Home Batteries / Solar

Rob Rides EMTB

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Hi,

Considering some kind of home battery system, to charge on a cheap rate overnight and power the home in the day.

Anyone had anything done recently? Any particular things to be aware of and products to look at / avoid?
 

ThierryGTLTS

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Feb 17, 2020
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Don't buy cheap batteries if you want to do it yourself, for example 500€ is the minimum for a 12V/100Ah LiFePO4 battery.

Now there are complete solutions: Zendure Superbase Pro, EcoFlow Delta max and Delta Pro, Bluetti, ...

All in one Battery + charger + MPPT for solar panels + DC outputs + inverter (120 or 230V).

Have a Nice Day.

Thierry
 

baddon

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Jan 1, 2023
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Brother looked at putting in a battery bank recently for the farm as his solar is mostly exported and he get so little for it.

The guy asked him what he wanted it for and was straight to the point - If your doing it to be green then great lets get it done. BUT if for money its not viable yet with the life and cost of the battery. NOW this was prior (early last year) to the electricity price increases so not sure if this is still true as battery prices will also have increased. BUT at the time it was not quite revenue neutral when taking into account replacing the batteries at 5-8 years.
 

dobbyhasfriends

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Brother looked at putting in a battery bank recently for the farm as his solar is mostly exported and he get so little for it.

The guy asked him what he wanted it for and was straight to the point - If your doing it to be green then great lets get it done. BUT if for money its not viable yet with the life and cost of the battery. NOW this was prior (early last year) to the electricity price increases so not sure if this is still true as battery prices will also have increased. BUT at the time it was not quite revenue neutral when taking into account replacing the batteries at 5-8 years.
its worth it now, payback in as little as 3.5 years, thats without panels on the roof, just charging your battery bank overnight at off peak rate as you would with your electric car etc and then discharging your batteries during peak hours.
yes there are losses in inverters etc but you can still see payback quite quickly although like everything, this depends on your exact situation.
 

Waynemarlow

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Dec 6, 2019
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its worth it now, payback in as little as 3.5 years, thats without panels on the roof, just charging your battery bank overnight at off peak rate as you would with your electric car etc and then discharging your batteries during peak hours.
yes there are losses in inverters etc but you can still see payback quite quickly although like everything, this depends on your exact situation.
Ummm not so sure on that. Going to a so called “green” tariff you pay less for off peak to charge the bank and much much more for the peak, which happens to be for the most number of hours. During the winter months you will need a lot lot lot more peak tariff if you are running heat pumps to heat your house as guess what, you need heat mainly during the day. Now all good salesman use the summer months as the sales pitch as yes it does pay back in about 4 years purely for only lights and basic leccie to keep the wife’s hairdryer happy. Throw in heat pumps in the winter and it’s costing you big time. Sure you can put in say 20kwh battery banks but you may not be able to charge them in the few off peak hours you win on and you will shorten the life of the banks through constant full charge / discharge cycles and they will cost a lot in short term investment.

I have done a whole series of calculations trying to work out the U.K. sweet spot for green and even off grid electricity and very little of it actually works over say a period of 5 years to pay back the initial investment ( beyond 5 years we have no idea of technology nor cost ) let alone what the cradle to grave of manufacturing cost to the planet is. Where I think for my quite largish abode is to only fit enough battery to cover my needs from March to October, charged using solar panels and not exporting to avoid the only available tariffs that allow you to be paid for excess and not pay extortionately for the peak tariff ( some countries will only allow equal rates for export and normal usage, well done those countries ).

Where we should be winning is if we could use our electric car batteries to balance out our house needs, but then Tesla would be the first to cut off any battery warranty. Equally right now on peak rates you could have your own diesel generator running on heating kerosine and produce cheaper electricity, how have we got to that scenario ?

Theres also a new arrival on the scene, both Tesla and Octopus will fit batteries on a lease basis as long as they get paid by the government to use your batteries for peak electricity times. Sadly if we had a government being advised by the well versed rather than the present numpties who have gone for wind rather than water power, we would have all had battery banks fitted built by the startup battery company’s in the U.K. which they already subsidise and there would be no need for at least one nuclear power station which is still probably 15 years away.
 
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Rob Rides EMTB

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2 EV’s in the household,

Intelligent Octopus KWh is 10p for 6 hours and 42p rest of day.

Actually works out a lot cheaper collectively for our household if I can store the 10p rate in a battery that has charged overnight at the low rate, and power the entire house solely the battery energy that has charged at the peak rate.

The goal is to have as much of the house covered by the 10p rate.

Before EV’s we were using 10,000 KHW a year in our household.

