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NigelL

Connecting battery negative terminal to Earth?

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I have seen differing opinions on whether one should earth the negative terminal of one's Inverter battery.

My inverter's AC connections, AC Surge protection and Chassis are well earthed (Victron Multigrid-II 48V, 3KVA).

My solar panel frames are earthed as is my DC Surge protection on the input to my Solar Charger (Victron MPPT 150-70). 

The "AC-Side" and "DC-Side" earths connect together at a single point very close to where the mains power enters my property (i.e. close to the Neutral-Earth connection and Earth-rod/electrode).

Should I also be connecting my battery negative terminal to the "DC-Side" earth?

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13 minutes ago, NigelL said:

I have seen differing opinions on whether one should earth the negative terminal of one's Inverter battery.

Low voltage (less than 60V). Not required to earth it, and you should certainly not do it unless the inverter maker says so.

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Thanks! I have not seen any recommendation, either way, in the Victron manual.  The solar panel negative appears to be directly connected to battery negative on the MPPT150/70 - so it may be best to earth the battery negative to give improved protection to the MPPT.

I was wondering if there are any "regulatory" requirements in this regard - e.g. for Engineering signoff? 

 

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10 minutes ago, NigelL said:

The solar panel negative appears to be directly connected to battery negative on the MPPT150/70 - so it may be best to earth the battery negative to give improved protection to the MPPT.

I was wondering if there are any "regulatory" requirements in this regard - e.g. for Engineering signoff? 

You have to earth the frames of the panels. From frames to a earth, that's is it. Required for CoC sign-off. 

Using earthing and battery negative in the same sentence, unless it is NO, don't do it ... is very bad idea. 🙂 

Unless the equipment manufacturer says so ... like Plonkster said.

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1 hour ago, NigelL said:

The solar panel negative appears to be directly connected to battery negative on the MPPT150/70

In most of the new Victron MPPTs this is the case. In some of the older ones the current sensor was in the negative line. Because this is a hall-effect sensor you won't see it by measuring it with a DMM, but if you earthed the panels and the battery on the negative side you would bypass the current sensor and blow up the MPPT. I've seen it first hand too. But that was the old ones... the new ones have current sense in the positive line.

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The only connections to the battery, should be the inverter. Earthing means electrically connecting the utility Neutral to the battery. If the inverter is not transformer-isolated, it means the ac and dc gets connected to a common point.

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Agreed, no reason to earth it

Also no need for additional earth spikes when there is a power earth available. All metal work not carrying current under normal conditions, should be bonded to it and nowhere else.

Edited by SOLARWIND
Adding info

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