zero volt and cell count error ??

izeman

izeman

1 GW
Joined
Jun 21, 2011
Messages
5,131
Location
Vienna, Austria
i ignored (or missinterpretated) the low voltage alarm and ended up with one "dead" cell in one of my 6s zippy packs.
i connected the pack to several chargers, and all of them showed 5s packs. then i tried to charge them (0.1A only) to see what happens. of course the pack was put in a lipo safety bag.
this if what the chargers show. one cell down to 0.00v ??? and one missing:

1933,zerovoltWV6OO.jpg


anyway to revive that pack?

ps. there was no physical damage done to the pack.
 
Peel the shrink wrap and tape off the top of the battery, and get acess to the pcb board. There you will be able to see any disconnected balance wires, and verify the voltage of each cell. Don't bother to peel the whole battery, just carefully cut away the top. Easy does it, if you use a razor or knife, cut away from the cells for sure. I find a toenail clipper or very small wire cutter handy for starting the cut on the shrink wrap.

Anything discharged below 2.7v is a fire hazard.
 
did unsolder the cell, and measured again. still 0V and 2Ohm resistance. i think i will keep the other 5 perfect cells just in case on cell in another pack dies, and recycle the dead one. any other suggestions? i think i can't buy a single cell like the one in my pack to revive the whole pack, can i?
 
Well darn, I was thiniking it would just be a wire pulled loose. You can keep that pack for spare cells, run it one cell smaller, or buy a smaller pack, like 2s or something to get a new cell from.

I tend to just get a new pack since that is so easy. Then put the old one aside for later messing around with.
 
yep. i looked like a loose wire. i really can't imagine how a cell really could reach ZERO volt. normally also my oldest nicd cells have some remaining voltage. so what ...
i will keep the pack, as all other cells are in good shape.
i will see to buy a 2s pack, so i have one cell to use, and one spare. do you know if the cells used in zippy 2s packs have the same form factor?
 
yep, same form factor if you are getting the same AH, same C rating, and same brand given that they haven't switched up the formula recently.

And if you're looking for more AH, you may as well buy some more 6S packs. It is inevitable that you will get a pack with a dead cell in it. That will be your spare cell pack.
 
I would say that you need to replace it with a 25C. Funny things will happen when cells have different resistance levels in a series strand... it will certainly lead to disbalance and uneven wear over a long period of time.

If you absolutely have to.. i'd go with a 30c.
 
I wouldn't even mix brands. I originally had zippy's, then added some turnigy's. They act a bit different, and are a bit different physical size.
 
Replace the whole pack with anything you can get in stock, that is equal or higher c rate and the same ah. I don't hesitate to mix c rates or brands, provided I am charging each type seperately. I wouldn't slot in a new cell into that pack from any other kind.

Nothing is in stock at all in identical brand and c rate? No 2s or 3s packs at all?
 
nope. no 25c available at all. that's all they got. i have to look @european warehouse, because p&p + customs for one cell from hk would be an overkill.

1943,zippyEX53M.jpg


i found a 3s in US warehouse for $28.99 pls $9 p&p. omg. is it worth it? i'll give it a try. $28.99 = <22€, so there will be no customs tax.
 
sorry. i still got one question:

some of you mentioned that mixing different brands is a bad idea (different internal resistance, chemestry ...). when the pack died, i ordered some cheap replacement from ebay just to keep me going. this of course is no zippy. it's this one:

1946,lipoT7MOE.jpg


which is btw not the ideal replacement of the different dimensions (which i recongnized after ordering :()

so may i put them in serie with the zippys and then in parallel with a second pack of zippys? or shouldn't i do that?
 
ok. now i swallowed the bitter pill, and ordered an overpriced ZIPPY Flightmax 5000mAh 4S1P 25C to repair my 6s pack (and probably any other pack i have that may have a damaged cell in the future).

BUT: how do i securely seperate the packs from each other. the are glued together. will i damage the insulation if i carefully just pull them apart? or is there some special trick to do it? desoldering the pack was no problem at all (using a 80w soldering station and desoldering wick)
 
Separating can be done with a bit of warmth, a solvent (isopropyl alcohol may work; if not denatured alcohol probably will but test on teh plastics first as it dissolves more than a few), and a plastic card like a credit card or similar, to ease down between the cells.

There are some threads about doing this.
 
The worst thing that will happen is the cheap pack will get a hammering, compared to the packs with less resistance. It will sag, and the pack that is paralelled to it will get discharged a bit harder than the others. It won't kill it, unless you overdischarge it.
 
update: received my 4s pack today. dismanteled it, pried the cells apart and exchanged the dead one with a new one. all went right. but now it takes ages to balance those 0.4v cell mismatch :(
new cell is 387mv higher. discharge of the single cell to match the other five is 5mv/4min. that's 5h+ !!

but after all it was much easier than expected and soldering noe looks better than before. pack will be put in a new heatshrink tube and look like new :)
thanks guys!
 
after the first test run for 25km in the city, going 45kmh+ several times, with a lot of stop and go, i immediately switched the bike of when the low voltage "alarm" kicked in. all batteries are quite warm. not too hot to touch, but really warm. as a laptop sitting on your lap. so i guess between 40-45°C.

i immeditely stopped the bike, and took a look at the all-time connected cell voll meter. one of cells was showing 2.65v. i thought d*mn. i didn't double check, but i'm quite sure. not back at the office i did measure all cells:

Code: 
3.35 3.27 3.37 3.40 3.36 3.38 = 20.2
2.99 3.14 3.19 3.32 3.07 3.39 = 19.1
3.24 3.12 3.40 3.44 3.17 3.39 = 19.8
3.42 3.51 3.53 3.42 3.42 3.59 = 20.9 <- the third or forth cell of that pack did show 2.65v

i read a lot of you guys charging with power supplies, only needing to balance every 20-30 charges. i have a delta of 0.4v after one discharge. and a delta between the lowest and highest pack of 1.8v. is this ok?
and the second question: how can it be that the voltage came back after some time? i know that there is some sag under load, but this phaenomenum is new to me.
 
izeman said:
i ignored (or missinterpretated) the low voltage alarm and ended up with one "dead" cell in one of my 6s zippy packs.
i connected the pack to several chargers, and all of them showed 5s packs. then i tried to charge them (0.1A only) to see what happens. of course the pack was put in a lipo safety bag.
this if what the chargers show. one cell down to 0.00v ??? and one missing:

1933,zerovoltWV6OO.jpg


anyway to revive that pack?

ps. there was no physical damage done to the pack.
Click to expand...
had same problen it turned out to be broken conecter board thay dident put enouf solder on it and it shorted quickly and caused the trace to blow out on the board above the battery check it out its a simple fix but if its a low voltage sell u can do what i did i used a 3.3v power supply that out puts 0.3 amps it takes a bit but it will revive it just dont go nuts with amps or u will build gass in the cells iv done it lots of times as long as its not totaly dead its revivable then after that do a cell test on it charge it then disscharge it and check resistence and capacity and make ur choice from there just watch the cells and the cell temp as u charge
 
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