Growatt - doesn't quite reach 100% despite charge instruction

psiloc

Hi again,

I know this has come up before but I'm afraid I cannot find the appropriate topic to reply to!

Anyway I wanted to note that when the target charge level is set to 100% (i.e. very low solar forecast), the charge level only ever reaches around 94%. I am certain that this is because - even in normal operation - the charge rate gets throttled by the BMS as it approaches 100%. I believe this is screwing up your calculations which are surely based on a linear interpretation of the "battery charge rate" setting.

Can I suggest you add a simple buffer of some sort to the calculation? While having the battery charge at as low a rate as possible is a great idea, I'm sure nobody would mind if it played it a bit safer. i.e. keep the same total battery target calculation but increase the charge rate a bit.

admin

psiloc Yeah makes sense though it's tricky to come up how much to add.

3%, 5%?

Happy to add a constant charge rate percentage of say 5% for now and see how we go? We could always make this an advanced user setting too if needs be.

psiloc

A setting would be ideal I guess!

For your reference, yesterday despite a charge instruction of 100% my battery stopped at 93%. It's a 10kWh battery.

psiloc

Actually I should note... I have my "battery target" correction factor set to 0.9 based on our discussions about the battery target calculation based on the solar forecast. This shouldn't be affecting this though? As the actual target in the log is fine, it's just not actually reaching it.

admin

psiloc Thats unaffected yeah, that's just used for calculating the target SOC % to reach.

Fix Released now, v0.3.394.

Avenir

Same issue with my Giv kit. Adding 5% to the charge rate sounds like a good start to me.

psiloc

Great, thanks as always!

Capt_Rich

My giv battery has the same issue - did the fix in v0.3.394 cover giv batteries too as mine still didn’t reach 100% last night. BMS does throttle back the charge rate significantly for the last 10% or so. Batteries can definitely get to 100% as they’re sitting there now after solar input this morning.

admin

Capt_Rich Yep - covered Giv too.

Capt_Rich

admin Thanks. So the fix doesn't appear to work then as I had enough slots set to reach 100%

Avenir

Last night, my Giv 9.5 + gen 1 hybrid inverter stopped charging 20 mins before end of four-hour period, 1% short of 65% target.

admin

Capt_Rich Sorry - this charge rate adjustment was not for Agile slots but for custom schedules. Agile slots' charge rate currently is set to 100%.

Capt_Rich

admin ok I understand, but if I have enough consecutive agile slots to get the battery to full charge, why does it stop at 97/98% when using WW, but previously was always 100% using the Giv app settings?

admin

Capt_Rich We're simply sending a charge instruction with a target percentage of 100% at your inverter's max charge rate, and presumably that's the same as the Giv app does.

Unless you can spot a difference from the Giv logs between what we send versus Giv app, but would expect there's no difference.

Were you doing this on half hourly basis on the Giv app or did you have a longer continuous slot too?

Capt_Rich

I can see WW sends the message to 100% but just wondering why it doesn’t get there. In the scheme of things with my battery capacity it’s not a big issue, was just more intrigued as to why.

Before Agile & WW I was Econ7 and would charge up for a block overnight and then it would reach 100%. It still gets to 100% with solar top up. Just one of those things I guess?

psiloc

This seems to be working perfectly now. Last night the target was 75% and it reached it about 25-30 minutes early, whereas the day before when the target was 100% it reached it just 5-10 minutes early. A clear example of a buffer in action and it seems to be well balanced

Avenir

psiloc Mine too completes charging 25–30mins early but is consistently 1% below the target 🤷

psiloc

Avenir If the target is being set correctly but not being reached despite there being plenty of time to spare I'd point the finger at the BMS. This should indicate it stopped charging prematurely despite the instruction.

I don't know if I'd worry too much over 1% though!

Capt_Rich

My Giv battery still sitting at 97% max when using WW - all logs and commands from WW say 100% so really not sure why it does this when it gets to 100% with solar. In scheme of things for me not a great issue as I have plenty of battery capacity