Battery Wiring Help Please

[Van Camperveld]

Hi All
I've searched the wiki but still have a couple of questions that I'm hoping someone might be able to help me with please.
I've pasted a photo of my starter battery compartment below. I have just bought a new leisure battery but haven't yet connected it as the wiring looks dodgy and is gaffer taped together and so I want to replace it before putting the new leisure battery in (have only had the van a few weeks and bought it with a dead leisure battery so this wasn't an issue).
The leisure batter has two leads off the live terminal, one of which runs directly to the starter battery and the other runs to what appears to be perhaps a relay(?) which is connected via a laptop style plug which the guy I bought it from said can be used to charge the leisure battery while driving (he showed me a laptop style plug with croc clips which he said plugged into the socket next to the starter battery and then onto the leisure battery - however he did say that he hadn't used it and so I am naturally cautious!).
There doesn't appear to be a leisure battery fuse box - instead it looks like the two batteries are simply linked and there is a single fuse box for stereo, lights etc. am I also right in thinking that the big RCB fuse box is for the EHU? It is marked 'fridge' and 'sockets' - both of which work fine off the EHU.
So my questions are as follows:
1. What cable should I use from the leisure positive terminal - what ampage, single core? Etc? I will only be running interior lights, stereo occasionally and a couple of cigar lighter sockets to charge phones etc.
2. Should I simply add a fuse box for the leisure battery and run the lights and stereo plus cigar sockets from this?
Any help would be greatly appreciated.
Many thanks
Dave



E D I T - the two positives from the leisure come under the drivers seat - one goes into the block pictured below and the other goes to what I perhaps mistakenly thought was a relay?

[CovKid]

Well, if it were me, I'd disconnect the link to starter battery and pick yourself up a relay and wire as 'split charge 3' on this page: https://club8090.co.uk/wiki/Ca ... it_charger" onclick="window.open(this.href);return false;

If you do that, leisure will charge whilst driving but be independent of starter batt when you switch off the engine. Then you can treat each battery as seperate entities. Yes you can fit smart relays, but a straightforward relay works perfectly well and will cost you at most a fiver.

Add a fusebox to leisure (even Halfords do small ones cheap enough) and run all your 'parked' accessories from that. I wouldn't run the stereo too long, they do drink juice.

Looking at it, it does look as though a relay is fitted (compare connections to diagram) but there shouldn't be a direct red to red between batteries - should go via relay.

Mine is wired this way and never ever had any problems.

In the longer term, consider replacing main cables. Most are in a bad state by now: https://club8090.co.uk/wiki/VW ... ain_cables" onclick="window.open(this.href);return false;

[Van Camperveld]

Hi CovKid
Thanks for your reply - it's very helpful - and thanks for the links - some useful reading for me there. I also saw your wiki entry about using a junction box off the positive terminal. I think I'll have to learn to solder and give this a go too.
Cheers
Dave

[CovKid]

Yep, I think if you use the diagram as a reference, and if that is a relay under the seat, next to each terminal will be a hard to see number so you trace each pin. The only way the two should be connected is as shown.

I should add, it can get a bit more complex if some dash items have been re-routed to run off the leisure. I did that with the stereo so I can sit and listen to it for a while but still have no problem starting. I also have aftermarket electric windows and discovered that it was a pain having to keep putting the key in the ignition to power them so they're on the leisure now too.

[Van Camperveld]

Cheers. To be honest I can live without the stereo as I have a Bluetooth speaker that is better quality and holds a 10 hour charge - the main use will be interior lights (currently 2x8 watt fluorescent tubes) and a couple of cigar sockets for charging iPhones etc as well as charging/running any led lights for the awning when the weather improves - so in theory a 75ah leisure battery should be plenty for a few days hopefully even without EHU.
It's a learning curve as I've never really done this kind of thing before, but it's very rewarding.
Even achieving something simple like installing a stereo and front and rear speakers gives me a sense of achievement - I'm easily pleased
Thanks again.
Dave

[AdrianC]

The leisure batter has two leads off the live terminal, one of which runs directly to the starter battery and the other runs to what appears to be perhaps a relay(?) which is connected via a laptop style plug which the guy I bought it from said can be used to charge the leisure battery while driving (he showed me a laptop style plug with croc clips which he said plugged into the socket next to the starter battery and then onto the leisure battery - however he did say that he hadn't used it and so I am naturally cautious!).

Caution seems wise, given that your predecessor proves himself utterly clueless just in that small snippet...

Basics: Let's completely ignore the second battery initially. All the time the engine is running, the alternator is putting electricity out, to charge the one and only battery.

Add a second battery in, and connect the live to the live on the first, and you have "one big battery", not a starter and a leisure. Everything connected to either battery will drain or charge both roughly equally, and they will tend towards the same state of charge. Charge one, you charge both. Flatten one, you flatten both.

That's where you sound like you are, ignoring this mystery bodge-lead. And, so long as both +ve terminals are tied together, that's where you will always be.

BUT... Disconnect the two +ves, and you can use the charge from one (now we can call it a leisure) without flattening the other. Except... How do you charge it? That's the job of the split-charge relay. When the relay "sees" electricity coming from the alternator, it connects the two batteries - and they both charge up. When the relay stops seeing that? Disconnect. Back to separate.

The charge doesn't have to come from the alternator - it could come from a mains charger to a split-charge, but there's not so much point, because the starter battery is effectively just the same as in a normal car or van, so you know it'll be just fine tomorrow/after the weekend/after your holiday.