I'm sure I've seen such a thing in the past, but I'm struggling to find anything now! I guess one option would be to use a mains charger and small inverter.
We have a 12 volt "jump start pack" that recharges from the mains or from car cigarette plug when on the move. It came with the pack but I imagine Maplins or the like should be able to supply something to do the job.
My local car accesory shop made me a 12volt split charger device, it simply plugs into the fag lighter and charges the leisure battery in the boot, cost was around £10 alternatavley like others have said, use an inverter hooked upto to a charger, no reason why that would not work either.
To connect an inverter so as to provide 240 volts for a charger which will put out 12 volts is an inefficient use of electricity and expensive. You can connect the battery directly to the socket. This will enable the battery to get the best form of charging ie 14.4 volts which will help maintain the battery in in peak condition by desulphating the plates. ( it's why car batteries last a long time)
However, you should use a thick cable (20-30 amps) and the battery should be in a container in the boot with a vent pipe to outside the car.
Whilst not wishing to disagree with anyone, the original question referred to a small (20Ah), presumably sealed, lead acid battery, not a leisure battery or similar. The maximum charging current of these is around 6A, so charging directly from the car would almost certainly damage the battery.
Whilst I agree an inverter/main charger isn't the most efficient way the question was also about charging whilst on the move, so the inefficiencies are not a major issue. A proper 12v powered charger would be better - if you can find one!
Whilst not wishing to disagree with anyone, the original question referred to a small (20Ah), presumably sealed, lead acid battery, not a leisure battery or similar. The maximum charging current of these is around 6A, so charging directly from the car would almost certainly damage the battery.
Whilst I agree an inverter/main charger isn't the most efficient way the question was also about charging whilst on the move, so the inefficiencies are not a major issue. A proper 12v powered charger would be better - if you can find one!
Glen
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Topic: Cigarette Lighter Battery Charging ??
