Granny charging with Batteries+PV

2531 Views 17 Replies 7 Participants Last post by Spiny, 16 d ago

Alshamal

Discussion Starter · 17 d ago

I have 12.8KW of batteries which are 100% full by lunch time! So I’ve been using the granny charger when i‘m at home in the afternoon, but i would like to do if possible would be to take 30/40% out of the batteries in the morning and then the Solar will charge the batteries back up in the afternoon when i‘m not about!

Is there a way i can just draw from the batteries and solar and stop using from the Grid!

I have a Lux 3600 ac inverter.

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Cheshirecat

· #2 · 17 d ago

Surely, everything you draw in the house IS coming from the batteries already unless your load is exceeding the inverter limit ?
This would include a plugged-in Granny

Just use a Smart plug (Tapo or similar) to time the granny and, if yours has the facility, turn the granny down to 6a….should drain batteries at 10% an hour ( less the solar at that time)
( or did you mean that the car is not there in the morning…doh)

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Mach993

· #3 · 17 d ago

If I am interpreting your attachment correctly, your batteries are currently set to charge to 60% overnight during your GO window.

Do you need the full 60% in the morning before your solar kicks in or could you drop the overnight charge % to 20-30% leaving you more room in your batteries to soak up peak generation?

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Alshamal

Discussion Starter · #4 · 16 d ago

Mach993 said:
If I am interpreting your attachment correctly, your batteries are currently set to charge to 60% overnight during your GO window.

Do you need the full 60% in the morning before your solar kicks in or could you drop the overnight charge % to 20-30% leaving you more room in your batteries to soak up peak generation?

Yes I’m on Octopus Go! The batteries haven’t been charged from the grid for days! So they are above 70% when the solar starts adding to the batteries , that’s why i want to charge from the batteries in the morning to use 30/40% into the EV. If the PV is not producing above 2kw it will draw from the grid, this is what i want stop!and control the grid input!

Mach993

· #5 · 16 d ago

Perhaps best to set the max charge current in the car to 10A, then plug in as normal in the morning. Inverter will blend battery and solar for a 2.4kW charge rate but should be enough wiggle room that it still doesn’t go over your inverter limit and start drawing from the grid - providing of course you aren’t running high power appliances at the same time.

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Cheshirecat

· #6 · 16 d ago

Why not run the Granny evening/night whilst not using the cheap rate Go

Alshamal

Discussion Starter · #7 · 16 d ago

Cheshirecat said:
Why not run the Granny evening/night whilst not using the cheap rate Go

At the moment I’ve 96% battery i will plug in the granny ,how do stop drawing from the grid?

Cheshirecat

· #8 · 16 d ago

Where is your fridge and TV currently drawing from ??

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Alshamal

Discussion Starter · #9 · 16 d ago

Cheshirecat said:
Where is your fridge and TV currently drawing from ??

From the batteries!

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Cheshirecat

· #10 · 16 d ago

Where is your fridge and TV currently drawing from ??

Alshamal said:
From the batteries!

well your granny will run from the batteries as well
If you turn it down to 6amps ( 1400 watts-ish) it should pull 11% -12% out of your batteries each hour

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Alshamal

Discussion Starter · #11 · 16 d ago

I will give it a try👍

Alshamal

Discussion Starter · #12 · 16 d ago

👍 so far so good!

robert79

· #13 · 16 d ago

Alshamal said:
Yes I’m on Octopus Go! The batteries haven’t been charged from the grid for days! So they are above 70% when the solar starts adding to the batteries , that’s why i want to charge from the batteries in the morning to use 30/40% into the EV. If the PV is not producing above 2kw it will draw from the grid, this is what i want stop!and control the grid input!

Surely if the PV isn't producing enough it should start draining the batteries before resorting to grid if inverter capacity is exceeded?

Alshamal

Discussion Starter · #14 · 16 d ago

Working fine now thanks for all your help and advise👍

divenal

· #15 · 16 d ago

Cheshirecat said:
Just use a Smart plug (Tapo or similar) to time the granny

I was under the impression that was a bad idea: starting the charge this way isn't so bad, since the car will have to first negotiate for power, then may ramp power up gently. But when stopping the charge, it will cut off abruptly at full load, which could be harmful to the various bits of hardware.

Cheshirecat

· #16 · 16 d ago

Dont believe so

Mrklaw

· #17 · 16 d ago

so far what works for me is putting the charger (zappi) in eco mode which waits for 1.4kw then continously charges. if the clouds come out it drops to 1.4kw but never goes below - so it'll draw from the battery if needed. Its a good way to 'pause' the battery and drain a little if needed. So I have two modes

- if battery is low in the morning I'll probably leave it to charge to almost full then put the car charger on. Then as the solar drops later in the day down to less than 1.4kw fairly regularly, I stop the charger and the battery tops up on the lower excess.

- if battery is still high in the morning (like over 50%) I put the car on as soon as there is consistently more than about 2kw (1.4 for the car and 300-400w for the house when I wfh). Then do the same as above

honestly if its a pretty bright day, the two cases often merge - by the time the solar is stably over 2kw the battery has already topped up a fair bit. so I don't stress about which to do - although I prioritise the battery as much as possible

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Spiny

· #18 · 16 d ago

Not a problem turning on a granny charger, breaking a 6/10A current though is not a great idea, and in this case where the electronics in the car are designed to ramp down the charge when a turn off signal is received or generated (unlock, fully charged etc.) its a bad idea. The spike from any inductances may damage the OBC. The occasional powercut may be OK but everyday?
The Zappi on eco works for me, pulling from the batteries as clouds go over.

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