Running a 2nd battery in a car?

Post by **Ammo** » Fri Jul 06, 2012 6:26 pm

Not for the lude, I've just picked up a Diesel Golf estate which I'm going to convert into a mini camper

So it would be ideal to run another battery for leisure use so I don't get stranded. I'd like to be able to charge it (split charger?) off the engine but also be able to run things like the stereo/cig lighter off it

But I'm not sure how that would work

'92 Si VTEC · Post by **jjmartin349571** » Fri Jul 06, 2012 6:34 pm

I think you need a relay, my buddy has done this in his T4. He's at camperjam atm but can ask when he gets back. Try trawling some camper forums too!

Out of interest you didn't buy a £390 Mk3 Golf TDI estate did you? I Can't remember whereabouts you are but I had my eye on one myself

Post by **Ammo** » Fri Jul 06, 2012 6:39 pm

It is a Mk3 but getting off a mate at mates rates so a tad cheaper than £390 (Well a lot)

'92 Si VTEC · Post by **jjmartin349571** » Fri Jul 06, 2012 6:46 pm

Wish I could get one dirt cheap lol, I need a diesel commuter ASAP with a big boot for the dog. Good choice with the Mk3 though, they're meant to be pretty solid like all Golfs. I'll text my mate for you and see what he says about the leisure battery, but I think he just ran battery cable through a relay to charge it. I think it was an eBay kit, like everything he buys

Post by **lewd lude lover** » Fri Jul 06, 2012 6:56 pm

I set up a split relay charger circuit on my first audio build. I had a seperate battery for the rig with the charger relay in line to the front battery. Cost about £15 from a car audio place. It charges the front battery first then starts topping up the secondary.

maybe something like this?

worked a treat. never had flat battery and never suffered voltage drop on long bass notes

Post by **Ammo** » Fri Jul 06, 2012 7:10 pm

Yeah that looks like it will do it

Just need to work out how to run the stereo/cig lighter off it. The Cig lighter I could guess wire in a new one in the back as that's where it will be needed

kernow_lude · Post by **kernow_lude** » Fri Jul 06, 2012 7:31 pm

Hi, I have spent over 25 years fitting this kind of equipment.
Best to get a Deep cycle leisure battery (leisure battery will recover very well if you keep running flat. (normal car battery will do to keep cost down)

Fit battery in boot. (secure so it cant tip over)
Run a heavy cable (with 30A fuse) to a 4 pin 30A relay. connect to pin 87

run a heavy cable from the cars battery (with 30A fuse) to pin 30
run a 5amp cable from an earth point to pin 85
run a 5 amp cable (with 1amp fuse) from ignition live (not live when starter is cranking, this will stop new battery trying to back feed the main battery when starting car) (i think its black yellow or black white) to pin 86

Its best to fit your new battery on a acid proof tray to catch the spitting then charging hard.
also most new battery's have a vent tube, extend this outside the cabin if you intend to sleep in the car. this will vent out lethal gasses.

Cost $11 (plus battery)

relay $3
heavy cable meters long $5
2x 30amp fuse and holder +1amp $2
5amp cable 2 meters $1

Post by **Ammo** » Fri Jul 06, 2012 7:42 pm

Excellent cheers

So with that the leisure battery is separate from the starter battery? apart from charging? or will that allow the car to run off the leisure battery to run the stereo etc?

Post by **lewd lude lover** » Fri Jul 06, 2012 8:39 pm

no, i think that makes it seperate, so the car cant discharge your leasure battery. you just need to wire the cig lighter and the stereo into a seperate circuit off the leasure battery. you could always wire them up to a switch. that way you could choose which circuit, and which battery, they ran off.

Post by **Ammo** » Fri Jul 06, 2012 9:08 pm

Yeah I guess a wire to the stereo via an on/off switch and spliced in. That way I can run the stereo without the keys in the ignition