Prevent battery overcharging when there is low consumption and high PV generation

[stoil]

Hello there!

First of all, I want to express my gratitude to @davidrapan for his excellent work on this integration and also to everyone else contributing to this awesome integration. It is working better than great with my Deye SUN-18K-SG05LP3-EU-SM2 inverter and DEYE SE–G5.1 PRO-B batteries. Thank you, @davidrapan .

I am very new to the solar energy world. In fact, I just had my home solar system installed two weeks ago. My system consists of:

1. Inverter: Deye SUN-18K-SG05LP3-EU-SM2
2. Batteries: 2 × DEYE SE–G5.1 PRO-B
3. PV: 21 × AIKO NEOSTAR 2p 475W panels (soon to be expanded to 37)

So far, I have only used David's integration and customized the deye_p3.yaml profile to reduce the update intervals, ensuring my batteries do not appear offline in the Deye cloud app.

I have a question for the more experienced users:
Is there any way to tell the inverter/BMS to stop charging the batteries once a certain SOC is reached, regardless of low load consumption and high PV generation?

The issue I am facing is that my batteries are constantly overcharged (99–100% SOC almost all day long) whenever there is abundant PV energy and my household consumption is low.

For context, I do not plan to sell energy to the grid. My priority is not so much saving money on energy bills, but rather ensuring reliable backup power for my home, as I have some critical energy consumers running continuously.

I am currently using:

• select.deye_inverter_work_mode: Zero Export to Load
• number.deye_inverter_zero_export_power: 50W
• select.deye_inverter_io_mode: Generator
• select.deye_inverter_energy_pattern: Load First

I have defined my TOU to top up the battery until it reaches 80% SOC during the day, and then gradually discharge it down to 60% SOC (to keep backup power available for emergencies).

However, I’ve noticed that on sunny days the inverter ignores my TOU settings and continues to overcharge the battery to 100%, keeping it in the 98–100% range for most of the day when household consumption is low.

I contacted Deye support and requested the latest MODBUS RTU for my inverter (I can share it if anyone is interested). I also asked whether there is a StopSOC/MaxSOC/LimitSOC register that could be used to stop charging once a certain SOC is reached. They explained that the StopSOC register has been removed, and that this behavior is considered normal, claiming it does not harm the battery. I am still unsure how healthy it is to keep the battery at 100% SOC constantly.

I have seen some users implement complex automation scenarios that adjust the inverter’s max charge/discharge current to slow down or speed up battery charging/discharging.

I was wondering if there are any other possible workarounds, perhaps by manipulating number.deye_inverter_pv_power or something similar.

Thank you in advance to anyone who can provide guidance.

Does anyone have suggestions on this topic?

[davidrapan]

Hi @stoil, did you try to lower number.inverter_battery_max_charging_current when is SOC above desired value?

[stoil]

Hi @davidrapan, tbh I have tried but I can't say how much this affected the overcharging. I guess in order to make a proper use of the number.inverter_battery_max_charging_current I would need a bit more evolved automation which can change the charging current based on forecasts, usage, etc, etc.
I found a post where a fellow user has developed and shared such automation: https://diysolarforum.com/threads/home-assistant-adaptive-battery-charging.102492/
This might work for my case.
But before jumping into the deep water I just wanted to see if there are other and more simpler ways to achieve similar effect.

[stoil]

Hi Again! Today I was finally having some good sunny hours and at the same time my house load was a little bit more predictable and controllable so I decided to experiment a little bit with the Battery Max Charging Current.
I can confirm that reducing the Battery Max Charging Current directly affects how much energy the inverter will point to the Battery, which respectively limit the PV generation as well. I saw it happening real time. When I set the Battery Max Charging Current as low as 1A, I saw that the inverter stops charging the battery when the SOC defined in the TOU is reached .

I am not sure if this is the best possible way to control the overcharging but it seems to do the job.
I guess a slightly modified version of the above mentioned automation might give you a relatively good dynamic control over the charging.