dead cell in an almost new Turnigy 5Ah 6s

[dakh]

If it's any consolation, I'll take the 6s 5ah packs from you in Seattle if they are free...

Oh come on that 6s is worth at least a 6p[ack] of some good crafts brew The bum 5s leftover. .. maybe a pbr.

 

[dakh]

5Ah, 4S hardcase bricks work much better for me than 5S, 6S configurations. $25-$28 shipped USA is much easier replacement pill to swallow than higher cell counts in the event of a dud. Plus the fact 4S produced/sold in very high volume possibly insures the freshest stock available?

Maybe I’ve been lucky or maybe my “system”, BMS and learned knowledge have been working well enough to not suffer any premature failures in over 40qty 4S bricks spanning nearly 3 years.

3years prior that, I’d used naked 5S, 6S unprotected bricks like the OP. Many more problems, some of which I created and some of which were just par for that course.

I would love to get into some of those Tesla cells. Just need to make up mind about what configuration to weld up but sooner or later I’ll try that path. For now, moderate size 4S hardcase BMS protected RC Lipo serves me very well.

btw, I generally do not run very large capacity packs. My mini motor bikes do great on 16S1P (300Wh) and my larger 2kW stuff is happy with 16S2P (600Wh). Anything more than that becomes very difficult to wire up and safely maintain, IMO.

As far as charging and storage, BBQ grills can be your friend….

Thank you, I like the 4s idea, would do that if i had to start over on lipos. As far as pack capacity, personally i went for 14s5p on the tesla build because i do want to have an option to get reasonably good current out of these without stressing out the pack or having to deal with heat issues. Plus these things are so light i didnt see a good reason to compromise on range -- other than money of course.

 

[dakh]

Thermal runaway can be achieved if the cell has some amount of charge, and the cell is impacted on the positive terminal compromising the crimped gasket between the positive and negative, thus shorting out the cell.

What are the actual consequences? My understanding is if one cell has run away a lot will depend on how the pack is built, might be it or might be chain reaction and fire. That's where tesla invested a lot and used all sorts of tricks to make the latter nearly impossible.

I might just kill a few cells to find out for myself. Or ask tesla guys

 

[Hillhater]

i never said that.

you are the asshole for making up words i never said.

i don't even understand why you did that either except you people seem to think you can insult me because the insiders who run this place think it is so funny because i told them they should all quit for allowing these abuses of me and the few women who ever come here to be insulted and abused for free with no consequences.

Keep your hair on dnmun. No need for a rant.
It's obvious that was just a "cut/paste" error in a quote, by Austin P

 

[RVD]

i have purchased around 20-30 6s 5ah turnigy lipos and around 10 4s 5ah hardpacks turnigy lipos over the years and i have been lucky...never had a bad cell AFAIK.

i take good care of my lipos though. i charge up to 4.05 and don't let them go below 3.7.

i don't use a BMS but i monitor closely with my CA and i know my bikes, etc.

also, i don't know if this is a good thing or not but i use linoleum squares and gorilla tape to make my soft lipos into hardpack lipo packs once i build battery packs. many years ago, doctorbass had a theory that if you can try to prevent cells from puffing, it helps prevent them from going bad...it was controversial at the time (and still probably is) since puffing is also an early warning sign that a cell is going bad so might not be a good thing to prevent it but i have been doing that for about 3 years and haven't had a cell go bad on me (thread link: http://endless-sphere.com/forums/viewtopic.php?f=14&t=45946&p=719110#p719110)

 

[RVD]

If it's any consolation, I'll take the 6s 5ah packs from you in Seattle if they are free...

Oh come on that 6s is worth at least a 6p[ack] of some good crafts brew The bum 5s leftover. .. maybe a pbr.

lol, you're probably right. i don't need any more lipos though...still have a big stack from various sales over the years.

good luck with the build. my builds are nowhere near as ambitious as yours...i get scared on my bike if i hit 40 mph.

i think with lipos in general and messing with them, it reminds me of a sign i read in a hardware store along the lines of:
if you buy from us brand new, we'll install it for free
if you bought from us brand new and did 1/2 of the installation yourself and want us to finish the rest, we'll install it for $10

 

[dakh]

lol, you're probably right. i don't need any more lipos though...still have a big stack from various sales over the years.

good luck with the build. my builds are nowhere near as ambitious as yours...i get scared on my bike if i hit 40 mph.

i think with lipos in general and messing with them, it reminds me of a sign i read in a hardware store along the lines of:
if you buy from us brand new, we'll install it for free
if you bought from us brand new and did 1/2 of the installation yourself and want us to finish the rest, we'll install it for $10

I got no ambition other than a reliable, lightweight commuter. 40mph? I know what road rash is, all too well. If I wanted to go fast I'd just ride one of my motorcycles So yea, keeping it simple for now.

