To charge the battery overnight or not?
Posted: Thu Oct 08, 2026 9:31 am
I've had my system (4.5kwh panels+10kw battery) for a month now. My initial plan was to aim to have the battery at 100% at the start of peak period (1600 - 1900) and export 6khw during that period. My assumption was that throughout the year I'd increase the amount of overnight charging (toward full charge in winter, probably no need to charge at all in summer).
A friend suggested I use Capture Energy rather than try and do this manually. To be honest I didn't mind the manual effort (it's almost a game, really and I'm retired so it's something else to do). But still - Capture probably has a better ability to predict solar generation so worth a try.
It all seemed sensible until yesterday which has got me thinking. Yesterday where I live (South Midlands, UK) was mostly wet and dull. Looking at the weather forecast the day before I decided I would've charged the batteries to full overnight and hoped that the solar input would just about keep them at 100% until the peak period.
Capture's strategy was to not charge the batteries overnight at all. The SOC dropped to 10% by midnight and stayed that way with me importing from the grid until 15.30 when Capture put some charge into the battery presumably to carry me through the peak period.
As it happens I did get about 3kw from the solar (mostly at the end of the day) so I think my strategy would've earned more money. So my question is - did Capture screw up? Or did it take the battery cycle cost into consideration and decide it wasn't worth using the battery?
I know it's difficult without figures (and I'm going to try and put a spreadsheet together) but does this mean that arbitrage is not the way to go in winter and that during the low solar months it's better to rest the battery and use it only to avoid peak charges?
A friend suggested I use Capture Energy rather than try and do this manually. To be honest I didn't mind the manual effort (it's almost a game, really and I'm retired so it's something else to do). But still - Capture probably has a better ability to predict solar generation so worth a try.
It all seemed sensible until yesterday which has got me thinking. Yesterday where I live (South Midlands, UK) was mostly wet and dull. Looking at the weather forecast the day before I decided I would've charged the batteries to full overnight and hoped that the solar input would just about keep them at 100% until the peak period.
Capture's strategy was to not charge the batteries overnight at all. The SOC dropped to 10% by midnight and stayed that way with me importing from the grid until 15.30 when Capture put some charge into the battery presumably to carry me through the peak period.
As it happens I did get about 3kw from the solar (mostly at the end of the day) so I think my strategy would've earned more money. So my question is - did Capture screw up? Or did it take the battery cycle cost into consideration and decide it wasn't worth using the battery?
I know it's difficult without figures (and I'm going to try and put a spreadsheet together) but does this mean that arbitrage is not the way to go in winter and that during the low solar months it's better to rest the battery and use it only to avoid peak charges?