LiPo, LiFe, Li-On conversion?

[Mario]

Capacitors can just fail. They only work so many times. :P

Lithium batteries don't "spontaneously" explode. There's a certain set of conditions that have to be met, all of which have to do with abusing the battery and pushing past its limits.

If you overheat, overcharge, undercharge, short, or puncture lithium cells, they can catch fire and/or explode. Most of the laptop recalls you've seen are because of bad product design, where they let the batteries get too hot, by placing them too close to a heatsink or something.
Or, batches of batteries can be bad because of defects in manufacturing. There are a couple cases of that.

But they don't randomly explode. I've been working with them for years in mobile hardware projects and I've never had any safety issues. And the rest of the world has been using them for several years in mobile and other applications. They're used in pacemakers and hearing aids, for goodness' sake. What makes you think they're not safe under normal conditions?

[Varak]

Was talking to a friend over Christmas who is seriously into the radio-control scene. He's owned a hobby store for over 30 years.

He said that they are building race cars whose battery packs can sustain 400+ AMP discharges. Not sure about how many cycles at the rate, though.

In talking to him about battery technology, I found he uses the same conceptual idea of matching discharge curves in putting together packs that we use in rebuilding ours.

Am wondering if I should put him in touch with the battery experts here to see what input he might be able to give. I'm pretty sure he uses Lipo batteries.

[theaveng]

I posted images of my insights when I bought them (blue from ebay, and silver from Craig's list). But both listings are now deleted and the pictures gone.

re: Safety of Lithium. As I said before, we can't know for sure if these "new chemistries" are safe. They could have no problems whatsoever for the next 10 years (thus proving they are safe), or we could open a newspaper and read about one spontaneously combusting (showing they are no safer than the old chemistry).

Well it's happened: The FAA has grounded ALL Boeing Dreamliner planes because their lithium-ion batteries are catching fire. And that plane has billions of engineering & research in it. Also frequent audits by FAA inspectors to ensure a safe design. There is no way I will put one of these batteries in my lowcost car which does not have that level of engineering detail or scrutiny behind it.

IMHO

[Cobb]

Maybe lithium batteries and air craft regardless of size shouldnt be mixed?

I remember back in the day of air cooled cars that if some were in a fire you couldnt use water to put it out as they had magnasium in the crank cases.

Originally Posted by theaveng

Well it's happened: The FAA has grounded ALL Boeing Dreamliner planes because their lithium-ion batteries are catching fire.

[biododge1]

[QUOTE=Cobb;

I remember back in the day of air cooled cars that if some were in a fire you couldnt use water to put it out as they had magnasium in the crank cases. [/QUOTE]


so im to presume this would apply to our cars as well because of the oil pan? (or, is that not enough magnesium to be a concern?)

[Cobb]

I wouldnt really worry unless it was on a dyno. Then, dont use water, but an ABC approved extinguisher. You would want to treat it like a grease fire and smother it.

[jonnyvtec]

Boeing's problem is they went for the energy density option which is colbalt like the Tesla Roadster.


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[Cobb]

So there is a method to the madness? You just cant half hazardly wire them up, toss them in a box full of wood shavings and petroleum distillates and hope for the best?


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[roflwaffle]

Pretty much. There's a video of someone shooting an LFP cell with a revolver and shorting another with the end result being a lot of smoke. Otoh, people will also turn LiPo batteries into small flamethrowers with some generous overcharging.

Edit- Just to spell it out, I'm fairly sure there's a huge difference in Li batteries with different chemistry because some have very high internal resistance and will not vent hydrogen under any circumstance, while others will vent hydrogen and have low internal resistance.