus making 9x usable 3S packs.

Either way, i have decided to not bother with these packs. If anyone is local and wants them, PM me. Ide take 75$ for all them. there are 27 good cells with about 100 cycles on them. I also have 2 old 6S packs. combined there are 9 good cells in those 2 packs, but they have seen 400+ cycles so im not sure how much life is left in them. ill add those 9 cells for free.

OR

if someone wants to show up and turn these into 3S packs for me, i would pay for your time. Just PM me
 
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