Any electricians on here? Question about wiring my house to run on batteries.....

snedie

snedie

snedie

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26 Aug 2009
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1,299
Okay just to start, if you don't have a clue about electrics and are just here to yell "That's ****ing stupid you **** head, batteries are 12v not 240v" or "That's a very expensive idea" then please don't bother commenting.

Onto the serious stuff. I'm looking to run my house off of deep cycle marine batteries (Around 5000 Amp Hours worth, so around 6-8 batteries), which would be charged on the night when the line switches to a cheaper rate (Economy 7).

There is a reason I'm doing this, simply because energy prices are only going up and this system will earn it self back within 3 years, after that I'm just saving more and more wonga.

The reason I need an electrician is to ask how feasible it is to rewire the main breaker unit with a modern DIN rail unit which can support the switching hardware responsible for automatically switching between various states along with all the breakers for the house and any other safety devices:

- Charging (Off peak hours)
- Standard (Battery)
- Grid (Backup)

Obviously I'm not going to attempt any of this myself, I've seen first hand what electricity can do to a human and suffice to say I'll be leaving this one to the experts.

Please feel free to share your honest ideas and opinions, even feel free to throw some rough costings to what you think an installation like this might cost (Exclude the batteries).

Thanks guys :)
 
I'm no expert, but if you're charging and discharging batteries every day they'll be spent by 3 years. As far as I'm aware there's no batteries that will endure that.
 
It's doable.

I have no idea where to start, but "Photonvids" on YouTube did exactly this to his house. He's an electrical engineer, but not your typical braniac.
 
snedie said:
this system will earn it self back within 3 years..feel free to throw some rough costings to what you think an installation like this might cost..
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are you sure this will pay for itself within 3 years?

would be better off buying some algae and using it to process your poo to produce biofuel, imo.
 
I did a bit of googling and 5-8 years seems to be the lifespan of the batteries. That would mean that after 3 years is up you have another 2 years savings to offset against the cost of replacement batteries, if you can do this then you can theoretically make a saving.
 
The Halk said:
I'm no expert, but if you're charging and discharging batteries every day they'll be spent by 3 years. As far as I'm aware there's no batteries that will endure that.
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With deep cycles as long as they are charged shortly after being discharged their life span is pretty long, something in the region of five years. What damages them the most is leaving them in a constant state of under voltage (so, uncharged) as the electrolyte can crystallise and that means new batteries.

At any rate, even if they last just for the three years they will have been a zero capital investment and it would be as simple as flicking the switch to run off the grid 24/7 there after. They will also still sell for a good price if they hold a decent charge, people want them for golf buggies.
 
The Halk said:
I did a bit of googling and 5-8 years seems to be the lifespan of the batteries. That would mean that after 3 years is up you have another 2 years savings to offset against the cost of replacement batteries, if you can do this then you can theoretically make a saving.
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Also need to factor in rising energy costs, given that we recently saw a rise of 20% (?) the sooner I get this installed the more savings there are to be made.
 
Bigpops said:
It's doable.

I have no idea where to start, but "Photonvids" on YouTube did exactly this to his house. He's an electrical engineer, but not your typical braniac.
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Just happens to be where I got the idea, unfortunately he is very reluctant to share any info on it, which is understandable I'm sure he doesn't want to run the risk of people frying themselves.
 
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ZG002 said:
Not a clue about charging the batteries and the switch over equipment needed, But you wouldn't have to change your existing CU, Just the tails feeding it.
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The switching equipment is pretty simple, it's a basic timer that activates a charging unit at a specific time at shuts it down at another. The reason I want to switch the entire box out is because there simple isn't enough room to house the rest of the gear with the current one. A newer unit would be more compact and give me wall space for an inverter.
 
Wouldn't be too hard fitting a enclosure (smaller) like the one I've linked too. You can get din rail mounted timers. For your back up you could run through a din mounted contactor running from a switch, Or Run on a normally closed connection and power the coil from the batteries, So if they go dead your contactor drops out switching you to the grid.
 
