LiPo bank failure- What Happened?

[harlan]

Expensive lesson but could have been worse. Careful with those LiPos. I'm sure Mrs. Dillard wouldn't be too pleased if you burned the house down.

[teddillard]

Update. The bike has been sitting while I've been doing the work on the new tank. All the banks read around 3.95V per cell, and I took it for a spin on Sunday. The cells were reading around 3.75 or so when I got back in, on the banks I had the cell loggers on (still waiting on connectors, so they weren't on all the banks).

Got back and started topping them up... and got another error message on one bank. The #1 cells on one bank were all reading 0. (Three individual packs.)

Figure these were just packs that got weakened by my previous mistake, and it took a while for them to fail... but I'm still amazed that all three fail like that. It sucks. I think I'm going to start doing what Kyle suggested, and taking a few apart to see what the hell is going on.

booooooo.

[jonescg]

I know it's super convenient to buy the 6s packs from HK and parallel all of the balance taps, but as you've worked out, if one cell fails, it drags 6 down. If they were paralleled at the individual level, you would have one 'cell' of p individual cells you can ditch, but opening up all of the 6s packs to remove each one individually will be a pest.

I've been soldering individual cells together and the results have been great; much better use of space too. If you want to try some of the 4p or 5p boards I've got, just let me know.
Cheers mate,
Chris

[teddillard]

I know it's super convenient to buy the 6s packs from HK and parallel all of the balance taps, but as you've worked out, if one cell fails, it drags 6 down. If they were paralleled at the individual level, you would have one 'cell' of p individual cells you can ditch, but opening up all of the 6s packs to remove each one individually will be a pest.

I've been soldering individual cells together and the results have been great; much better use of space too. If you want to try some of the 4p or 5p boards I've got, just let me know.
Cheers mate,
Chris

Cool! No, I'm running the 4S hardcase packs, no the 6S, but yeah... I'm definitely thinking about what my options are. Do you have a photo of those boards?

[jonescg]

Cool! No, I'm running the 4S hardcase packs, no the 6S, but yeah... I'm definitely thinking about what my options are. Do you have a photo of those boards?

You can read the thread over at ES http://endless-sphere.com/forums/vie...p?f=31&t=38252

The first pack was a 3p 10s pack prototype, but now I have PCBs made up with holes for balance taps ideal for Method's boards and/or balance taps to the serial plug of your choice. I have 3p,10s boards, 4p,7s boards and 5p,6s boards. They are designed with the 5 Ah 40C Turnigy cells in mind. The boards can be cut up and rejigged to suit your specific shapes, but overall they are pretty versatile. I have dragged 150 amps through 8 ga cables on the 10s pack and the cells barely roll over in their sleep. I built Roney a 24s 15 Ah ~90 volt pack in a day and an afternoon.

Since it would be cheaper for you to order the cells in the US, I can send the boards and tinned copper; much cheaper this way.

[teddillard]

huh. Well, this morning I borrowed my buddy's badass super-powerful soldering iron, pried the cases apart and played around unsoldering the cells. Here's the post showing how I did it: http://evmc2.wordpress.com/2012/07/0...dcase-4s-pack/

They come apart OK, basically just heating up the solder and flinging the puddle off the board, but, when I sat down in earnest to piece good cells together to make some "new" packs, I found that more cells had failed. They've just been sitting at around 3.5V, and instead of only one cell in each pack needing replacement, it was more like only one cell was still showing voltage in each pack.

I'm beginning to accept the cold, hard truth of the matter... what Luke said early on. The whole pack is pretty much toast. Those packs are not even worth trying to salvage, and I had another bank fail for no good reason (other than my first mistake), so I'm back to the drawing board, and planning a new pack.

Foolish though it may sound, I'm thinking of a bigger pack of the hardcase Turnigys. But this time I know to be more careful about doing stupid stuff like leaving the bike turned on...

[Athlon]

If you are interested there is a Group buy on 20Ah A123 cells http://priuschat.com/threads/is-ther....110235/page-2

right now price for A123 20Ah puoch cell is about on par with TS cell of same size

[teddillard]

If you are interested there is a Group buy on 20Ah A123 cells http://priuschat.com/threads/is-ther....110235/page-2

right now price for A123 20Ah puoch cell is about on par with TS cell of same size

Not so much. The Turnigy 5000mAh 4S1P 14.8v 20C hardcase pack is selling for $23.65 at HobbyKing. Unless my math is failing me, that's still a better price.

[Allen_okc]

most cases the hobby king cells have been awesome, so lesson learned you should be able to create a new pack that will serve you better this time...

personally i have never had a good outcome with trying to salvage a battery pack...