battery fires

[Tony Smith 7]

Posted by Peter Beeney on 02/12/2010 19:35:04:

   Later there was a similar happening to some laptops, at a laptop show in Japan. There was very little info on this, that I could find anyway, but the was a lot of suspicion that this was also down to counterfeit batteries.

   I think this is probably a massive problem, it appears that there are good ol’ genuine fakes of just about anything in today’s world.

   PB

                                                                              

 

 That was Dell, but I don't remember any reference to suspected counterfeit batteries.  See BBC Article on the recall.    And this demo ..  Fixed Youtube link

 

Edited By Tony Smith 7 on 03/12/2010 08:41:40

[Chris Bott - Moderator]

Tony that youtube link goes to a cisco config guide.. Not sure that's what you intended?

[Tony Smith 7]

Cheers, fixed now I think ...

[Ultymate]

Peter Beeney writes that "lead acid batteries give off Hydrogen when under heavy discharge", sorry to say Peter it's when they're either being charged or have just come off charge therefore when jump starting cars it's the donor vehicle's battery that is likely to explode should any sparks be generated near it's battery  As for laptops and mobile phones I believe they now have a safety circuit built into them to prevent overcharge and the subsequent fire

P.S as an aside here when jump starting safest way is to connect pos to pos first assuming negative earth and then connect the neg side making the final connection not direct to the battery but either direct to a metal part of the engine or chassis away from the battery, this being the professional H&S/PC way of doing it  

Edited By Ultymate on 03/12/2010 08:47:10

Edited By Ultymate on 03/12/2010 08:52:34

[Steve W-O]

Posted by Ultymate on 03/12/2010 08:45:43:

 

P.S as an aside here when jump starting safest way is to connect pos to pos first assuming negative earth and then connect the neg side making the final connection not direct to the battery but either direct to a metal part of the engine or chassis away from the battery, this being the professional H&S/PC way of doing it  

Edited By Ultymate on 03/12/2010 08:47:10

Edited By Ultymate on 03/12/2010 08:52:34

 

 

It makes a lot of sense from an electrical point of view, aside from safety, especially to connect to the engine on the car that is being started.

[Erfolg]

Mention has been made of an overcharge protection circuit in the batteries as fitted to computers and mobile phones. I understand that these are essentially Lipo chemistry in a hard case, using different anode and cathode materials.

 

I would have thought that our Lipo chargers would have this type of circuit built into them, rather than the battery. There is in principal no amount of space available in a charger, rather than the confined volume of a hard cased battery.

[Chris Bott - Moderator]

In Laptops the protection is generally built into the overall plastic case that the batteries are built in to. This is specialist and is designed completely around one particular battery size and chemistry.

 

With us, we demand a charger that we can change settings on to suit different needs. And here is most of the issue, operator error. I have done it, and seen the consequences. It doesn't take much of a slip up. 

 

I have one charger that is LiPo only and only has a connector for the balance lead. it is almost impossible to set this one up incorrectly. Others do their very best to check your settings for you but they can be fooled.

 

I charged a 3S LiPo on a 4S LiFe setting. The voltages were checked by the charger and were in spec for the settings I chose. Later though, the voltage got too high and a fire ensued. I was in attendance and all was made safe.

But there you go, I believe I'm pretty careful. But I got that one wrong. 

[Erfolg]

Chris

 

My charger which I assume is very ordinary, does check something after you press the start charge button. If anything is not to its liking, it gets upset, with a flashing LED screen and a intermittent buzzer sound. It does not start until satisfied. Even when charging, it can get upset, if say you move it.

 

I am assuming that this is a protection system of some sort.

 

I would think, perhaps wrongly that 95% of electric modellers have something similar.

[Chris Bott - Moderator]

Yep that is very likely the charger checking that everything it can sense is the same as you programmed.

 

I just found a combination that fooled it, and it made a fool of me too.

[Peter Beeney]

   It was in an electronics magazine that I read about the suspect counterfeit laptop batteries, and that might well have been all supposition anyway. I think there was subsequently a mass battery recall, because of contamination with some sort of metal dust, as I remember? Even then, that appeared to be a bit of a knee-jerk reaction, because some manufactures that decided not to recall were vindicated when eventually it transpired there wasn’t going to be widespread problems.
   I remember seeing a photo of the actual laptop going on fire, at the convention. With hindsight, was this more than a slight coincidence, in full view with all the Japanese delegates standing around watching? Why did it choose that exact moment to pop? Why don’t they explode out in the suburbs, as well? Or perhaps they do, and it just doesn’t get reported.
   I’ve not researched any of this at all, maybe I need to go back and have another look.

   Ulty, With the greatest respect, what I actually said was: a battery under heavy discharge can generate hydrogen gas in sufficient enough quantities to cause an explosion. You only need a teaspoonful in the top of the cell. I remember watching two blokes trying to jump start an oldish large car, and it was the flat battery on the stricken vehicle that they blew one end cell off! Anyway, whatever, either battery zapped, it’s not good news. I would certainly agree that lead-acids do produce much more gas when charging.

   I think lithium batteries have always had these built in protection devices, that’s what I was trying to say. Fully automatic charging/discharging. It’s only when batteries were produced without these devices that aeromodellers (and perhaps many other different branches of industry now) were able to take advantage of this. But it also removes an element of safety. We can now tinker! So the question might still remain, is it the chemistry of the lithium cell that is causing the occasional problem, or is just operator error? Or perhaps an element of both?

   Just to supplement your very sound jump-lead advice, if I may, I would personally consider the most dangerous time to be is when disconnecting the jump leads, this most likely to cause sparks. So I’d switch off the engine of the donor vehicle first, if it’s running, then there’s least chance of any load. Then I would disconnect the negative lead first, from the metal work on the engine, both ends, to stop the loose end splashing around, that’s been done before, very spectacularly, and then the pos lead last. I’m not sure if this is H&S, or even PC, it’s just my way of trying to avoid a bang, to say nothing of the expense!

   We have to use jump-leads at the field on the odd occasion. Sometime the capacity of the modern car battery seems to be not that great, when it has to provide the watts for that last extra powered glider flight. We’ve long had a little unwritten rule that no one is left alone, or at least, without the engine running. I’m sure that must be quite commonplace, too.

   PB