I'm harboring thoughts to build something that I can go race indoor flat track in 150 and under CC class. Maybe a BMX or make an electric bike out of XR80 frame or some such.

 

[RVD]

If it's any consolation, I'll take the 6s 5ah packs from you in Seattle if they are free...

Oh come on that 6s is worth at least a 6p[ack] of some good crafts brew The bum 5s leftover. .. maybe a pbr.

Interestingly enough, I have a 6s pack that is slightly starting to puff (the plastic turnigy wrapping is still fully entact though) and I'm guessing that I have a bad cell. Anyone in the Seattle area want it for free?

Otherwise, it's going into a discharge + salt bath before disposal later this weekend probably (if I get around to it).

RVD.

 

[sharkmobil]

I've had the same issue (a cell puffed after first cycle). Anybody knows some interesting recipes that involves that lithium goop?

 

[RVD]

i could always do a fun experiment in my back yard...i guess it would be my own version of hooking it up to a charger and letting it charge above 4.2v and see when it blows up (if ever).

of i can just get impatient and drive a nail through it to short it out.

 

[dakh]

i could always do a fun experiment in my back yard...i guess it would be my own version of hooking it up to a charger and letting it charge above 4.2v and see when it blows up (if ever).

of i can just get impatient and drive a nail through it to short it out.

If it's at 0 volts shorting it won't do much. If I had a junk charger I'd do #1 but don't want to risk a good one

 

[RVD]

i have a bunch of chargers. but there's no guarantee that the charger will be ruined...maybe just the charging cable. i guess i could charge it all up and then just short the leads but i think my leads would actually just spark and break off (using andersons).

i actually don't know what the charge is that. i was working with all of my batteries a few nights ago and saw this puffed one and just took it outside immediately and left it there all week.

 

[dnmun]

the one experiment you could do but would not is to charge up the lipo pouch that discharged to .7V to full charge and then measure the self discharge rate with respect to the others in the pack. we could learn something from that but we don't learn anything with this stuff.

 

[RVD]

the one experiment you could do but would not is to charge up the lipo pouch that discharged to .7V to full charge and then measure the self discharge rate with respect to the others in the pack. we could learn something from that but we don't learn anything with this stuff.

ok i'll do that this weekend if i have time. that's the 4s pack that i'm not giving away because i want to try that test...

 

[dnmun]

this is the only lipo pouch we have seen self discharge to such a low voltage over a long period of time.

in the case of lipo pouches which self discharge rapidly to low voltages we can assume the short is significant.

if this pouch has very low self discharge rates in comparison to the others then it would be worth evaluating the internal resistance of it with respect to the others in the pack.

that is why that pouch is useful, to learn if going to low voltage causes some damage other than the problem that led to high rates of self discharge we have seen in other pouches.

it will not explode if you use a balancing charger, but you gotta bring the voltage of that low cell up to the same as the others first before charging.

if you have other pouches which are puffed and you wanna discharge them then you can use that puffed pouch to charge up the low voltage pouch by connecting it in parallel through a resistor to limit current. when it gets up in voltage then the balancing charger will charge it.

you can balance the others to it by using a light bulb or big power resistor and drain charge off the others in the pack to pull them down to the level of the low pouch as it is charging up.

 

[RVD]

dnmun, would it be too dangerous for me to just send you the 4s pack so you can do whatever testing you want with it? i think it might be a bit beyond my skills to mess with it. well, i might get there at some point but the batteries are stored outside as of now and might deteriorate faster than when they were dangerously stored in a box in my garage.

the 4s pack seems slightly puffed now but the 1 cell is still at 0.7v. this 4s pack has not been charged ever (since purchase 3 years ago). the other cells are still in the 3.8X volt range to be expected when shipped.

i did test all packs when i received them so this one was fine when received. as stated earlier in this thread, i haven't had a bad cell with lipos but when i finally took out this box and started evaluating each battery in detail one by one, this is the first. the 6s doesn't actually have any bad cells from initial analysis (although not IR analysis) but is puffed so i'm just discarding it to play it safe.

RVD.

 

[dnmun]

no, don't mail it. you can fix the puffing by putting the pouches into compression for awhile. .

the one at .7V has discharged slowly so if you can charge it up and then watch the self discharge rate with comparison to the others then it will give us information about how low the lipo can go in storage and be recovered.

if you don't push current through it while in this over discharged state it should not have any problems. as soon as you apply even a few mAh of charge the voltage will climb to 2.8V and then it will charge up at the normal rate.

i doubt if it will actually show much difference from the others but it would be good to confirm it.