I’d save approx £3.50 a day / £1200 a year on my calcs.
 

dobbyhasfriends

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Ummm not so sure on that. Going to a so called “green” tariff you pay less for off peak to charge the bank and much much more for the peak, which happens to be for the most number of hours. During the winter months you will need a lot lot lot more peak tariff if you are running heat pumps to heat your house as guess what, you need heat mainly during the day. Now all good salesman use the summer months as the sales pitch as yes it does pay back in about 4 years purely for only lights and basic leccie to keep the wife’s hairdryer happy. Throw in heat pumps in the winter and it’s costing you big time. Sure you can put in say 20kwh battery banks but you may not be able to charge them in the few off peak hours you win on and you will shorten the life of the banks through constant full charge / discharge cycles and they will cost a lot in short term investment.

I have done a whole series of calculations trying to work out the U.K. sweet spot for green and even off grid electricity and very little of it actually works over say a period of 5 years to pay back the initial investment ( beyond 5 years we have no idea of technology nor cost ) let alone what the cradle to grave of manufacturing cost to the planet is. Where I think for my quite largish abode is to only fit enough battery to cover my needs from March to October, charged using solar panels and not exporting to avoid the only available tariffs that allow you to be paid for excess and not pay extortionately for the peak tariff ( some countries will only allow equal rates for export and normal usage, well done those countries ).

Where we should be winning is if we could use our electric car batteries to balance out our house needs, but then Tesla would be the first to cut off any battery warranty. Equally right now on peak rates you could have your own diesel generator running on heating kerosine and produce cheaper electricity, how have we got to that scenario ?

Theres also a new arrival on the scene, both Tesla and Octopus will fit batteries on a lease basis as long as they get paid by the government to use your batteries for peak electricity times. Sadly if we had a government being advised by the well versed rather than the present numpties who have gone for wind rather than water power, we would have all had battery banks fitted built by the startup battery company’s in the U.K. which they already subsidise and there would be no need for at least one nuclear power station which is still probably 15 years away.
you have misread what I said..
discharge your batteries during peak hours.. this means you will not be using electricity from the grid during peak hours making all your consumption off peak.
you can already use some electric car batteries in this way.
your research and maths need a bit more work
 

dobbyhasfriends

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2 EV’s in the household,

Intelligent Octopus KWh is 10p for 6 hours and 42p rest of day.

Actually works out a lot cheaper collectively for our household if I can store the 10p rate and use in the day for all power to the house.

Before EV’s we were using 10,000 KHW a year in our household.

I’d save approx £3.50 a day / £1200 a year on my calcs.
yea, that compares to many of the calcs I have done for customers but this is dependant on size of house, kwH used, size of battery storage etc.
 

Rob Rides EMTB

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I reckon if I could get 20-25KWh of battery storage then it’d be possibly to cover daily house usage.

2 x Tesla Powerwalls or preferably a cheaper version of the same thing!
 

Rob Rides EMTB

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4.8Kwh here for £1700 - and they can be stacked.

Makes you realise how much we pay for a measly 700Wh battery!!

 

Mabman

E*POWAH Elite World Champion
Feb 28, 2018
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Helped an off grid, solar/hydro, friend that was looking to replace his original Lead Acid deep cell batteries and what we discovered is that it seems like LiFePo4 chemistry batteries for stationary home use are the best option, as well as cheapest.

 
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Waynemarlow

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Dec 6, 2019
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you have misread what I said..
discharge your batteries during peak hours.. this means you will not be using electricity from the grid during peak hours making all your consumption off peak.
you can already use some electric car batteries in this way.
your research and maths need a bit more work
Not at all, sure we can all go to LED lights and back off with all energy needs but come the winter, how are you going to heat your house ( please no cheating here and say gas as thats being run down, as from 2025 there's no more gas boilers allowed to be sold )? The great energy myth put out by our current government that Air heatpumps are the next big thing, needs to be looked at. Their efficiency drops back to almost a worst than a bar heater situation from below about 4 degrees, just think how many nights are below that in the UK. So most houses are going to need big battery banks to power them. Thats OK but can you charge them fully in the 4 -5 hours most off peak times are limited to. Probably not.

The only car batteries that can be used in this way as far as I understand are ones that are being reused from accident damaged vehicles ( which I'm all for ) and those that have been hacked to allow the electricity to flow. If there are such vehicles then please list them as I would be keen to look at them if I was to be looking at going leccie car. There's then the hacked cars, looking for your warranty when it all goes wrong ?

We need to explore Robs situation more, has he got when exactly he's using the bulk of his electricity and just exactly how much. Scottish Power has a really good App which you can break down usage to almost the hour, its surprising just how much is used in the off peak times. Even at his rates of 20 -25KWh batteries, those are big chunks to charge every day on cheap off peak electricity. In say 7 -8 years have you considered how much it will cost to dispose of the now dead cells, have you considered just how much it will cost to install, have you considered the cost of the maintenace of balancing the cells out at least once a year to maintain optimum capacity and longevity. Its complicated guys and we just don't appreciate just how convenient electricity as we know it, that of a single cable coming into the house is.

