Mr Mike
16 years ago
They are NiMH, just a replacement for their older NiCAD packs as these are being phased out - bad metals and all, in them...
Mr Mike www.mineexplorer.org.uk
royfellows
16 years ago
Morning all

I have just been lying in bed thinking about the 2 video clips on utube to which Miles was so kind as to provide links.

I recon I have the pyrotechnic display in the first clip sussed. What they have done is to connect the Li Ion to a 12 volt car battery, if you think about it; it goes with the location, an underground car park.

Obviously, a car battery is capable of delivering a lot of power with no current restriction, shorting one is how cars are set on fire. Obviously a power supply such as would form part of a proper charging arrangement could not deliver this kind of power.

From Wikepedia:

Lithium-ion batteries can rupture, ignite, or explode when exposed to high temperature environments e.g. in an area that is prone to prolonged direct sunlight. Short-circuiting a Li-ion battery can cause it to ignite or explode and any attempt to open or modify the casing or circuitry is dangerous. For this reason they normally contain safety devices that protect the cells from abuse.

It appears that it’s the heat that causes the problem. As I have remarked elsewhere, overcharging Ni MH causes them to swell and therefore become useless in most devices. I have little doubt that leaving on charge indefinitely would cause the case to rupture.

My avatar is a poor likeness.
derrickman
16 years ago
re our burst cell, it was connected to a 12v supply; but a low-power, fused one - a trickle charger - hence ( presumably ) we didn't get the fireworks, although we did get some 'fizzing' from the first stage of the split casing.

field electronic equipment would normally be stored out of the direct sunlight, this was in West Africa so the sun there has to be taken seriously


''the stopes soared beyond the range of our caplamps' - David Bick...... How times change .... oh, I don't know, I've still got a lamp like that.
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