Trying to only charge battery to 30% capacity between 2am and 5am

Hello everyone!

I’m new here. Hope you can help me with something that isn’t working the way I expected.

I think I have set the charge duration on my system for 2am to 5am each morning to top my battery up to 30%.
This is the cheap tariff slot and the idea is that the battery gets topped up with cheap power that we’ll use when we get up in the morning during the more expensive tariff.
However, I am pretty sure that when the battery is over 30%, energy is still being imported between 2am and 5am.
So, two questions-

1. All the graphs seem to show what’s being imported/exported. Is it possible to see what the battery level is at certain times of the day?

2. Is this setting supposed to do what I think it’s doing? (Charge battery up to 30% in the 2am to 5am time slot)
   

Trying to make sense of this graph which appears to confirm that the grid is being used between 2am and 5am when the battery is over 30% charged.
I think I may have figured out what’s happening. Does activating this setting prevent the battery from suppling the home with energy? So during 2am to 5am the house will be using the grid?

Your house will have a small base load. The battery will stay at 30% and the grid will supply the base load. My base load is about 400w. TVs and Sky boxes on standby. Phones and laptops charging. NAS box and router, clocks in cooker and microwave, boiler pump (if running) etc
Why are you targetting 30%. Is that because you generate sufficient from panels during the day and never need daytime grid import?
If you want to get clever , try something like predbat. It looks at your import and export tariffs, looks at forthcoming solar predictions and then decides best time to charge and best time to sell,

My dashboard

Miller So during 2am to 5am the house will be using the grid?

yes - if the SOC target is reached before the end time, the battery will sit idle and the house will be supplied from the grid

I don't have predbat so work in a slightly different way to the opening post to achieve similar results.
I don't tell the inverter to charge to 30% but manage my charging and achieve approx 30% within the 2am-5am cheap rate slot. I do a 20 or 30 minute charge every hour, finishing at 05:00. This worked really well during the cold nights to help keep the battery warm.
I know there's automatic ways to do this through predbat but if just using the GE dashboard it's an easy way to achieve similar results.

Miller as others have said, when you set a timed charge 2-5am with a limit of 30%, what you are doing is:

• setting inverter to charge mode. When in charge mode it will not discharge to meet house load as its charging
• setting a charge limit of 30%. The battery will charge to this level and then stop, not go above it

Thank you. So helpful and it all makes so much more sense now.
SteveCook - That software looks very interesting. I’ll have to look into it more, trouble is finding the time to do it.
CW - I can see why the system does that if it’s reached 30%, but if it’s over 30% you’d think it would use the battery. Ah well! At least I understand how it works now.
Eco-Me - That sounds like a great idea. I shall give that a try.

Predbat and Home Assistant are free.
Just need a Raspberry Pi. I got mine free off son who was not using it

I have HomeAssistant and predbat, and I have my own (probably slightly whacky) way of limiting my battery charge overnight.

I let predbat estimate my battery load from the next 24 hours and then I use HomeAssistant to force predbat to keep the battery satising the house-load. This is the 'force-demand' option in predbat. This gives my a good idea of when the battery will be exhausted, at which point, I can open up some off-peak charging slots.

I am on the Cosy Octopus tariff because my house load is often 30+ kWh per day and my 13.5 kWh AIO and Gateway can't last in the winter for more than about 10-12 hours max.

With my 3.6 kWh solar and a nice sunny day like today, I charge my battery up to 80% or so by midnight and then leave things alone until I can see i will need more import to ensure I can charge to 80% again by midnight. I might need a small import around 11pm-midnight today

This gives me the best balance between using all my solar power with little or no exporting and preserving some battery power in case of power cuts.

I have HomeAssistant and predbat, and I have my own (probably slightly whacky) way of limiting my battery charge overnight.

I let predbat estimate my battery load from the next 24 hours and then I use HomeAssistant to force predbat to keep the battery satising the house-load. This is the 'force-demand' option in predbat. This gives my a good idea of when the battery will be exhausted, at which point, I can open up some off-peak charging slots.

I am on the Cosy Octopus tariff because my house load is often 30+ kWh per day and my 13.5 kWh AIO and Gateway can't last in the winter for more than about 10-12 hours max.

With my 3.6 kWh solar and a nice sunny day like today, I charge my battery up to 80% or so by midnight and then leave things alone until I can see i will need more import to ensure I can charge to 80% again by midnight. I might need a small import around 11pm-midnight today

This gives me the best balance between using all my solar power with little or no exporting and preserving some battery power in case of power cuts.

Weasel i’ve been leaving predbat to manage things, charging automatically overnight to fill the batteries in the cosy cheap period, then exporting whatever solar there is during the day.

But these last few days now its milder I’m using far less with the heat pump and with the greater sun I’m getting loads of grid voltage-induced inverter clipping so am having to change strategy. Hardly charging at all overnight and letting the batteries trickle charge from solar during the day. The 13.23p Cosy import rate (and after losses effectively 14.5p) is much the same as the 15p export rate. Tthe trickle charge should mean I generate more overall and its financially better.

geoffreycoan i don't get any clipping because my solar panels generate only 3.6kW and I can export this, but I decided as a thought experiment to see if I could avoid all exporting by starting off with less than 100% charge and let the excess solar trickle charge the battery. We appear to be adopting similar strategies.

