Battery being charged too much at night.

jhadaway

Have a PV array with peak output of 2.8KW connected to a Growatt Inverter with a 6.4kWh Battery. Setting are Solar Capacity 3KWp, Battery Capacity 6.4kwh, Daily usage 10kWh

Using the Smart Charge Schedule to charge battery at night rate and set to charge to at least 30%.

Most days however by battery is fully charged by midday as the schedule is charging above the 30% minimum on days with a good solar forecast.

This morning for example (29-04-25 00:28) wonderwatt set a 50 target when the solar forecast was 18.2kWh. With is predicted forecast I would have expected it not to charge unless below 30% SOC.

Any help would be appreciated.

admin

jhadaway Easy way to tweak would be to decrease/tweak your daily usage a bit.

Geof

Hi Similar problem- increased solar and now charging to 100% where it was not before.

few days ago
#
2025-04-28 03:56:22 34 % 11.8 kWh
Charge instruction set for 04:00 - 07:00: 47% target at charge rate of 21%

Last couple days
2025-04-30 03:56:13 91 % 21.8 kWh
Charge instruction set for 04:00 - 07:00: 100% target at charge rate of 16%

I have already reduced my usage figure

Geof

admin

Geof It's do with with a simple correction factor that we apply as a margin. There's a thread on the formulas on the forum here, I will try and dig that out and add.

Geof

Thanks Admin any luck finding this?

admin

Geof Yep, sorry!

Here it is: https://community.wonderwatt.com/d/76-battery-target-charge-level-discussion

Geof

Thank you - is the user correction factor " battery target" under correction factors?

admin

Geof Yep that’s it.

PeteC

I'm having the same problem. I've adjusted the following:
Told Wonderwatt we only use 8kWh/day (we use much more).
Set the battery target to 0.9

But we're still getting overnight charge schedules like this:
2025-05-17 23:32:11 100 % 23.1 kWh
Charge instruction set for IOG 23:30 - 05:30: 100% target at charge rate of 10%

The solar forecast has been fairly accurate. I just don't understand why it's charging the battery so much overnight.
I've currently set the Octopus Intelligent Hold Charge setting to stop it charging overnight as we had so much spare electricity. Typically we've now had a cloudy day, and the battery may run out before 11-30pm tonight.
Our WattID is recent-cake
Any suggestions?

admin

PeteC

2025-05-17 23:32:11 100 % 23.1 kWh
Charge instruction set for IOG 23:30 - 05:30: 100% target at charge rate of 10%

For your example, it looks like your battery was already at a SOC of 100%, our IOG instruction was simply set to 'charge' to the current level. I.e. keep as is. So in this case, you were simply pulling from the grid at around 7p IOG offpeak, rather than using battery.

Always look at what the battery SOC was at the point of our charge instruction and see what the delta is to target SOC we sent, which in this case was actually 0. 😉

With IOG, our main strategy is to not have the solar battery drain into the car.

Hope that makes sense.

PeteC

admin so now I need to work out why the battery was at 100% when we were away with the car....

admin

PeteC You should be able to see from the Giv portal charts that your SOC was 100% at 23:30?

PeteC

We're still having issues. WW forecast 23kWh today and I've told it we need 8kWh. It's decided to charge the battery to 84%
It was already fully charged by noon yesterday. There was additional charging in the evening when Intelligent Octopus charged our car. As an aside it would be nice to have the option to just pause the battery when we have extra slots during the day in the summer - even better if this could be calculated from generation and demand.
What am I doing wrong?
Watt id: recent-cake.

admin

PeteC This is simply the additional margin, you were on 78% SOC, and WW added a few marginal percentages.

On IOG we don't offer the option to use your battery during the default IOG window, because some users will have their battery drain into the EV.