Is this normal for the BMS ? (2400AC+)

ZenUser4kV9s1m

Hey guys,

So I own a 2400AC+ with 2 extra batteries, they are less than 2 months old, they run the latest 1.0.3 firmware and last time I loaded by batteries to 100% was the 8th may, so not so long ago.

I manage everything with home assistant.
Basically during the day (one hour after sunrise up to one hour before sundown) I adjust the input value of the 2400AC+ every 10 seconds with MQTT to make the battery input value match the power output from my network (the idea is to catch the extra power produced by my solar panels).
One hour before sundown I switch to output mode and then I adjust the output value to what my house draws in power with a max value of 600W (to prevent useless spikes on the battery when the dishwasher heats water for example).

I normally unload my batteries to 15% and load them to 85%, so nothing too aggressive.

Today we had a sunny day and I saw that the loading speed from the battery was quite slow while being at only 70% capacity. Since I know that the load speed lowers when reaching 100%, I changed manually the max value for the battery from 85% to 100% and it reached 100% in no time (it went from 70% to 72% to 100% basically).

I know that the BMS needs a monthly calibration, but is it normal that it is so bad ? We are talking about a 30% error in less than 2 weeks here...

I checked the load % for each battery and they all went from 72 to 100% in a single minute, so it's clearly the BMS that is hallucinating.

What are your thoughts on this ?

Surfer1264(2nd)

ZenUser4kV9s1m loaded by batteries to 100% was the 8th may, so

Last time at 8th may……more than 12 days are ages ……? Really
And you are wondering WHY?

I don’t have any question.

This behaviour is normal for Zendure accus ……from 70% to 100 can happen YES

ZenUser4kV9s1m

Je prends les réponses en français aussi, si mon problème vous inspire 🙂

zzZ

No error. This behavior is normal for Zendure batteries and others.

The SoC is only calculated by the BMS. Small loading or discharging amounts are not always recognized by the BMS.

No panic.

F.e. Growatt Noah 2000

It is better to use 15% - 100% every day.

Surfer1264(2nd)

Don’t trust your Soc after more than three days

If you use Home Assistent you could have seen this behaviour long time ago if you look at the cell voltage of your batteries. That is the only real truth.

ZenUser4kV9s1m

Well I do have those batteries for less than 2 month, so it's not like I'm experienced with this. But ok, fair enough if this is normal.

Thanks for the tip regarding cell voltage, so for all I see in the history, as soon an I am above 3.4V I should consider that the battery is full enough or something, good to know !

zzZ

There is no need to limit your system to 3.4v or 80%. Always load to 100% and 3.55v-3.65 for correct calibration.

ZenUser4kV9s1m

Isn't that not ideal for the battery life in the long run?

I mean I could completely automate the load and discharge with the cell voltage indicator instead of the inaccurate load % provided by the bms

zzZ

ZenUser4kV9s1m No, the battery can withstand that. The battery must only not be stored with 100% charge for months.