I currently have set predbat to charge the battery at 23:30 only which will leave it at about 84% at midnight. I estimate that it will be at 20% or so by mid morning and I will see what the solar generation looks like throughout the day before enabling any other charge slots

I know that this way of using predbat is non-standard, but it's the easiest way to predict my battery level given the expected solar generation. I could have predbat in monitor mode and then set my charging slots in the GE app, but it is easy enough to keep setting force-demand slots with HomeAssistant and then cancelling those where I want to charge the battery

Weasel I have 44 panels with 14.2kW potential generation capacity so managing how much I export and when is a key consideration for me. It seems to be worse this year already than last, probably due to more neighbours with solar.

Today I started charging at 9:30 at 1700W with the 9.5 battery being full by about 3pm. Where the PV power drops to zero is when the inverter shuts down which became more frequent in the afternoon as the West facing arrays started generating more.

From tonight I am going to stop charging in the 10pm Cosy slot as well and then only open up a bit if I need to (like you do) to get through the night. I did have to turn freeze export off because Predbat kept freeze exporting in the cheap periods to preserve the SoC.
Am expecting that when the Cosy rates go up in April I won’t have to make as many adjustments as it won’t be beneficial to charge in the cheap rate vs exporting

geoffreycoan The freeze exporting was why i opted for specifically setting manual demand explicitly on every slot I didn't was to charge. I didn't realise that I could turn it off globally.

I currently have 2 HA automations, one for 0400-1300 which executes at 2000 and one for 1300-2200 which runs at 0515. Both of these simplt set force-demand for their respective periods. I can then manually tweak the period 2200-0400 as desired to top up the AIO.

For me, this is just a thought experiment because I know I am unlikely to generate enough solar to avoid a top up each day; nor will clipping be an issue. When the new cosy rates kick in (tomorrow) I will have a look how much freeze exporting is planned and maybe disable it, but since I am setting all slots to force demand, exporting of any kind is suppressed anyway.

Last night, I took a 30-minute top up (SoC went from 69% to 87%). Today looks set for an hour charging because the battery is forecast to be at around 45% by 10pm

Weasel yes you can turn freeze exporting (and freeze charging) off as global options in Predbat (separate switches for these).

I didn’t charge at all last night but did do freeze charge for a couple of the 10pm slots, holding the charge and ran the heat pump off grid import rather the batteries. Still ended up with 3.5kW in the batteries at 6am; was trying for lower!

Although there is some grid clipping in the afternoon, yesterday I did much better than the day before, slightly exceeding my solcast forecast, so I think the strategy is working

Predbat knows that the rates will change tomorrow as all the rates in the plan show with a ?, but interestingly the new rates are not there yet. Would have thought they’d be in the ‘next rate’ Octopus integration sensors. Maybe not loaded via the Octopus API yet.

geoffreycoan Thanks for the hint regrading disabling the freeze stuff globally. I have done just this and also set my predbat mode to "Control Charge Only".

I now only need to disable charging slots as needed and for now am skipping the 0400-0700 and the 1300-1600 periods completely. I set these up with HA automations running 16 hours in advance so I can tweak things in plenty of time to avoid exporting whilst still keeping my SoC at a reasonable rate.

Also, my new Octopus rates for tomorrow are now showing in predbat. I will leave it a few days and then maybe revert everything back to "normal" to see what effect they have. I expect a lot less exporting now the cosy rate is <1p cheaper than exporting

Weasel I'm seeing that predbat is choosing to freeze charge in the evening and morning Cosy cheap periods (now 14.14p), so grid importing for the house rather than charging the batteries up as it was before the rate change. I'll try the same setting it back to defaults in a day or so and see what predbat plans by default.

Weasel Thanks for the hint regrading disabling the freeze stuff globally. I have done just this and also set my predbat mode to "Control Charge Only"

Just be aware that Control Charge Only means that you can't set predbat to export mode at all, e.g. if you wanted to export something to reduce the battery soc to give more space for solar charging, predbat won't do this in Control Charge Only mode. I'm leaving mine on Control Charge and Discharge and its not financially viable to export so predbat isn't doing any.

Yesterday's graph shows much better result, hardly any occasions the inverters stopped generating due to high grid voltage:

I set to freeze charge for 10pm-11pm, then freeze export from 11 through to 8am to run the batteries down to near empty. I also set inverter_limit_charge to zero to prevent the batteries starting to charge in the early sun, then progressively step the charge rate up at 08:30 and 13:00.
Setting the charge rate to zero doesn't totally stop solar charging, there is a bit at about 150W, but its good enough. The batteries don't fill until early afternoon.

At the moment there is no automation of setting the limits or times based on solar forecast, will look at that as a further enhancement. Setting bulk predbat manual overrides is working fine for me with a long string of times to set

geoffreycoan

Thanks for the tip regarding Control SoC only - I will change it back