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Adding additional Solar Panels to a DC coupled battery system

bontwoody · 2026-06-18T16:28:22Z

I am currently in a position where it would be very easy to add additional solar panels to a lean too I will be constructing in the near future. I have a 2.66 kWp FIT system which has been supplemented by a 4.6kWp East/West oriented system DC coupled with a 10kWh battery and 3.6kW inverter. The battery and inverter are Huawei and the panels have optimisers. The extra panels would be West orientated and would be very useful in the winter. Their extra output, probably wouldnt make any difference to my peak output and would be clipped by the HUawei inverter anyway. Is this a sensible thing to do? Would I have to notify anyone? Would I be better trying to source another battery module instead? I seem to have a spare MPPT on the inverter so Im assuming the new panels are just in a single string with the optimisers doing their thing? Or would it be simpler to buy a balcony solar system and plug it in when required??? :-) Thanks

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Solar Photovoltaic (PV)

Last Post by bontwoody 16 minutes ago

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Old_Scientist

(@old_scientist)

Honorable Member Member

Joined: 2 years ago

Posts: 536

31/08/2026 12:29 pm

@transparent I have a question about the electrical connection for my micro-inverter. It's designed to be a plug-in device, but I'd rather make a properly protected permanent connection to the mains than just plug it in.

The outbuilding is fed by a SWA cable from the main CU in the house on a 32A MCB protected by an 80A (30mA) RCD. I very much doubt the RCD in the main CU is bidirectional.

There is a CU in the outbuilding fed by the SWA with individual MCBs for the chest freezer, lights and sockets. These are only protected by the RCD in the main CU that feeds it. If connecting the micro-inverter into this secondary CU, what type of RCD or RCBO should I specify to best protect that 800W micro-inverter?

Would you recommend we also install a SPD in the outbuilding CU as there in no surge protection at the main house CU?

Samsung 12kW gen6 ASHP with 50L volumiser and large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW). Net Zero

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bontwoody

(@bontwoody)

Noble Member Contributor

Joined: 4 years ago

Posts: 1059

Topic starter 31/08/2026 1:08 pm

@transparent Hi, so I have already bought the splices, but the hole you refer to is actually a nipple! 🙂 (Bugger, there go the midwifery students again). I would have to drill the section to insert any fixings, so Im guessing its not meant to be fixed. They do supply a much longer rail though so I suppose fixing it isnt going to be the end of the world.

I watched a very interesting youtube video with two sparkies discussing the earthing conundrum. As you say its not mandatory but they did come up with some plausible scenarios where there could be an issue. One of them actually had an arc from his forehead to a scaffold when he bent down to pick up some wet leaves from the gutter! They blamed parasitic coupling (???)

One other point against earthing it is the fact that I cant actually source the correct renusol item, to connect the earthing wire!

House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
10kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60