slight thread drift...
NiCd and NiMh do a good job.
In the early nineties (?) I wrote to CAA UK detailing the dangers of "re-celled" (reconditioned) Nicads that broadcast camera crews in the UK had begun to use.
Whilst the manufacturer of these popular camera batteries spot welded the metal strips that joined the cells the company offering the re-celling service used solder. The result one day was a solder joint broke, the metal strip slipped and created a short circuit. The battery was in transit in the back of a camera car and it caused a fire.
The crew had recently travelled on a commercial flight.
At the time there was a fuse on camera battery output, but individual cells had no protection and so a typical 13Ah 14 volt Ni-cad broadcast camera battery, if shorted internally could deliver a hundred amps.
Ni-cad is rarely used in camera batteries these days, the use of Lithium ion has enabled thermal protection for each cell and very sophisticated charging and monitoring. Of course lithium can hold its charge for many years so it is a good choice, in theory, for a standby battery.
I did not receive a response from the CAA and found it ironic that years later, following a series of lithium fores of the course of 5 years and the fire of a pallet of thousands of small lithium batteries at Gatwick Airport restrictions were put on the amount of lithium ion in a single battery enclosure (not more than 25 grams).
Yet nicads and Metal hydrides have no restrictions and are more likely to start a fire in my view, albeit a fire that is more easily extinguished than a lithium fire.
So it appeared to me that there is respect for the problems of
extinguishing a lithium battery fire, but there was (is?) less respect for other battery types that are as or more likely to
cause a fire.
Battery = kinetic energy = potential threat.
Over charging is a common cause of battery fires and since aircraft such as the A380 have 240/120volt in the seat back to power and charge laptops we haven't heard the last of on-board battery fires.