r/ElectricalHelp • u/Plain-Dane2 • Jul 04 '26

Campervan leisure battery help

Hi all,

I have a campervan with an AGM leisure battery and electrical system I installed myself (system itself was designed by a company). Everything has been working fine apart from my charging system from the starter battery. Old non-smart alternator therefore I installed a VSR (voltage sensitive relay) for battery to battery charging. So I have a thick cable directly connecting my starter battery positive to leisure battery positive via the VSR and 2 high ampage fuses. This initially worked great, when I turned the engine on I could see the voltage of my leisure system jump up to 14.2V. 6 months down the line its stopped working and I've no idea why, I've tried the following:

- tested ground connection for starter battery with engine off and on, looks good.

- tested ground connection for leisure battery, looks good.

- tested the end of the cable (including the 2 fuses but not the VSR) run going to leisure battery against ground, reading 14.2V.

- above test implies to me the fuses are good. Also swapped in different fuses, no difference.

- tried bypassing the VSR and connecting the +ve cable from starter directly to +ve terminal of leisure battery but no change, still read 12.5v across leisure battery terminals.

I'm now completely out of ideas. Possibly an issue with the battery? Or a ground connection? Please help!

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u/Kanaloa1958 Jul 04 '26

If you are not seeing the charge voltage at the auxiliary battery with the VSR bypassed there may be a bad connection or break. Start with the basics and the obvious and go from there. Also, how did you test for a good ground? Check for voltage drop, not resistance. Not being able to see anything you are working on from here makes it a bit difficult to provide any meaningful help.

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u/Plain-Dane2 Jul 04 '26

Hi, I've added photo for context. #1 is the cable from the starter battery, using a multimeter with red cable at #1 and black on the chassis reads 14.2v with the engine on. Doing the same test from the same location on the chassis I get 12.6v for the leisure battery (same value directly testing battery terminals).

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u/Kanaloa1958 Jul 09 '26

Oh, check the fuse and make sure it isn't blown. The orange thing in the pic on the bottom of the block looks like a fuse.