DIY Powerwall / Battery

[Dabop]

DC-DC buck and boost converters are pretty cheap and efficient.
Laptop and many electronic power supplies have a wide input voltage range.
They have a bridge rectifier on the input but would still work if fed from DC in their band.
A DC supply at 48, even 60 to 70 volts for example might be useful distributed throughout a home.
High enough to be useful and to keep the amperage modest, enough to tingle without being too hazardous.
I have a telco 48V / 30 amp power supply that is about 98% efficient. It could notionally supply a 30A DC ring without wasting any more heat than a 100W lightbulb. I can't imagine running more than 1.5kW of electronics in a house or workshop. You wouldn't use it to power heating loads.

You'd be surprised- most newer Australian offgrid homes use 96v nominal battery banks, with 15kw or more of inverter hanging off them!!!!

Even my own for the house is a 48v 12kw inverter- designed to run the entire house and a hobby workshop- which will be including two separate split cycle A/C units eventually, and when I want to 'play in the workshop' will have to be able to handle the lathe, mill and other heavy current users like the welders, plasma cutter etc...

(I got the 48v inverter 'cheap' as 'old new stock' as 48v really isn't used much these days except for small 'dongas' ie weekend camping cabins)

It's a LF (far superior to HF inverters for inductive loads) a 12kw LF like mine can supply 36kw for up to 20 seconds, where an identically rated 12kw HF inverter will only supply 24kw for less than half a second!!!

There is a downside however- a LF is big- and HEAVY... my 12v 8kw HF inverter can (just) be picked up in one hand- about 11kg, where the only slightly larger in capacity 12kw LF weighs in at a massive 72kg!!!

It took three people to load it into the cab of the tilt tray, and I used the winch to unload it!!!

 

[johnb80]

Anyone that's following this thread, Fogstar have some excellent battery pricing at the moment, 15 kWh including BMS and Cased for £1799. Just add an inverter (circa £800) and youre up and running with 15 kWh storage plus a 5 kW inverter.

 

[Sideways]

Excellent.
A buddy bought a tesla powerwall solution just a few months ago that gave him about 14kWh including the inverter functionality. Cheaper than my Fronius BYD gear but still cost over £7k fitted.

 

[johnb80]

Excellent.
A buddy bought a tesla powerwall solution just a few months ago that gave him about 14kWh including the inverter functionality. Cheaper than my Fronius BYD gear but still cost over £7k fitted.

Tesla Power wall is a very expensive option for battery storage, I'm sure it's superb quality but beyond my price range.

 

[Jameshow]

Anyone that's following this thread, Fogstar have some excellent battery pricing at the moment, 15 kWh including BMS and Cased for £1799. Just add an inverter (circa £800) and youre up and running with 15 kWh storage plus a 5 kW inverter.

How much would sufficient solar be for such a set up.
Thinking of a off-grid mens shed using 12hwh 2x week.

 

[johnb80]

How much would sufficient solar be for such a set up.
Thinking of a off-grid mens shed using 12hwh 2x week.

Use one of the online calculators to decide. You need to input your roof details and power requirements, it will then model what you can expect from any proposed solar setup.

 

[Sideways]

How much would sufficient solar be for such a set up.
Thinking of a off-grid mens shed using 12hwh 2x week

However much you can reasonably install, it's unlikely to be enough for 2-4 months through the winter.
With 9kW (24 good panels) on our roof, we've only been averaging about 2.5kWh a day through the endless gloom of the last fortnight :-(

In mid summer, 4kW of panels in a good position would probably fill a 15kWh battery in a day.

 

[Terry - Somerset]

A sad reality for solar power in the UK - when you most need the energy domestically (Oct-Mar) you are least likely to generate it.

Solar only make real economic (and environmental)sense if used to charge an EV - a roughly average mileage of ~200 miles per week is likely to require ~50kwh. A nominal 4kw array may do this for 6-8 months a year making motoring fairly cheap!

 

[johnb80]

A sad reality for solar power in the UK - when you most need the energy domestically (Oct-Mar) you are least likely to generate it.

Solar only make real economic (and environmental)sense if used to charge an EV - a roughly average mileage of ~200 miles per week is likely to require ~50kwh. A nominal 4kw array may do this for 6-8 months a year making motoring fairly cheap!

If you consider a tariff like Tomato Energy at 5p kWh off peak, it would be hard to justify solar for car charging.