2nd Under Seat Leisure Battery - simple way to wire it up

[Adeybruce]

I've got a JX Westfalia, therefore vehicle battery in the boot and leisure battery under the driver's seat. I want to pop a battery in the spare underseat compartment. There appears to be a bung at the bottom of the compartment leading to the underworld. Couple of questions if I may:

- easiest/best way to run the wires between underseat compartments?
- what size wires do I use (got a spare set of jump leads - could I rob the wire off them, or is this over doing it?)
- just to check, wires run pos to pos, neg to neg - any other alchemy required?

Many thanks for any advice that you can offer

[kevtherev]

You can never overdo wiring..thicker the better
Connect the batteries in parallel
Try and keep them both in the same condition or one will drag the other down.

[Adeybruce]

And do you think I should I use an earth strap on the 2nd leisure battery, or run a pos and neg from one battery to the other? Sorry for the daft question!

[CovKid]

Earth strap. The chassis/body is common to all batteries you might have. Agree with Kev on chunky cables. Strong electrical skeleton makes is much easier for future projects.

I use these if I have a point where too many cables terminate at a battery positive terminal:

[Adeybruce]

CovKid, that looks like a really useful connector, and as you say saves a bundle of wires trying to connect to the post.

And do you have a battery under each of your seats? If so, do you run the wire down though the base of the underseat battery box? Thanks.

[CovKid]

I used to yes but quickly realised that the capacity of the leisure battery (and any good deal you might get on one) is wholly dependent on the dimensions of that box. For that reason I moved the leisure to a cupboard behind starter battery and can fit virtually any sized battery now. Best move I ever made on that score. Cable run is shorter too.

The junction box you see under the seat terminates in another one under the dash which now exclusively handles heavy stuff like headlights, rad fan and blower fan. Believe me, I have VERY bright lights now.

[kevtherev]

As your joining two leisures of similar amp hour you will enjoy increased capacity, for instance two 75 ah batteries will give an impressive 150 ah...if you didn't know
One of the advantages of having an oil burner for an engine I suppose.

[CJH]

Try and keep them both in the same condition or one will drag the other down.

This is important - don't be tempted to run one down then switch over to the other. When you connect a flat battery to a full one you can get a very high current flowing between them. Treat them as a single battery bank, so that they drain together and charge together, and they'll tend to stay at the same voltage. Differences in the resistance of your wiring (cable length and rating, and terminations) will cause one battery to age faster than the other (it will be doing more work than the other), but I doubt this is much of a problem in practice unless the differences are significant.

[CovKid]

Jump leads should be man enough but bear in mind some have a very soft outer covering which may cut through easier. Make sure you use grommets in any holes in the body.

[California Dreamin]

If your 'joining' without fusing..do it right..I don't need to spell out the consequences of this positive wire shorting to ground....5 minutes in

https://www.youtube.com/watch?v=p5Mh94_CsYA" onclick="window.open(this.href);return false;

Martin

[Adeybruce]

Thanks for the advice. Battery is in and working. Thanks for the reminder on grommets; Amazon one day delivery to the rescue. Not fused the set-up, which slightly worries me but used made to measure battery cables, and grommets of course.

[CovKid]

If you check ebay for inline fuses in the 30amp - 100amp range, you'll find ones that take lug/ring terminals rather than spade terminals that are hard work with thick cable. Thats what I fitted. Don't run too long without fuses.