Have any Lithium-Polymer batteries made their way into headlamps etc. yet?

There seem to be a lot of advantages in terms of power capacity compared to weight, but this is slightly negated by the inherent instability of the battery itself, although to be fair this generally only manifests itself when charging* - albeit some advice I've seen is that if you damage one, best not put in in a vehicle or house for a couple of hours... 😮

* This http://video.google.com/videoplay?docid=3690260570423705609  demonstrates the problem - 33 seconds in.

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Have any Lithium-Polymer batteries made their way into headlamps etc. yet?

After watching that video... I hope not... Certainly not into a headlamp anywhere near my head anyway :lol:

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I suppose it's telling that you can buy a protective case for charging - http://www.batterystation.com/lithiumpolymer-liposack.htm  - although I'd probably prefer a lead box!

This video is worse than the one linked to above: http://www.batterystation.com/LipoSackv.wmv 

All the same, given that the problem occurs when charging, they should be relatively safe in actual use... ::)

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I gather interesting things can also happen if you distort their casings.

I would imagine that you can also have interesting fun if you use the puncture/water combo.

:)

What worries me is that you need the proper charger to be safe, but is the charging circuit properly fail-safe so that it shuts down, always, if it itself is faulty, instead of applying too much voltage?

I know how to design such circuits, but they don't come cheap, in comparison to what is normally used.

But charging in a strong, fireproof container, may be one way round the main problem. There is still the problem of damage while in use, and something sufficiently strong to contain the possible explosion may make the thing heavier than the traditional lead acid battery.

You just don't get something for nothing. On the other hand, my toy helicopters rely on these batteries, but I charge them at a safe distance, even though the charger purports to be safe.

I wonder if a http://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery  lithium iron phosphate battery, which does not explode, might be adequate for mine exploration?

Having that battery on your head is similar to riding an old steam powered motorcycle with the boiler down between your legs. The risk is very similar.

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Li-Po Batteries have the annoying habit of having large thin sizes, for example a 7.4V 5.4Ahr is 148mm x 52mm x 13mm. With a box prob only suitable for belt mounting.

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What worries me is that you need the proper charger to be safe, but is the charging circuit properly fail-safe so that it shuts down, always, if it itself is faulty, instead of applying too much voltage?

I know how to design such circuits, but they don't come cheap, in comparison to what is normally used.

In my experience, a Li-Po battery will come with a built in over-current protection circuit and an over-discharge protection circuit. This is within the battery pack, so you're often not aware it's even there (unless you poke about and find the tiny PCB).
Additionally, there is often a temperature sensor to ensure that the battery doesn't overheat, which is connected to the charge controller IC.

Quite what the issue is with these incendiary laptop batteries, I don't know, but I would use a Li-Po battery as long as it was suitably armoured.

Chris.

Quite what the issue is with these incendiary laptop batteries, I don't know, but I would use a Li-Po battery as long as it was suitably armoured.

Chris.

The flammable laptop battery problem is due to a (large) batch of batteries made for Sony but also sold on to
other manufacturers like Dell for example that contained metal particles that can lead to shorting, overheating & fire. Oops

EDIT
Besides the batteries in question are Lithium Ion rather than Li-Po. Li-ion has different characteristics. Less capacity for size than Li-Po but more stable and it dosn't suffer from 'memory problems' like the old NiCad batteries.

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The information re batteries is contained in this http://en.wikipedia.org/wiki/Rechargeable_batteries  link from Wikipeadia.

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I've been using Li-po batteries for sometime now. The issues concerning their use and charging are somewhat subject to more than a little hype. Misuse of any battery or energy storage device (capacitors for example) can lead to dangerous situations.

Because these batteries have little or no internal resistance they can hold and discharge vast amounts of energy for their size. They should not be discharged completely or over charged. To do so will ruin the battery in the first case and likely to cause as shown by Vanoord a fire in the second. By the same token if the battery is damaged in say a crash or the structure is pierced then there could well be a short created and the battery will eventually catch fire.

Using a dedicated charger and never leaving the batteries on charge without supervision, I've never had any issues. I shall be using them on the ROV as they can not be matched for size/capacity. I see no problem if the battery is well protected and a discharge limiting device is fitted and they are charged in accordance with the manufacturers recommendations.

If you do use a mutli cell/voltage dedicated Li-Po specific charger, then always make sure you select the correct voltage and cell value before turning the charger on. Dead short on the terminals is also a no-no. 😮