question

pleriche avatar image

SmartSolar with ungrounded batteries

Hi,

I am busy commissioning an ESS system using a Multiplus II, SmartSolar and Pylontech batteries. The latest draft South African regulations recommends that the battery terminals be left floating (i.e. neither + nor - are grounded), whereas Victron recommends that the negative battery terminal be grounded.

Because of the potentially large fault currents that may be involved (and thus requiring thick cables) I am tempted to cut costs and effort and not ground either battery terminal, leaving the batteries floating. (The chassis for the SmartSolar and batteries will still be grounded, as well as the PV array frames.)

Is this configuration supported by the SmartSolar? Can I expect any operational issues if I go this route?

Thanks!

Pierre

battery connection
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

The SmartSolar works perfectly with a floating/ungrounded DC bus.

This is also very common in many parts of the world.

One other important thing is that depending on your regional wiring rules, this may also necessitate using double pole circuit protection on the DC side.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

nigelfxs avatar image
nigelfxs answered ·

I have a similar setup (Multiplus-II 3k, BlueSolar 150/70, BlueNova Battery) and it works perfectly without directly grounding the battery-pos or battery-neg.

I have added robust overvoltage protection (referenced to Earth) on the PV inputs. This ensures that PV-neg and battery-neg remain at a reasonable voltage relative to earth (since battery-neg is internally connected PV-neg in the MPPT).

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.