In a bin full of old batteries awaiting recycling, what is the probability that a closed circuit will form, allowing electrical current to flow and potentially cause a fire?
鈥� It depends on the batteries. If they are cylindrical ones with insulation around the outside, then I don鈥檛 think it would be possible in a normal-sized bin. There would have to be a circle of batteries with their ends touching. The circle would have to be quite big so that the angle between any two batteries isn鈥檛 too large for contact to occur.
Eric Kvaalen, Les Essarts-le-Roi, France
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鈥� The main danger is from batteries with terminals on the same end, such as the rectangular 9-volt battery. The terminals of two batteries could come into contact, or the circuit could be completed by another conducting object. For example, a few years ago I felt something getting very hot in my trouser pocket. It was a 9-volt battery shorted out by a 2-penny piece.
Derrick Grover, Haywards Heath, West Sussex, UK
鈥� I replace the PP9 batteries, which have both electrodes at one end, in my home fire alarms annually regardless of how near they are to the end of their life. I once put a handful of them in my pocket to take to work, where there is a recycling facility. By the time I arrived, they were too hot to handle. Left any longer, my jacket may well have ignited.
David Drew, Sheffield, UK
鈥� It is easy for the terminals of lead-acid automobile batteries to make contact with the opposite polarity terminals of another and cause a high current to flow. This is the case even if the batteries are weak enough to be sent for recycling. But the odds of a fire are still rather low, depending, of course, on what else may be in that bin. Acid leakage would be a greater concern.
Nickel-cadmium and lithium-ion batteries of the sort generally used in mobile phones and power tools have terminals designed to avoid unintended contact, so the risk there is quite low. There have been instances of lithium-ion battery fires, but these were caused by internal flaws.
鈥淭he batteries in my pocket were too hot to handle. Left any longer, my jacket may well have ignited鈥�
Howard Bobry, Nehalem, Oregon, US
鈥� I used to keep steel wool in the same cupboard as some spare batteries. I was about to accuse family members of leaving a torch on in the cupboard when I realised that the iron fibre was on fire, set alight by the batteries. This is unlikely to happen with a bin of cylindrical batteries on their own, however, because you need a conductor, like my iron fibre, to make a circuit.
Keith Ross, Villembits, France
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