Don't get me wrong, I'm all for battery banks but for the vast majority of people, they would make greater savings if for example they invested in properly insulating their homes ( and I mean properly insulate ). On a recent conversion we did to create flats, I had to go back in to do about 4 hours of work in one of them. It was 10 degrees outside. With just my body heat alone and working at a reasonable pace, the temp inside the flats was rising about 1 degree an hour, I was impressed but then the flat was insulated to a higher spec than needed by current building regs. But then what happens in the summer, will those flats over heat such as the Net Zero house of the early noughties at MK which now cost more to run in the summer than the winter, having to cool the houses.
 
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dobbyhasfriends

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Not at all, sure we can all go to LED lights and back off with all energy needs but come the winter, how are you going to heat your house ( please no cheating here and say gas as thats being run down, as from 2025 there's no more gas boilers allowed to be sold )? The great energy myth put out by our current government that Air heatpumps are the next big thing, needs to be looked at. Their efficiency drops back to almost a worst than a bar heater situation from below about 4 degrees, just think how many nights are below that in the UK. So most houses are going to need big battery banks to power them. Thats OK but can you charge them fully in the 4 -5 hours most off peak times are limited to. Probably not.

The only car batteries that can be used in this way as far as I understand are ones that are being reused from accident damaged vehicles ( which I'm all for ) and those that have been hacked to allow the electricity to flow. If there are such vehicles then please list them as I would be keen to look at them if I was to be looking at going leccie car. There's then the hacked cars, looking for your warranty when it all goes wrong ?

We need to explore Robs situation more, has he got when exactly he's using the bulk of his electricity and just exactly how much. Scottish Power has a really good App which you can break down usage to almost the hour, its surprising just how much is not used in the off peak times. Even at his rates of 20 -25KWh batteries, those are big chunks to charge every day on cheap off peak electricity. In say 7 -8 years have you considered how much it will cost to dispose of the now dead cells, have you considered just how much it will cost to install, have you considered the cost of the maintenace of balancing the cells out at least once a year to maintain optimum capacity and longevity. Its complicated guys and we just don't appreciate just how convenient electricity as we know it, that of a single cable coming into the house is.

Don't get me wrong, I'm all for battery banks but for the vast majority of people, they would make greater savings if for example they invested in properly insulating their homes ( and I mean properly insulate ). On a recent conversion we did to create flats, I had to go back in to do about 4 hours of work in one of them. It was 10 degrees outside. With just my body heat alone and working at a reasonable pace, the temp inside the flats was rising about 1 degree an hour, I was impressed but then the flat was insulated to a higher spec than needed by current building regs. But then what happens in the summer, will those flats over heat such as the Net Zero house of the early noughties at MK which now cost more to run in the summer than the winter, having to cool the houses.
sorry Wayne, your information is many years out of date and clearly not based on experience and you definitely dont know much about batteries.
 
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Waynemarlow

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sorry Wayne, your information is many years out of date and clearly not based on experience and you definitely dont know much about batteries.
Wouldn't bet on that, are you the battery bank salesman by any chance ?

Would you like to quote the amps needed for Rob to charge both his battery banks and EV cars in the 5 hours he has to charge them in.
 

Rob Rides EMTB

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Would you like to quote the amps needed for Rob to charge both his battery banks and EV cars in the 5 hours he has to charge them in.
I wouldn’t be charging the EV’s from the batteries. These will be charged at off peak rate in the 6 hours of 10p from the grid.

Batteries will be used solely to power house during peak hours and 20Kw’s should cover pretty much everything.
 

Waynemarlow

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Rob, you have to add all your requirements up, I'm guessing but say 60KWh for each car + the 20KWh for the batteries + say 5Kwh just to run the house. So you could in a worse case situation need 145KWh's of energy in 5 Hours, thats some energy pull and way outside of normal single phase 240 volts incoming lines. 7KWh is the more usual home EV charge so you can work out that at most you will get is say approx 40KW's in the 5 hours from the EV chargers, not much more to charge the additional batteries before that magic 80 Amp incoming surge fuse ( 100A on a modern property ) is probably looking at being just a bit too hot to handle. :)

Sorry I don't wish to put you off but you need to consider a lot of other factors rather than just the pure " I can install two Tesla Power Banks ". Things like 4 or 5 Robs all charging their cars and their power banks on your street at the same time would pose a real headache to your leccie supplier. Any heat pump operates best at about 30 degree water temps, are your radiaters now big enough, will your electricity supply board be man enough, loads of factors here at the levels of power needed.
 
