Retrofit Batteries & Overnight Charging

[cycling_mike]

Hi All,
Just getting my head around all of this so looking to learn from your experience.

We heat using storage heaters on the Economy 7 tariff. Some years ago we had a solar array fitted (3.5KW array) to mitigate the higher daytime tariff.

With the escalating cost of electricity, with worse to come, we are looking to retrofit a 10KWH battery system so in the summer months we can use more of our generated power and in the winter charge the batteries from the cheap tariff. The supplier we are talking to use " WECO batteries and the inverter is Autarco. We also use a Sollis inverter but they both work the same. "
A bit of an investment but a 6 year payback so worth it in my book.

Any general comments or things I need to think about?
The key question I have is how easy is it to switch from Summer - charge just from solar to Winter mode when most of the caharge will come on the off peak tariff. Do you have any insights on this?

Thanks

Mike

[Thebeeman]

I've just installed 10.5 Kw of batteries to do exactly what you're looking to do, I'm still awaiting a "new" smart meter to get an off peak tariff.
With my LuxPower inverter I can change when the batteries charge cycle very easily from the web based dashboard, and stop them discharging during the cheap hours. If I ever get an off peak meter I'll charge the batteries overnight during the winter and store my exported solar during the summer. Currently I'm storing and using the tiny bit of surplus solar, I have not exported any solar power since 1/8/22 when they were installed.

P.S. I used Home Energy Group, they gave me a quote when lots of others could not be bothered and installed in a short lead time.

[Oldgreybeard]

I installed ~21kWh of batteries a couple of years ago, to complement our 6kW of PV. We also use a form of storage heating, using a standard Economy 7 meter. By charging the batteries at the off-peak rate in winter and running the house from the batteries during much of the day, almost all of our electricity is at the cheap rate. This year it looks as if we are on target for about 97.7% of our total electricity usage to be at the cheap rate. The winter cost saving is significant, and when added to the additional saving from being able to charge the batteries for free in summer, with excess PV generation, the payback time looks to be reasonable.

[cycling_mike]

I installed ~21kWh of batteries a couple of years ago, to complement our 6kW of PV. We also use a form of storage heating, using a standard Economy 7 meter. By charging the batteries at the off-peak rate in winter and running the house from the batteries during much of the day, almost all of our electricity is at the cheap rate. This year it looks as if we are on target for about 97.7% of our total electricity usage to be at the cheap rate. The winter cost saving is significant, and when added to the additional saving from being able to charge the batteries for free in summer, with excess PV generation, the payback time looks to be reasonable.

Hi Oldgreybeard, what invertor are you using? is it easy to swap between PV charging of batteries & grid charging?

M

[dangermouse]

I know OGB and I have the same brand (but not model) of inverter, "Sofar" - and you can program a time period during which the inverter will charge batteries from the grid. Outside of this time it will use PV power, and battery power, to power your loads, and if that isn't enough, draw grid power.

The reason I bought Sofar, and not Solis, was because the Sofar allows you to program a max charge level for this charging period. So for example in winter you might program it to charge batteries from 00:00-04:00 up to a max of 90% charge (if your cheap power window is midnight to 4am). But in the summer you might limit the charge to 50% because you'll probably get a lot more from your panels in summer, and all that PV power would be wasted if your batteries are full.

According to others on this forum when I asked, the Solis doesn't have this feature.

This thread might be helpful: https://camelot-forum.co.uk/phpBB3/view ... =14&t=1434

[nowty]

@cycling_mike, most battery systems work in a similar way so its usually quite easy to set them to do what you want.

I presume your getting this model, I flicked through the manual but its not obvious to me how you do it.
You probably change the "Working Mode Set" (page 37), not much other info on it in the manual.
https://www.autarco.com/fileadmin/user_ ... Manual.pdf

I'm over 99% offpeak, example from a couple of days ago.

[Oldgreybeard]

Hi Oldgreybeard, what invertor are you using? is it easy to swap between PV charging of batteries & grid charging?

M

As above, a Sofar ME3000SP. Very easy to set both an off-peak charge window and to set the target state of charge during that window. In summer I just lower the target state of charge to 55%, which is enough as a backstop in case we have a dull day, in winter I increase the state of charge to about 85%, which allows the whole house to run for the day on off-peak if there's little solar generation. During periods in summer with loads of solar I'll switch the inverter to auto mode, where it won't charge at all overnight, so the house can just run on solar generation.

[nrgbod]

I was just about to pull the trigger on a Turbo Energy 5000 with 4x 5000 Pylontechs from ITS to go with my existing 4kW 2012 FIT system plus an additional 2.8kW of new panels into the DC side.
However when I installed the app on my phone last night and set up a dummy plant I noticed the overnight charging timers are limited to 24 start stop times per day and can't be programmed to start/ stop at 1/2 past the hour. This would reduce my Go off peak time to 3 hours. Also it doesn't allow a max charge % to be set, except maybe with the Smart setting if it actually works, so it looks like this inverter is not suitable for GO.
Do any of the inverters with suitable timers already mentioned allow the AC FIT system use in home/ battery alongside a DC setup?
I noticed the Sunsync ECCO 5 also has a generator port for FIT system input but it doesn't look like they support self installation.

[Oldgreybeard]

The Sofar ME3000SP. and a few others, work fine as AC coupled battery systems alongside a FIT PV system. This is what we have. Also, the timing on the Sofar allows the off-peak slot to be set to anything you want, as the hour and minute of the slot start and stop times can be set. Our winter off-peak slot is 11:30pm to 6:40am, and I have the Sofar set to charge (and switch the house to grid power) from 11:35pm to 6:25pm (the five minute buffer is just to allow for a bit of timing error, either in the meter or the Sofar).

Have a think about the US5000 Pylontechs, they are VERY heavy! I found shifting the US3000C Pylontechs to be a bit of an effort.

[nowty]

As OGB says the ME3000SP will work as you want but it does not have a phone app you can program it with. It’s a lot of pressing buttons on the front of it. It does have WiFi but more for monitoring and unless the APPs been considerably improved since I have used it.