Cost of adding batteries to existing PV system.

1961Nick

Although it's very unlikely at such a small voltage differential, if you don't want to risk a spark during a connection, switch the batteries off, make the parallel connection, switch them back on & leave them to balance.

QrizB

https://forums.moneysavingexpert.com/discussion/comment/82025257#Comment_82025257

While that's good general advice, I don't think the OP's batteries have switches.

They're these:

https://www.alphaess.com/Public/Uploads/uploadfile/files/20220629/Datasheet_EN_M48112-S_V08.25022021-837.pdf

WIAWSNB

Thanks folks.

You should hear the bludy spark when I reconnect the bastar…er, batteries to the inverter. Jeepers. DC switch on order.

Anyhoo, I found the nearest thing to a 5 ohm resistor - an ancient bell transformer that was in the house when we moved in! Classic.

Currently balancing at, ooh, a half-amp? A month aught to get them equal… 😀

WIAWSNB

Blimey - or just an hour.

No sparks - honest.

QrizB

Glad it all went smoothly!

WIAWSNB

Bzzzzzzzzzz!

Thanks 🙂

WIAWSNB

To conclude the title of this thread, through very fortuitous purchases - a Sofar for a reasonable £310 which came with almost all the required leccy bits included, and with some risk taken with 'unusual' batteries - I have what appears to be a decently-working 10+kWh battery system for a total of £710.

The batteries work exceptionally well with my adjustable Phev charger; when it's overcast and the PVs are generating only around 1kW or even less, even the lowest 6A setting on the EV charger would have still drawn a few hundred watts from the grid for hours. No longer - the battery provides that balance.

And it's been good fun - since it worked.

Thanks for all the help offered - priceless.

Heedtheadvice

Great Result

WIAWSNB

Since installing, I've taken a total of 3 units from the grid, and that would be from when the domestic power draw was in excess of what the batteries could provide - say when more than one large appliance was being used at the same time. The battery charge never fell below 2 bars out of 5.

Phev kept topped up enough for constant use too - nice to be able to do so even when sun is not out.

So that's roughly 1.5 units per week, instead of at least 5 per day.

Of course, conditions are pretty much ideal at the moment, with the sun having been out at least every few days, but even the very few dull days recently was enough to trickle-charge the batteries at around 300Wh.

QrizB

Hi @WIAWSNB hope it's OK to bump this thread and ask you a question.

I was finally getting around to making a data connection between my Fogstar battery and my Sofar inverter. Looking at the connectors, the Fogstar has RJ45 connectors for CANBUS and RS485 while the Sofar has what look to be RJ11 connectors.

Does your Sofar also have RJ11? What cable or adapters did you use for your data connection?

(If anyone who isn't the OP knows the answer, feel free to chip in!)