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anders-1 avatar image
anders-1 asked

Where would I put the shunt when 2 batteries in parallel are some distance apart?

I'm trying to figure out where to locate the shunt in my setup which has a battery under the drivers seat (1) and another in the cupboard at the back of the van (2) where all the electrics are located. The battery under the drivers seat is earthed so that the load is balanced across the bank.

My question is do I need to locate the shunt near battery (1) as that is where the earth is, and run another 4m cable back from the shunt to where all the electrical equip is located at the back of the van? This would mean that the +ve supply cable would be say 50cm and the -ve over 4m. This to my mind would unbalance the load, but I'm not sure? Whats the best setup in this situation? Thanks!

BMV Battery Monitor
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JohnC avatar image
JohnC answered ·

Hi @Anders

Your batts aren't balanced properly set up like that anyway. And you don't show the 'earth return' of your loads/charger. If they all come back together into your "All electrical equip" box, then you could do it like this...

Note I've deleted the second -ve link from Batt 2.



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anders-1 avatar image
anders-1 answered ·

Hi @JohnC

Thanks for your answer and help, I appreciate it. So this would mean effectively earthing both batteries ? (as i'm guessing in your drawing shunt also has to be connected to -ve of Battery 2?) With both earthed at different points on the chassis would that balance the load properly across both batteries?

I've drawn what was my proposal to make it a bit clearer:

But just doesn't feel right with that new long cable


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JohnC avatar image JohnC ♦ commented ·

@Anders

The only real difference there is that I've used the chassis earth return instead of a new -ve wire. You could go either way.

You wouldn't need to earth at all in your scenario, and if you needed to for meeting any chassis load earths, then you'd need to earth off the Load side of the shunt, not the Batt side.

Bear in mind too that the shunt needs a data cable, and you'll have a preference no doubt for a shorter cable there too, and at which end you prefer to mount the shunt.

If you have loads using a chassis-earth-return instead of -ve wires, then the shunt in my pic would need to be relocated to Batt1. In yours it could be at either end, but then definitely no earth at Batt1.

Hope this makes sense.. :)

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