ME 4072 Postbag

[KWILParticipant @kwil]

Reader Keith enquires about Clubhouse power.

Website http://WWW.12VoltPlanet.co.uk has an interesting article in the October Newsletter regarding Victron brand control equipment

[KWILParticipant @kwil]

Off Grid Solar Power

[Clive FosterParticipant @clivefoster55965]

Interesting but the one bit I don't see is any mention of predictive battery state of charge monitoring when using off peak power to charge the home storage batteries overnight.

Important in the UK where we have a large difference between shortest day and longest day length.

Even without battery storage I buy relatively little electricity in the summer. Long days, no heating and relatively short lights on time in the evening coupled to a bit of care when cooking and laundry mean my 4KW nominal, about 3.5 KW actual, of panels can provide most of what I need during the day. Opposite during the winter where the panels can't help much. Midsummer quarter bill £50 ish, mid winter £250 ish at real, unsubsidised current prices.

Clearly for me the major gain would be in using the battery to shift most of the winter power purchase to off peak rates. Assuming off peak is half peak I'd be looking at something over £100 a quarter saving in winter but only £50 a quarter in summer when the panels and battery can carry the load. Call it £300 + per year. Payback period is still long.

So any system I put in will always need some overnight top up to make the best shift of grid supply to off peak. But in the summer the batteries won't need much topping up. In the winter they will probably need to be fully charged.

I imagine hard limits such as full overnight charge in winter, 2/3 rds overnight charge in spring and autumn, no overnight charge in winter would go some way to evening things out to make best use of the battery. It seems that something more fine grained would be usefully better but whether that can actually be achieved in practice is a different matter. The weather apps seem remarkably effective at local hourly predictions so possibly they could drive a decent prediction as to how much power the panels are likely to make the next day. After a while an adaptive controller should have a decent idea as to how much you "usually" use too.

Clive

Edited By Clive Foster on 18/10/2022 11:47:25

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