Sunshine, but battery not charging

[David_P]

I have just under 6KW of solar panels and a ~10KWh battery array.
Whilst the sun is shining, and the panels are generating over 4Kw of electricity, the batteries have stopped charging (86%) and Im now exporting to the grid.
Some days, the batteries charge to 100%, but this phenomenon is getting more frequent, and as we move into spring and summer Im trying to understand why.
Capture from my Foxess web site available...
Thanks for any help.
David

[Ched]

What inverter do you have?
It could be that you have too much solar for the size of the inverter and its shutting down.

Also it's a bit weird that you have no data on your energy flow diagram.

[David_P]

I have a H1-5.0-E inverter. Most times, I do get a full charge and during last summer, when my panels were hitting 5.7KW, the batteries were soaking it all up.
Sometimes I find the energy flow on the web site a bit unreliable, but both the web site and the mobile app show that the panels are generating more power than the house is using, but sometimes the batteries wont fully charge to 100% and I start exporting to the grid. With British gas giving me 6p per unit, but charging 30p+, its frustrating to say the least.
Thanks in advance for any help.
David

[graham]

I have a H1-5.0-E inverter. Most times, I do get a full charge and during last summer, when my panels were hitting 5.7KW, the batteries were soaking it all up.
Sometimes I find the energy flow on the web site a bit unreliable, but both the web site and the mobile app show that the panels are generating more power than the house is using, but sometimes the batteries wont fully charge to 100% and I start exporting to the grid. With British gas giving me 6p per unit, but charging 30p+, its frustrating to say the least.
Thanks in advance for any help.
David

Could this be the same issue as I've mentioned in the thread "Set Max Charge %"?

If my battery is charged to anything over 95% SoC and there's any gap in further charging, e.g. someone puts the kettle on to make load exceed solar output, then when the solar power again exceeds load, the excess is exported. That is, it won't start charging again if my battery is already over 95%. But if the solar always exceeds load, and it starts charging when SoC is less than 95%, it charges all the way to 100% before there's any power exported.

I've double-checked that's what happens, and as far as I can see it's reliable. Also, when I first noted that the battery appeared to have stopped charging, even though it was below max SoC, I rang the support engineer from the co that installed the system. He immediately said it would do more or less as described - that there was a threshold above which it wouldn't start to charge -, though he wasn't sure if this threshold was 95 or 90%.

I've been asking if there's a control parameter for this threshold, but it seems not.

As to 6p for export vs 33p per kWh to buy, I've gone to Economy seven and am going to Octopus Fixed Outgoing. So I pay 16.82p per kWh to buy power overnight and will, when Octopus sort themselves out, get 15p for export during the day. So if I overcharge the battery at night and have to export in the day, all I will lose is 1.82p pkWh plus whatever the inefficiencies in the inverter to and from the battery are. The downside is it's 42.68 pkWh to buy power during the day. So I will then just have to charge enough overnight to ensure I can run off the battery all day, even if I get the minimum from the solar. But it's a continual dance with the weather forecast till I start being paid.

Graham

[Ched]

As to 6p for export vs 33p per kWh to buy, I've gone to Economy seven and am going to Octopus Fixed Outgoing. So I pay 16.82p per kWh to buy power overnight and will, when Octopus sort themselves out, get 15p for export during the day. So if I overcharge the battery at night and have to export in the day, all I will lose is 1.82p pkWh plus whatever the inefficiencies in the inverter to and from the battery are. The downside is it's 42.68 pkWh to buy power during the day. So I will then just have to charge enough overnight to ensure I can run off the battery all day, even if I get the minimum from the solar. But it's a continual dance with the weather forecast till I start being paid.

Graham

I don't know if you have an EV but if you don't have a look at Octopus Flux. Import between 2am and 5am it's about 20p/kwh then most of the day 34p/kwh until 4pm to 7pm then it's 46p/kwh. The good bit is that most of the day export is 23p/kwh and during 4pm to 7pm it's 35p/kwh, during the cheap import period export is only 8p/kwh.

[graham]

I've no EV and no near term plans.

I looked at flux, but there's a statement on the info page saying "we will be launching online sign-ups very soon and our team will email you to start your switch." And I was told I could get onto E7 fairly quickly and switch later if that don't suit. Also, I didn't know if 3 hours was enough to charge my battery when I started the switch to E7 and outgoing fixed. I now know it is, I can get from 10% to just about 100% in 180 mins, and I probably won't want to do that often anyway.

But if I can find a charge period and or max SoC where I'm not too often getting to 100% on sunny days and very much less often getting down to 10% before 00:30, then the cheaper, for longer night rate of E7 makes more sense - I can also make use of that period for more than just charging the battery, like having an excuse to stay up till 12:30 and starting the dishwasher, washing machine, and tumble dryer on the way to bed, so they don't come off the battery; there's no way I can last till 2am. But then again, if I have to charge to a level where I'm exporting a lot to avoid drawing grid power before 00:30; especially, if any significant amount of that is after 4pm, then the flux might be better.

It might take some planning, but maybe E7 for the winter and Flux for the summer?

Graham

[graham]

Back on the issue of my battery won't start to charge if it's already over 95%: I went and looked at my recordings. What does seem to well show this threshold is when the battery reaches 100% from solar, so the excess starts to be exported. In that case, when the solar power dips below load, then the battery discharges - obviously. But then, if the solar comes back above load, the excess is again exported, not used to re-charge the less than 100% charged battery.

The above shows parts of events of 18 March this year, with everything but SoC expanded for clarity. Early on in the day, I've twice used the oven (once in combination with the kettle) to bring the battery down below 95 percent, once to prevent and once to stop the system exporting. It also shows, towards the end of the period of solar power, the export stuttering until the battery gets down to 95%, by which time there was no excess to charge the battery anyway. But it shows the issue.

But getting the app to plot charge power as green and export as red was less fun than it was worth.

Graham

[calum]

I have a H1-5.0-E inverter. Most times, I do get a full charge and during last summer, when my panels were hitting 5.7KW, the batteries were soaking it all up.
Sometimes I find the energy flow on the web site a bit unreliable, but both the web site and the mobile app show that the panels are generating more power than the house is using, but sometimes the batteries wont fully charge to 100% and I start exporting to the grid. With British gas giving me 6p per unit, but charging 30p+, its frustrating to say the least.
Thanks in advance for any help.
David

What firmware versions do you have on your equipment? The early firmware on the Fox gear seems a bit undercooked, worth checking with your installer or Fox themselves about getting it updated.