Automatic charger..

[Helga]

On the subject of second batteries - if I wanted to make some proper use of the second battery, maybe simply for a 12 volt heater and a reading light, could I simply wire up the sevices straight to the battery?

I'm thick, I know,

Cheers.

Maybe with a fuse too...

[1664]

The way most campers are wired is for the van battery to do just that; the van. Everything else runs off the leisure battery so no matter how much you drain it, the van battery remains fully charged to start the van.

The only exception to this is running the fridge on 12v but that is ONLY while the engine is running so that the alternator supplies the power as the fridge will flatten any battery in next to no time.

The 12v to the fridge goes via a relay so that you can't run it on 12v without the engine running. Likewise, the leisure battery is fed via a relay so that when the engine is switched off any connection to the van electrics is broken.

ALWAYS fit fuses to wiring, as close as possible to the battery to protect as much of the wiring as possible.

[R0B]

they make leisure battery's for a reason.a normal battery will not last long if you use it as a leisure one.this may explain it..http://www.kampenwagen.co.uk/Leisure%20Battery.htm

A starter battery is the one you'll find in the engine bay of your van, it's used to start the engine, in doing this the battery needs to produce a great deal of current, but for a very short period of time (to start a diesel, you are looking at about 200 to 400 amps while the starter is operating, but only for a few seconds or so) once the engine has started the alternator is running and is putting a charge back into the battery straight away, this is how a starter battery likes things, a short but heavy discharge, then an instant re-charge.

To survive this kind of punishment the plates in a starter battery are very thick, the paste is thickly applied to stop it falling off so readily,

A leisure battery leads a totally different life, it needs to be able to supply a low current power drain for many hours on end, i.e. running a few lights at night for say 7 hours each night for a week, the TV for an hour a night and so on, it also doesn't expect to be re-charged the second any current is taken out of it, to achieve this the plates in a leisure battery are much thinner, and hence there are more of them.

You can use a starter battery as a leisure battery if you really wanted to, but they will never last that long, starter batteries hate being left in a partially discharged rate for any length of time, and they don't survive long when subjected to low current drains all the time, you can not use a leisure battery to start an engine except in an emergency, if you try and draw the kind of current a starter needs from a leisure battery, the plates will warp pretty quickly, and when this happens the battery is fubar'd, it really is best to use the battery designed for the job you intend to use it for.

[Helga]

Right, but what seems odd is that the van battery runs almost everything you would use when camped? The main inside lights, the radio, the fag sockets etc... So it seems that THAT would be the first battery to go. The "everything else off the second battery" JUST seems to be, well, without the fridge, JUST the Eberspacher heater?! A whole battery just for that?

I now do understand how it works, sort of, but just can;'t get my head around what seems to me stupid!