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[FnG]magnolia;22230926 said:
What kind of savings are we talking about here?
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Well I pay around £200-£250 a month just on electricity at the moment, using this method would drop that to around £150, maybe lower depending on the price I can get from a supplier for economy 7: Some of them will do deals for those who use a lot of power. Total cost of installation would be in the £3k range, I could go lower with cheaper batteries but as the old adage goes by cheap by twice. If we average a saving of £70 per month, I should see my return in around three years, maybe a little more maybe less. If we consider I only earn £10k a year after tax, saving £1k a year is a pretty substantial amount, that's like two new GPU's every year :D

It also opens the door for solar panels too, but considering that a slight film of dust can reduce their performance by over 20% (Or so I'm told) having them cleaned every other week defeats the point. Not to mention those cost £8k for the low power ones, the energy company would have to be paying me a lot to buy the electricity to justify them, and using it to charge the batteries would be fruitless.
 
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ZG002 said:
Wouldn't be too hard fitting a enclosure (smaller) like the one I've linked too. You can get din rail mounted timers. For your back up you could run through a din mounted contactor running from a switch.
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Exactly what I had in mind, some kind of a cross over to separate the entire battery system from the house and run purely off the grid. I'll need this functionality anyway, last thing I want is for some poor guy down the street who gets told the power is off to shove his hand in a cabinet and get buzzed.
 
Yeah,

In that case Run on a normally closed connection on the contactor and power the coil from the batteries, So if they go dead your contactor drops out switching you to the grid, When they come back on contactor pulls in taking you back off the grid. It's one way to go about it anyway.
 
Gonna be a PITA powering down all your PCs etc every day :p

And your electricity bill is obscene, how many people live at your house?
 
shoes said:
Gonna be a PITA powering down all your PCs etc every day :p

And your electricity bill is obscene, how many people live at your house?
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I won't need to, the power will never be interrupted and the batteries will provide me with at least 6 hours of "gaming" every day, but a more reasonable period is around 10 hours with an average of 500 watts throughout the house: Washing machines etc will run off the grid. Also if needs must adding more batteries is an option, but there is a point where the amount saved doesn't cover the cost of the batteries. I want to save at least £700 a year to justify this project, any lower than that and replacing the batteries every 5 years would cost to much.

The reason the power bill is so high is my fault, my room alone can draw almost 2kw when I'm hammering the hell out of my pc: IE folding which uses 850Watts, then my music amp and sub which come in at 300Watts average, plus an air con unit which hammers 300Watts plus other odds and ends. I also have a full server farm which I use for general studies, that bugger can draw 1.5kw too.

It all soon adds up, especially when you consider that at 18p an hour I can easily average £3 per day on my own. Then you can factor in an electric oven, dish washer, washing machine and dryer, microwave, kettle and deep fat fryer. Those lot alone can romp up a few quid a day too. We do get quite periods throughout the year when I'm in full time seasonal work, prices then drop to near £120 Avg. During these periods I would switch the larger items to run off the batteries as I won't be needing any of the power, or no more than 1Kw/h a day.
 
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Off the top of my head, you need an inverter to match the voltage, frequency and phase to the mains, like you would use on a solar panel install. I could also be wrong, but you might find it easier with a higher number of batteries so the (series) voltage is higher. When you use a lot of batteries in series (e.g. in an electric car conversion) it is a good idea to be able to charge the batteries individually, rather than leaving them all hooked up in series. That way they all get an equal charge and their lifetime is significantly improved.

I think 3 years life is a bit optimistic. Maybe think about over-rating the batteries somewhat so you don't draw too deep out of them. The farmer who lives next door to a bloke at work uses old submarine batteries on his renewables setup :)
 
Jonny69 said:
Off the top of my head, you need an inverter to match the voltage, frequency and phase to the mains, like you would use on a solar panel install. I could also be wrong, but you might find it easier with a higher number of batteries so the (series) voltage is higher. When you use a lot of batteries in series (e.g. in an electric car conversion) it is a good idea to be able to charge the batteries individually, rather than leaving them all hooked up in series. That way they all get an equal charge and their lifetime is significantly improved.

I think 3 years life is a bit optimistic. Maybe think about over-rating the batteries somewhat so you don't draw too deep out of them. The farmer who lives next door to a bloke at work uses old submarine batteries on his renewables setup :)
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I would love a submarine battery, however the neighbours might have something to say about me lifting a 4ton battery unit over their house and into my garden :D. And yes, I am being quite optimistic with my numbers but until I can get an actual qoute from some suppliers it's hard to do otherwise. If I can't get less than 12p/Kwh than it probably won't be worth doing.

Also running the batteries in a fashion that would increase the voltage to something useful like say 110 would be very expensive. I'm going to use something in the region of 6 12v batteries, any more than that and the cost outweighs the return unfortunately.
 
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