At 10pm one night, a battery inside David Carr-Smith's transistor radio exploded – filling the air with acrid black smoke.
The explosion was powerful enough to send the radio flying off the nightstand and on to the bed. Embers splattered the walls and floor, close to the cot where David's baby son was sleeping.
David smothered the radio with a wet towel and removed a smouldering battery from the bed. The damage was contained but both the nightstand and duvet were left with obvious scorch marks. David says he dreads to think what could have happened if he hadn't been in the bedroom at the time.
The battery responsible for the damage looks likely to have been a disposable AA lithium battery. The black residue from the explosion tested positive for lithium.
Lithium batteries have a reputation for being long-lasting. But the downside is that they contain metallic lithium, which is extremely flammable, and they’re known to be capable of exploding from overheating. The Civil Aviation Authority requires portable electronic devices containing lithium batteries to be put in carry-on luggage and not placed in the hold.
The actual amount of metallic lithium in a single AA battery is typically very small. But there's a risk that when the battery burns it’ll spray molten lithium and spread the fire.
A compounding factor in this case was that the lithium battery in the radio was mixed with another type of battery. Mixing batteries is potentially dangerous.
Safety advice
If you're using disposable batteries:
- Don't mix types, brands, or ages.
- Don't expose them to high heat or get them wet.
- Don't try to recharge a disposable battery.
- Remove batteries if the device is also powered by household mains power or if it's to be left unattended for long periods.
- Dispose of a battery that feels hot, changes colour or shape, or emits an odour.
- Consider switching to rechargeable batteries. They're cheaper in the long run, perform well, and you're not constantly throwing away disposables.
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We just brought some Panasonic evolta rechargable batteires. they hold their charge for a long time when not in use. Found them very good so far.
Hi Dugald and JonB,
We have been testing rechargeable NiMH batteries, which will be published shortly.
The latest NiMH batteries, including the ready-to-use type perform far better than the previous generation of NiCad rechargeables, which suffered from lower capacity and a memory-effect. All rechargeables lose more charge than disposables when stored though, so they need charging just before use to get the best from them.
The cost of the batteries and charger is a lot more at the start, but our experience with NiMH rechargeables is that this extra cost can be usually be reclaimed in fewer than a dozen recharging cycles.
New alkaline cells deliver 1.5 volts and charged up rechargeables give 1.2 volts because of their different battery chemistry. However, the discharge curve of a NiMH rechargeable cell is quite flat - they stay close to 1.2 volts for most of their discharge cycle, before falling below a volt quickly at the end.
In use, the voltage of a typical alkaline disposable cell drops quickly from 1.5 volts to around 1.3 volts, and then continues to reduce linearly to less than a volt at the end of its useful life. While the NiMH cell starts off at a lower voltage, the alkaline disposable very soon falls to the same level, then continues to fall below the voltage of the rechargeable for the remainder of its life.
There shouldn't be a problem running the majority of devices on rechargeable NiMH batteries. However, you may find conventional torches aren't as bright as they would be with fresh disposable batteries, (LED ones don’t seem to suffer) and battery life indicators might give false readings (they rely on a linear reduction in voltage that you get with alkaline disposables).
Regards,
Paul Smith
Technical Writer
We use rechargeable batteries for the last 6-8 years and we never had any issues with them. Maybe consumer would like to do a review on these. Not all rechargeable are made equal, so you need to know what to buy.
While I heartily agree will all of the safety messages expressed above I would take issue with the use of rechargeable batteries. Yes, they are cheaper in the long run, but you also need to buy a charger which compounds the cost and only makes them cheaper in the very long run. My biggest problem is with usage time. They don't last nearly as long as the good diposables and in high drain devices they last no time at all. i have 2 chargers and a number of batteries - I don't bother with them any more.