question

dave-warnock avatar image
dave-warnock asked

We will have both 48V (motor) and 12V (house) battery banks. Do we connect to a common earth

We are confused after reading Wiring Unlimited about what needs earthing on our boat.

We will have a 48Volt 1200AH battery bank for the electric motor only.

Our house battery bank is 12Volt 480AH.

We have 2 x Victron 2000Watt Inverters from the 12Volt bank.

Wiring Unlimited talks about earthing batteries but I am concerned about connecting the negatives of the two battery banks together. Intuitively it doesn't make sense to me.

But other sources talk about floating DC systems.

So I'm confused.

Thanks for any help.

wiring
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1 Answer
ben avatar image
ben answered ·

You can float a dedicated battery that is at a touch-safe voltage, sure. Be certain the everything in the circuit (motors, chargers) is fully isolated from the house bank, though, so you don't introduce an inadvertent return path that is not big enough to handle a fault current.

It's best to work with an electrician if the tradeoffs, requirements, or the physics aren't clear to you. You're building a large system; the cost to get expert advice is a rounding error here.

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