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Conundrum

Sun Aug 30 2015, 08:10AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

having had a lead acid that caused my entire car to fail while driving, i can see this being very popular.

-A

hen918

Sun Aug 30 2015, 11:42AM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Conundrum wrote ...

having had a lead acid that caused my entire car to fail while driving...

-A

How on earth did your battery do that? Internal short?

EDIT: after looking at the link, I would suggest that these batteries could cause more problems than they solve. If the electronics fail, lots of nasty things could happen.
I Have 8 of the LiFePO4 cells pictured in the link and 4 of them have died due to the balancing / protection circuitry failing and slowly discharging the cells to 0v

Conundrum

Sun Aug 30 2015, 02:49PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

hen918 wrote ...

Conundrum wrote ...

having had a lead acid that caused my entire car to fail while driving...

-A

How on earth did your battery do that? Internal short?

To replier: Yeah, that did it. BIG blister on the back of the affected cell close to the clamp, fortunately it didn't melt through the case.

EDIT: after looking at the link, I would suggest that these batteries could cause more problems than they solve. If the electronics fail, lots of nasty things could happen.
I Have 8 of the LiFePO4 cells pictured in the link and 4 of them have died due to the balancing / protection circuitry failing and slowly discharging the cells to 0v

Yeah, same experiences here. (cheap controller, nuff said).
More e-bike packs fail due to the $9 controller failing in creative ways than from bad cells.

I think however that given the good track record of LiFePO4 the chances of a fire caused by these are lower than even from a lead acid.
Not many car batteries include internal fuses and overheat/etc protection.

I do think they should add warnings about not jump starting other vehicles except using safe procedure as the load from doing so might be too much.

Also to OP: do you still have them?
I've managed to recover 80% of my "totally deader than dead" LiFePO4 from DX, with a few clever tricks: for those curious PM me.

Only one permanently failed and that was due to an external SNAFU which made the cell bulge up and the failsafe tearaway correctly opened isolating the cell in that case.

Four of mine were overdischarged twice (never learn!!) and recovery procedure did the trick although they didn't work particularly well probably due to copper shunts.
With low capacity cells procedures that would be incredibly dangerous on 3.3Ah screamers (tm) seem to work although there is always a capacity penalty.
Such cells with care still have value for solar power apps if buried in dry sand well away from anything flammable just in case.

Also worth noting, I have unpatented procedures for scanning of "bad" cells of differing types that can identify which are likely to come back and which should be disposed of safely.
Typically about 60% of "bad" cells fall into the recoverable category but if they have dwelled at below 0.9V (LiFePO4) or 1.3V (LiNiMnX) if >1.5 Ah they are totally unrecoverable.

Also see

(note about runaway cells!)

Enceladus

Mon Feb 13 2017, 06:40PM

Registered Member #61428 Joined: Sat Jan 14 2017, 12:39PM
Location:
Posts: 50

There's not really any *new* battery technology in there per say, and it's not even the first supercap to be designed to replace conventional lead acid batteries, but it is definitely a pretty common-sensical development. It's too bad car designers couldn't have had the foresight to simply integrate features like this to begin with.

I'm all for supercaps though. I've been wanting to see them and lithium ion capacitors begin to see some more widespread use.

There's been some interesting development into employing flywheel energy storage for regenerative braking in cars while also making use of the gyroscopic effects to enhance handling and stability.

Most of all I'm looking forward to seeing compact fuel cells and lithium air batteries. And of course, all the impossibly amazing things they keep promising to do with fullerenes, nanotubes and graphene. Still waiting on that elevator to space.. and.. cybernetic implants. If I only had a positronic brain...

Conundrum

Tue Feb 14 2017, 05:53AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Its interesting to note that NiMH are *STILL* used in space because their failure modes are well understood and can be accounted for in software.
I did find out that old NiCads if precautions are taken such as carefully reinforcing the rather inefficient cardboard insulator eg with silicone but leaving a vent gap increases their lifetime manyfold. 10 years and counting!!

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