On Mon, 08 May 2017 22:11:05 +0100, bert wrote:

In article , David
writes
ssnip

Just looking for a cheap and simple way to use the spare battery
without any major electrical surgery to the car or caravan.

Charge it when the car runs, not when it isn't. The latter gains you
nothing.

Yes, I am intending to charge it when the car is running; I don't want
to flatten the car battery.
Then jut connect up a voltage sensitive relay and off you go. That's all
the caravan battery has. The regulation system on the alternator will
prevent overcharging. When you switch off the engine the relay will
ensure the two batteries are not connected in parallel.

Does this work directly off the alternator, or via a 12v cigar lighter
socket?

The requirement is for something cheap and simple which does not involve
any extra wiring in the car.

I realise the output from a 12v socket will not have the same
characteristics as a direct feed from the alternator via a charge
controller.

Cheers


Dave R


--
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64

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