Tell me about back up batteries for home/shop.

I guess it's possible! But never heard of anyone doing this, it'll be really expensive for no benefit (except in case of power cuts! - are you really that worried about the potential of 3 hour blackouts?!)
Also I wouldn't be surprised if there are long lead times with these installations.

Parrafin lamp and a good book is my back up.

Eventually the battery would be charged by solar panels so not just for impending power cuts.

Buy an electric car. Charge it.

Tesla wall bettery thing does this doesn't it?

youd still need the rectifier (charge the batteries) and inverter (to transform the DC to AC) and the electrickery to switch on and off when the power goes out.

So Battery and electronics, youd be as well buying the solar panels while your at it - get a package.

Think solar panels and kit is on around 6 months lead time just now?

Buy a small generator to use an extension when the power is out, for small essential loads.....

There’s a bit in here about charging the Tesla walk on off peak when the solar isn’t capable

As said, running batteries on trickle charge is going to be an expensive exercise.

Either do it properly or not at all.

As said, running batteries on trickle charge is going to be an expensive exercise.

Either do it properly or not at all.

Not so much these days.

I have a Tesla wall mount battery connected to my mains system fitted by the housing association, original intention was to use cheap or free overnight electricity to store in the battery for use during the day to power the air source heat pump and provide back up electricity and heating if the power went off, I enquired about solar panels on the roof to charge the Tesla battery but they'd cost £6kish.

I don't have anywhere near £6k so that idea was a no go, so at a guess id say a complete Tesla/solar system would cost you around £16000.

My air source heat pump and the battery has been switched off for near enough a year, air source heating/hot water is ****in useless and the battery used an amount of electricity per day to cycle/keep itself warm/cold with the internal thermal management so that got switched off as well.

I opened up the fireplace and fitted a log burner instead.

I have 4kw solar and 10kwh batteries.

Total cost 12k

If I was to pick one over the other it would be solar the solar generates power it roughly halfed my grid use.

But I quickly realised I needed the battery to make the most of the solar - takes usage from c~30% to 75-80% of what I generate.

Would I buy a battery alone -nope. Not even on an over night tarrif but your circumstances may vary....medical equipment etc. Would I rely on the grids "plan" for my medical equipment ....nope.

One thing to note - there's not enough batteries in the world to keep your chocolate at the optimum temperature .

warm/cold with the internal thermal management so that got switched off as well.

Yep downside of the retro NMC technology found in current gen Tesla powerwalls. Tech has moved on. Life4po is inherently safer. Tesla's accepted this and is moving towards it -maybe already released it on those you'll get in 12months time if you place an order.

Is it possible to charge the battery up during the night off the grid and just have it magically step in when the power goes off?

Had a chap round this morning to measure up for solar + batteries. He said yep could do exactly that, although you need an extra isolation box to disconnect you from the incoming mains when the mains goes down, so you don't electrocute anyone working on the LV system in the street etc when running off battery.

4.7kW of solar and 5.2kWh battery storage here. I wish I'd coughed up for a third battery, which would take it to 7.4kWh.

Basically the batteries mean that you can run off solar all the time, because they smooth out peaks in demand, so you can run the washing machine and tumble-dryer without troubling the grid. Without the battery you'd draw from the grid every time a cloud drifts past the panels.

East/west installation, today it was up to about 1kW by 9am, and the west panels have just dropped offline thanks to some trees blocking the sun. Hoping that when they drop their leaves this will stop happening.

Mine are set up so that in the event of a power cut the inverter will isolate L/N/PE and supply a few sockets labelled for emergency use and a lighting circuit covering the landings and kitchen. Some people will get massively hung up on regulations for EPS setup, but if done appropriately the risk is virtually zero when used for a couple of hours with RCD protection.

Had a chap round this morning to measure up for solar + batteries. He said yep could do exactly that, although you need an extra isolation box to disconnect you from the incoming mains when the mains goes down, so you don’t electrocute anyone working on the LV system in the street etc when running off battery.

While the end result is the same. It's not done like that unless your buying some nasty equipment.

The inverter handles the switch over. What you need to do is(correctly) set up a TT earth system and pull your key circuits into their own circuits away from anything high drain (hob/shower/oven)

While the end result is the same. It’s not done like that unless your buying some nasty equipment.

This is a Huawei system and apparently it needs an extra box to isolate the system and tell the inverter to work when the mains feed has gone.

The inverter handles the switch over

The inverter is going to be installed in the roof, so it can't isolate the LV network as it's no where near that. I would assume the isolation switch will connect to the meter tails out of the meter and disconnect the house from the LV network there.

