Why does my charge rate oscillate so much when ForceCharging triggered by HA ?

[jwob1971]

Hi

I've noticed a significant difference in charging behaviour between Mode Scheduling setup through the FoxCloud App and force charging triggered from Home Assistant. I'm wondering if I'm missing a setting or something? Currently the automation sets the WorkMode to ForceCharge, ForceCharge Pwr to 6kw & both Min Soc / Min Soc(OnGrid) to 100% but I've tried various combinations of these and other settings.

Although the batteries start charging, the charge rate steps between roughly 0.8Kw & 3.3Kw at roughly 30s intervals. There could be a sampling artifact here so the oscillation frequency may not be correct but, in any case, the mean charge rate is significantly below 6kw? When I use standard Mode Scheduling I usually see an initial period of charge around 3kw but then it charges quite happily at almost 6kw until 95%SoC or so.

In the attached image you can see the behaviour. My HA automation was triggered at 23:30 for 2hrs then ForceCharge through Mode Scheduling happened at 01:30am . You can see that the charge rate oscillates between 23:30 & 01:30 but as soon as the ModeScheduling kicks in, the charge rate becomes steady.

Has anyone seen this behaviour and fixed it ? I have a H1-6.0-E-G2 Inverter with EP5 batteries. Do I maybe need a firmware update ? I'm on 1.31/1.02/1.48 (Master/Slave/ARM) at the moment. I'm assuming I maybe need to set some other parameter or is this just some inherent BMS behaviour? It feels like 2 settings are conflicting with each other. Ideally I'd like to drive everything from HA without using Mode Scheduling at all.

Thanks in advance for any suggestions, or let me know if this has been discussed in another thread.
Cheers, Jeremy

[Will]

Can you confirm exactly how you're invoking a force charge with HA? I have a H1-gen2 WL on my test bench and it works fine with HA force charging.

[Dave Foster]

A few things to say as you have a lot going on, you can’t use the cloud mode scheduler at the same time as trying to control with home assistant, they will fight with each other and as the mode scheduler is running in the Manager firmware of the inverter it will always win. You have to have mode scheduler fully disabled if you want to control things via home assistant reliably.

The home assistant doesn’t have access to Force Charge mode, that is a schedule that runs in the inverter and when running will override any settings such as workmode, minsoc etc… - instead home assistant creates a virtual force charge mode which tests various power sensors at each poll cycle and writes to the active power register of the inverter to tell it to charge or discharge.

You shouldn’t have minsoc at 100% at the same time as you use the integrations Force Charge mode as the minsoc will instruct the BMS to charge at 5A DC and the active charge register will force it to charge at the 6kW rate you specify (or the BMS max charge rate if it is lower) and so that will be another fight between charge rates to charge the batteries.

I think the 3.3kW rate you are seeing is the limit being set by your BMS as the max charge rate, it changes as temperature drops and also as SoC rises - depending on your inverter and it’s firmware version you should have a sensor in home assistant called BMS Charge Rate, this is the max rate of charge in DC amps allowed by the BMS, multiply it by your battery volts to get your charge power.
Anything with the lowest cell temperature below 20C and it will start to throttle the charge rate and with battery packs with lower voltages you’ll see the affect much quicker, but charging at 3.3kw will soon warm the batteries increasing the charge current and so charging quicker.
You should have a sensor in home assistant for BMS Cell Temp Low (and high), if you haven’t go into Devices&Services, click on the ‘1 Device’ listed in Foxess Modbus and at the bottom of that page it will say ‘+ xx disabled entities’, if you click on that you can click and enable any extra entities that are listed there.