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Good negative/ground for charging second battery
I'm currently installing a second/leisure battery (through a VSR) in my berlingo van. I know I could use the chassis as negative/ground for charging but i would prefer to use a designated pos+ and neg- cable to charge the second battery as efficiently as possible (whether that's overkill or not on my setup, would be another discussion..).

Normally i would connect to the negative lug/terminal on the starter battery. However, as most of you will know, this is not very accessible and i don't wanna mess with the original wiring (which again, is not very accessible). So i was wondering what would be the best part to attach the negative cable to.

One option I was thinking of, is the lug that is bolted on the passenger side wing and is used for jump starting ( , the second photo). As its bolted on, I guess this bolting could be used to attach a cable terminal as well. Feels kinda bomb proof though and is bolted in fairly thin wall, not sure if its meant to ever be unbolted or even worse, once its off maybe not possible to re-attach! Alternative would be to use a 19mm ID battery lug to connect to it like to a battery lug.

Any thoughts or comments or other/better options would be much appreciated :thumbsup:
I think your own solution is good.A good solid mechanical connection.:thumbsup:
Strawberry flavoured windows  Dodgy
[-] The following 1 user says Thank You to ron for this post:
  • ChippyAndBeer
I take it you want to use the alternator to charge the second battery?

If so will the current alternator be able to handle charging two batterys or would it need to be uprated?
[-] The following 1 user says Thank You to homeruk for this post:
  • ChippyAndBeer
They normally cope OK.usually the batts are connected so as the car batt gets the charge until good,then leisure batt is charged.Confusedalut:
Strawberry flavoured windows  Dodgy
Hi, and thanks for your replies!

as for the ground connection i might just go for that option.. not sure yet whether i dare unbolting it (see edit of my original post) or use a battery terminal to connect to it, its 19mm diameter. Have any of you ever unbolted that thing? Bit worried about breaking it in the process!

as for the alternator, i am installing a voltage sensing relay, which splits the second battery as long as the main battery voltage is below 13.3V and splits it again if that voltage drops below 12.8V. so wouldn't i effectively charge just one battery at a time as the starter battery hardly draws any power to charge as long as its fully charged? That was my understanding of it so far, please correct me if i'm wrong. but now that you mention it i will definitely double check it!!

edit: my bad, had a think about it and once the engine is switched on and the alternator is running it provides 14V and both batteries would charge, so if one of them is relatively low there would be a higher current drawn from the alternator. I'll try to make the sums, thanks!

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