Mines in the attic....

But I guess folks are quoting to fit what ever they can get hold of just now due to silly lead times.

Mines in the attic….

Where is your meter though?

A photo of your consumer unit set up would be useful....

It's not in the attic.

Its in the upstairs cupboard at the other end of the house.

Many ways to skin a cat but if your having to switch it over it's not really a back up system more a bank of batteries you can turn on if your there.

I'm not at home but there's a feed coming off the other output on the inverter. Feeding a main switch in a 4 gang CSU where I've got the lighting and sockets +fridge freezer and boiler wired in - these no longer go through the main CSU. And the the earth arrangement is running outside to two independent but linked 4 ft 5/8" earth rods.

If I pull the main incomer fuse- the power to the sockets and lights stays up via the inverter. But all the high drains go dead which saves other occupants of the house trying to shower or use the oven during any outages.

OK, so you've moved some circuits off the main CSU and they connect, via a mini CSU, direct to the inverter.

The setup that has been suggested, will just connect the inverter into the consumer unit and power everything / anything via that.

Hence, it would need an isolation switch to work fully off grid.

We don't really have any high drain electric appliances, so a 6Kw inverter can probably cope with everything inc the oven (can't recall how many kW that is). Plus it would only be used once in a blue moon.

Just like their cars - yet another aspect where Tesla has the integration of the systems markets sewn up.

Tesla gateway.

What size of battery bank are you fitting to go ahead with making all the systems live in a power cut ?

What size of battery bank are you fitting to go ahead with making all the systems live in a power cut ?

Awaiting a quote. It's modular so can always add to it later.

We virtually never lose power in the City so this would only be for exceptional circumstances like 3hr rolling power cuts in winter, where I'd want to keep the CH running and need power for the boiler + pump etc.

Although be interesting to see how much solar we actually get in winter and what battery state we achieve etc.

Solar will be 9 panels which were either 425W or 475W each, can't recall what he said.

Awaiting a quote. It’s modular so can always add to it later.

an observation from watching others do this.

Technology is moving forward so fast that many company’s are updating their equipment often.

Lots of people with gen1 batteries now can’t add due to them not being compatible with latter units.

That drove me to fit my 10kw all at once because that’s my average daily usage under normal usage. Figured my use under power cuts would be less so would last longer.

But do your math and I suggest buying to fit your needs upfront unless you think you’ll do the more units very soon after install.

A quick look on various Huawei supplier websites suggests the batteries go in 5kW blocks, so imagine that would be the starting point. Our average daily use is 8 Kwh over the year.

Any good websites for entering size of panels and latitude / aspect and getting a predicted solar generation by month?

Pvgis is the main one. And seems to be fairly accurate

Pvgis is the main one. And seems to be fairly accurate

Thanks, looks good.

So 9 panels x 425 Watts IIRC and we get this:

[url= https://live.staticflickr.com/65535/52437382441_babd24d272_z.jp g" target="_blank">https://live.staticflickr.com/65535/52437382441_babd24d272_z.jp g"/> [/img][/url][url= https://flic.kr/p/2nTHhUH ]PV output[/url] by [url= https://www.flickr.com/photos/brf/ ]Ben Freeman[/url], on Flickr

So in Jan we'd only generate approx 30 kWh ie 1 KWh per day, so not enough to fill a 5 kWh battery let alone something bigger.

So very little hope of managing off grid if we had rolling power cuts in January. Might just have to wear a down jacket instead.....

We have more roofspace, but conservation area so anything facing the street is a no go.

Pvgis is excellent, I used a couple more resources and a sun angle calculation for my Renewable Energy module that I'm going to compare to my Guinea pig's actual results (trail_rat).

Luckily I made it all in Excel so should be relatively easy to adapt for folk wanting to do a quick assessment.

That's my year to date.

Then I got a new inverter (same brand but battery ready ). It seems to give me power generation at lower light levels so I have high hopes for better readings

This is October alone. With the exception of the 4/5th when on the 3rd Mrs tr used the washing machine and tumble drier several times *because we have the battery* and drained it .... The we had 2 rainy dull days back to back we imported 6kw each day. But normally it's 1 or max 2 kw most of it is due to our electric shower. Which is going- going to fit a tank using immersion and probably solar PV

*Edit apparently I'm better at electric than posting pictures on this site...

@trail rat, quick question about your installation, is your whole property now on a TT system or just the solar fed fuse board and the other circuits still use the supplier facility?

