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Superduner

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I'm hoping that somebody on the forum will be able to give some informed advice about power banks.
My house, in rural France, is heated from a woodburner back boiler and uses 3 normal central heating pumps (Grundfos). One pump takes water from the back boiler to the 800l tank in the cellar, one circulates water around the rads from that tank, and one sends a bleed flow to the solar hot water system for when it's cloudy.
We are a bit prone to power cuts in the winter, and I was thinking that a power bank would be useful to keep all the pumps running for a few hours to save having to shut the fire down (which leads to blow offs and other issues). Cuts to date have not been more than 3 hours.
I'd like it to have an associated app so that I can monitor the charge state from upstairs, and also for it to be able to supply the pumps while connected to the solar panels which will be permanently mounted on the roof (and which I know will not be able to keep up with power demand, but will at least prolong the ability to supply). My wife would like the ability to also run an induction hob/kettle.
I've resisted her suggestions to buy a generator so far, but this might be a good compromise.
Any suggestions/ recommendations?
 

Spectric

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You would be better of with just a small generator, less complexity and it would easily power the induction hob/kettle and probably cheaper. Standby power systems using banks of batteries, electronics to convert Dc to Ac and the changeover power electronics come at a price and the batterys require maintenance. They are often only used to supply power between loss of the grid supply and the backup generator coming online.

Then you have the question of the quality of the supplied Ac power, not so much an issue for the pumps but could be for the hob and of course a generator will require less room to store.
 

Jameshow

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I would suggest solar at 100w per 100amp of battery, deep cycle batteries approx 200amp per 1000w of inverter power then an inverter of say 2000w

So 400ah battery 4x leasure batteries. £400

2000w pure sine wave inverter. £200

400w solar £400

Any more detailed advice I can ask on motorhome fun.
 

flying haggis

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As spectric says a small genny would be simpler. If not already done fit a plug to the pump cables then simply start the genny, run an extension lead to the pumps location and plug the pump(s) into the extension to keep them running and you could also use a kettle and watch tv as well
 

Richard_C

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In your post you say cuts "to date" not more than 3 hours. Strikes me that a generator will keep you going however long the power cut, depends where in France you are but if its a cold winter bit that could be important. If you size your batteries to 3 or 4 hours worth you will be worrying if you get close to the limit. With a generator you just top up the fuel tank. I have an old camping gaz 2 burner hob and a cylinder to cook and boil water in long power cuts, good enough.
 

Spectric

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If not already done fit a plug to the pump cables t
Depending how the pumps are wired, use a changeover switch so you start the generator and then operate the switches so the pumps are now powered from the generator and not the grid. What you don't want is for your generator to try and power the grid!
 

SamG340

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I've got a bit of experience with solar and off grid projects

All sounds really interesting but the first thing I'd recommend to you is to cut your power consumption

batteries are expensive and run out faster than you think. For instance caravan 110amp leisure batteries seem fantastic until you realise you can only use half their capacity. 55 amps at 12v DC doesn't work out very well once you've inverted to 240v/110v AC

The chances of you being able to generate and store enough power to run an electric cooker, shower, kettle are pretty slim unless you want to throw a lot of money at it ! ( which I think would be a waste anyway)


You need to think outside the box, for instance you could get a camping cooker with a gas bottle stored away, pull it out when needs be. 12v lighting is MUCH more efficient than 240v when running off a battery bank and so on

So the first and most important rule for off grid is, you don't need to make more power, you need to use less
 

flying haggis

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Depending how the pumps are wired, use a changeover switch so you start the generator and then operate the switches so the pumps are now powered from the generator and not the grid. What you don't want is for your generator to try and power the grid!
Hence my suggestion of plugs and extension cables. Changeover switching is ott for a few occasions a year that power cuts might occur.
 

Sideways

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While planning a new solar installation, I had the goal of being able to run both the oven and a kettle from the battery. Ideally we wouldn't need to draw on the grid to cook an evening meal. So that's about 6.5kW. I ended up with a design including 16kWh of battery storage at quite a few £££ to meet that power drain spec.

There are 8kWh batteries costing £5,000 that will not deliver much more than 2kW.
The moment you want batteries that can deliver kilowatts at 240V you're into a solution that costs £000's
A genny and gas stove are far better value for occasional use.
 

clogs

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if u go the genny route just get a Honda...mines years old and used it for working away from home )with no power on site) it still starts first pull....not cheap but qual counts...
I lived in the Charante M/time for 17 years, about 30 clicks from a NUC power station and we always had power cuts.....my pumps had plugs for a fast change over....and for cooking we were always propane gas...far cheaper to run than the elec sort....
our solar water heater was gravity fed.....so once the first frost came it was drained down till the spring....
we used about 3 ton of oak in the wood boiler, which did hot water as well as c/heating...
it was 7bed converted water mill.....
ps ...the big pipe is the vent for the fosse....not attached to the sloar unit....lol...
100_1938.JPG
 

Jameshow

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While planning a new solar installation, I had the goal of being able to run both the oven and a kettle from the battery. Ideally we wouldn't need to draw on the grid to cook an evening meal. So that's about 6.5kW. I ended up with a design including 16kWh of battery storage at quite a few £££ to meet that power drain spec.

There are 8kWh batteries costing £5,000 that will not deliver much more than 2kW.
The moment you want batteries that can deliver kilowatts at 240V you're into a solution that costs £000's
A genny and gas stove are far better value for occasional use.
Those little induction hobs are pretty efficient tbh. 600w iirc

As are slow cookers.

You'll have to adjust you sights roast dinners might be tricky!

Boiling water etc a gas stove is better tbh.
 

Superduner

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Thanks for all of the great advice, and sorry for not responding sooner. Last week's storms caused some damage for me and friends which needed some remedial work.
The installer who put in the pump system quite sensibly wired all of the pumps and sensors together from the dB, as well as the solar controller on the hot water system. This means that the immersion heater is on the same circuit as the 3 pumps. Total load could well be 2Kw at times.
Short of rewiring the whole thing (which I will look at) the generator option looks to be the cheapest and easiest way, even though I like the gadgety batteries more. As I have a couple of spare propane tanks I might just go for a dual fuel model.
 

SamG340

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@Superduner

If you're planning on running a telly you might want to go for a pure sine wave generator, it's a lot smoother power

Also LPG generators are a fantastic idea. Petrol and diesel have a short shelf life, as low as 3 months sometimes but gas cylinder last donkeys years
 

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