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Battery charging

My boat has 4 leisure batteries, but no fixed charger.it is currently in a marina with 240 v power available, will a normal car battery charger be sufficient to charge the battery bank, and if so how should it be connected? I am not intending to leave it on unless I'm there. I am currently having to run the engine to charge them, although I have two solar panels at this time of year they are not sufficient to make up for the power I use when aboard.

Asked by: Kevin Cracknell  | 4.15pm, Tuesday 18 November

WW says:

A car battery charger can be used to charge up your batteries on a temporary basis; simply connect the crocodile clips to the battery terminals. This however is not the best solution as the Boat Safety Scheme does not allow crocodile or temporary battery connections as they can overheat and cause fire; and car battery chargers are often not specified for long term use.
The best solution is to install a marine multistage battery charger which can be left on and will keep the batteries in tip top condition. This will be permanently wired in with fuses close to the batteries. The charger will charge at a high rate until it detects that the battery is fully charged: it will switch to a low current float mode to maintain the fully charged state. Some also have anti-sulphation pulse modes which switch in occasionally to condition the batteries. Separate outputs enable independent charging of the starter and bow thruster batteries as well as the cabin.
Although it may seem to be an expensive option, the money saved through increased battery life usually justifies the investment.

Rupert Smedley  | 6.23PM, Tuesday 18 November

Also, to add to Ruperts comments, a car battery charger will not produce enough current or sufficient voltage to adequately charge the batteries- a general rule of thumb is a current production in amps that is around 10% of the capacity in amp hours. So, for example, four leisure batteries of 110Ah each would need a charger of around 40A. Smaller chargers will be ble to return some of the charge, but would be unable to bring the battery up to a full state. You might find that the internal resistance of the battery causes some cheaper automotive chargers to either shut down early, or the converse, and keep working hard until they overheat. Just a word of warning there- keep an eye on the charger, and ensure that it is kept well ventilated, but also dry, and don't expect anywhere near the performance of a dedicated four-stage charger

Mark Langley  | 10.31PM, Tuesday 18 November

Readers say:

Many thanks, could you suggest a suitable charger, I have four 110 ah batteries, plus engine and bow thruster batteries.

Kevin Cracknell  | 7.57PM, Wednesday 19 November

Could you suggest a suitable product that will do the job, I have four 110ah batteries, plus engine and bow thruster which are separate.

Kevin Cracknell  | 11.18AM, Friday 21 November

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