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Rob Rides EMTB

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Rob, you have to add all your requirements up, I'm guessing but say 60KWh for each car + the 20KWh for the batteries + say 5Kwh just to run the house. So you could in a worse case situation need 145KWh's of energy in 5 Hours, thats some energy pull and way outside of normal single phase 240 volts incoming lines.

Sorry I don't wish to put you off but you need to consider a lot of other factors rather than just the pure " I can install two Tesla Power Banks ". Things like 4 or 5 Robs all charging their cars and their power banks on your street at the same time would pose a real headache to your leccie supplier. Any heat pump operates best at about 30 degree water temps, are your radiaters now big enough, will your electricity supply board be man enough, loads of factors here at the levels of power needed.
I don’t think you are understanding how I am planning to use them!?

I won’t be charging cars from the batteries.

The batteries are solely to be used to capture off peak energy and power the house during peak energy prices!
 

Rob Rides EMTB

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Yes, so if your EV's are using the max available power into the house, when are you going to charge them ?
I have 100 amps at the house. A car on fast charge uses 32 amps. Would only charge one at a time.

That leaves 68 amps for the little we run off peak, and is a big overhead to charge a 20Kw battery overnight (for example) with plenty left over, even if one car is on fast charge, and another is on slow charge on 13 amps.
 

Waynemarlow

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@Waynemarlow this might help:

I had already seen that and there is a very large flaw in the way he calculates the savings. He only takes the variable rates of peak and non peak on say an EV tariff. What he should have done is taken not the EV peak rate but the rate a normal non tariff rate would be.

For example my neighbour is on an EV rate and is paying circa 42P peak whereas I on a non EV rate pay only 28P peak. The spread then only becomes 14P as the difference, not 30P ( you will still have needed to use a minimum of 12 P per unit ). So unless you can charge you battery fully on cheap rate electricity every day and do not use anymore than in the batteries ( if you do you are now paying 14P more than you needed to have and are now eating up any savings ) + you have to add in the additional cost of the batteries and installation divided by the number of units say you will use in 5 years.

By my calculations there is very little savings, if any over 5 years. Where it does get interesting if say the battery pack last 10 years. But do consider most of the battery packs warranties are based on total number of discharge and recharge cycles. 1K cycles used to be the expected of LiPo packs but now some are being pushed out to 3K ( 10 years ). Now here it gets even more interesting for the Octopus Intelligent tariff, you may get more than 1 recharge cycle in a day. My friend who has an 8KWh pack is coming off the Tariff as his packs were being constantly discharged and recharged, all at his expense in longevity. Another friend has leased his packs on that basis and gone with Octopus, longevity is not his problem.
 

Waynemarlow

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I have 100 amps at the house.
It doesn't quite work that way, 100A's is the safe surge current. At 100A's constant over a period of time you would run the risk of the 16mm2 service cable you have which is rated at only 63A's constant, of overheating. You might be lucky and have a 25mm2 cable but your property would have to relatively new to have that fitted.

But do consider that at 32A's you are only charging in the 4 hours you have to charge on off peak, 32KWh's, anymore and you are on the expensive peak rate of 42P.
 

Zimmerframe

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Jun 12, 2019
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This thread is hurting my little brain. 🤯
A quick catchup for anyone not wanting to watch the mixed tennis/squash game above.

On Rob's Tarif. Daytime electric is 42 Pence per KWH. Cheap rate is 10 Pence Per KWH (1000w for one hour). He'll also pay a standing charge of about 45p a day just to be connected to the electricity supply.

Rather than paying 42p for his daytime rate, he'd like to capture and store 20kwh's (for example) in batteries on the cheap rate and use that during the day.

To do that he needs to invest in a large pile of (relatively) expensive batteries and some equipment to control the charge/discharge/change the voltages/stop the batteries getting damaged.

That then leads to the economy question.

How long does it take to pay off that investment on the 32p (42p-10p) saving he makes per KWH, also keeping in mind that the batteries and possibly other parts of his system, will need replacing over time.

If his land allows he could also build two ponds and use the cheap electric to pump water to the upper pond and then run that water through a mini hydroelectric generator during the day to create his electricity. Or just use a motor to lift an obscenely heavy weight up a ramp/pole on cheap rate and lower it to create power during the day. Gravity examples. Alternatively, he could put a load of sand in a large well insulated container, heat that to about 700c with his cheap electric and then use that heat to create electricity during the day.

The other issue being discussed is Supply.

He has a 100 amp supply (limited by the thickness of the cable to the house). Therefore 230v * 100 = 23000w he can use at once (peak)

The electric cars can charge on 32amp (7360w) or 16amp (3680w).

He also needs to pull about 3500w per hour to charge his 20000wh batteries (ignoring efficiency losses for simplicity)
 

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