I only have blue and red incomers on the end of a country line although it has been upgraded to 100amp in my memory of living here - used to be 80.

I was always TT although I didn't realise it and to historic version of regs which appears to have been some 15mm copper pipe bashed in through the solem and this had to be updated to satisfy the current regs so I have 2 bashed into wet soil depth in an inspection chamber 2 ft down and connected back to both boxs.

But I know you have to go TT if your TNS so your not earthing a live circuit to the mains when islanded. - ie not truly islanded. So long as you don't have mixed circuits. Between the boxes it shouldn't matter if you stay TNS on the main box.... But I don't know what the regs have to say on the matter.

Awaiting a quote. It’s modular so can always add to it later.

an observation from watching others do this.

Technology is moving forward so fast that many company’s are updating their equipment often.

Lots of people with gen1 batteries now can’t add due to them not being compatible with latter units.

That drove me to fit my 10kw all at once because that’s my average daily usage under normal usage. Figured my use under power cuts would be less so would last longer.

But do your math and I suggest buying to fit your needs upfront unless you think you’ll do the more units very soon after install.

Just gone with a 10 kWh battery so we can charge overnight on cheap tarif during winter and then run the battery down during the day and last a full day....

Just gone with a 10 kWh battery so we can charge overnight on cheap tarif

This might be of interest

I have the Tesla Powerwall

The inverter happily looks after the house if I cut the mains and a 13.5kWh battery is more than enough for me.

The Tesla system includes the contractor required by G99. It is required not to change the supply over, but to cut the house away from the mains until the mains is restored.

Basically the battery / PV needs to be cut away from the mains to allow diesel generators your DNO might be using to operate correctly and for general safety.  If you want bits of you house to remain on they need to be on the battery / PV side of the isolation point.

I am talking to the guy that wrote G98 to see if we can get that brought in line with G99, as presently G98 requires the battery / PV to just be switched off - effectively a legal requirement, though possibly honoured more in the breach.

@footflaps are “night tariffs” still a thing? I mean, obviously yes as you’ve got one, what supplier is that with, and is it a legacy thing or something you’ve recently agreed i.e. commonly available? Makes a lot of sense if you have sufficient battery capacity! I guess everyone’s a winner too as it smooths out demand on the grid, but surely everyone would do it if they could?!

They definitely are for charging an electric car...

https://octopusev.com/charging/tariff

Unclear if we can get the same for charging the battery.

Unclear if we can get the same for charging the battery.

hmmm, looking at that, I’m guessing not, as it’s only for charging an EV and would seem to be linked to the EV charging system in some way. Unless you can charge the car then charge your battery off that?!

Octopus Go and Intelligent Octopus do require you to have an electric car, but once you've got over that hurdle there's no distinction between what you use the power for during the cheap period. We're on Go Faster (as Go but different hours) and charge the EV and the house battery on cheap electricity. Before we had the battery we'd shift as much of our power usage as possible into the cheap period.

There are other suppliers, although obviously whether anyone is accepting new customers who knows. We used to be on TIDE by Green Energy UK which is a TOU tariff that has cheap off-peak periods but also expensive peak periods that would fit the bill. They specifically mention domestic batteries.

@phiiiiil interesting, thanks. Not got solar/battery yet but hope to get it sorted next year, funds allowing! Will have a look around at specific tariffs as not something I'd considered yet.

Octopus Go and Intelligent Octopus do require you to have an electric car, but once you’ve got over that hurdle there’s no distinction between what you use the power for during the cheap period.

We can arrange to have an electric car - just borrow my brother's!

Will have a look around at specific tariffs as not something I’d considered yet.

I suspect it's an area which will be rapidly changing...

We can arrange to have an electric car – just borrow my brother’s!

Im not sure if they "interrogate" your charger, they certainly ask what car and charger that you have when signing up and you cant bypass these questions without selecting from a drop down box for each. Many people may charge from a 13 amp plug and not have a specific car charger so not sure how this works.

Im not sure if they “interrogate” your charger, they certainly ask what car and charger that you have when signing up and you cant bypass these questions without selecting from a drop down box for each. Many people may charge from a 13 amp plug and not have a specific car charger so not sure how this works.

We can give genuine answers to car + charger type, so unless you have to have the car connected before the cheap rate kicks in, it *should* work*. Anyway, we'll find out in a few months.

We don't have a smart meter at the moment and Octopus are very vague about when they will install one (as in no information at all, I've submitted a request and heard nothing back).

* and if it doesn't - not the end of the world - just charge the battery off solar - although not much in Dec/Jan.