SOC fluctuating wildly

[simonbuerger]

2 5.1kwh Revov batteries. It's currently set at 50% minimum overnight. This morning it did this where the SOC just dropped instantly from 50~ to 20 repeatedly and then eventually down to 5.

The batteries are less than a year old and I never let SOC go below 40ish. Deye 8kva inverter.

Is it a calibration thing or are the batteries giving up?

Appreciate any advice!

 

[Mzezman]

Probably a calibration thing. When was the last time they got to 100% and stayed there for a while to balance?

 

[SauRoNZA]

Set your reserve to 100% and just leave it for a day.

Problem should go away.

 

[simonbuerger]

Probably a calibration thing. When was the last time they got to 100% and stayed there for a while to balance?

Yesterday for a couple of hours



Should I just force it to charge from the grid today and give it more time at 100%? How long would you recommend?

 

[simonbuerger]

Set your reserve to 100% and just leave it for a day.

Problem should go away.

Thank you, will try this

 

[AfricanTech]

View attachment 1700479

2 5.1kwh Revov batteries. It's currently set at 50% minimum overnight. This morning it did this where the SOC just dropped instantly from 50~ to 20 repeatedly and then eventually down to 5.

The batteries are less than a year old and I never let SOC go below 40ish. Deye 8kva inverter.

Is it a calibration thing or are the batteries giving up?

Appreciate any advice!

My brother had a similar issue with a Hubble AM2 - eventually got the installer to take it away - they didn't find anything wrong but updated the firmware and he hasn't had any issues since.

 

[leon.davibe]

where does solarman get the soc
battery coms or voltage estimation

how low is your overnight base load
sometimes the bms calculates soc incorrect if the amps are too low so you get drift in what the bms thinks the soc is vs reality

then when it bumps up against certain voltages at the top and bottom it recalibrates

is there any load changes that time of the morning
if the battery uses voltage to estimate soc load changes may cause voltage to dip and thus the estimate

what is the voltage when it does this close to cut-off voltage?
if it is then the bms miscalculates the soc and has to be jerked back to reality

most likely nothing wrong
edit apart from what you thought was 50% isn't actually 50%

can check by having a higher load (bms tends to be more accurate at higher load)
then see if it behaves the same way

 

[leon.davibe]

another thing you could do is try and get stats per battery

another possible scenario

normally the battery coms of the master calculates the SOC by combining the SOC from both batteries
so what happens is one battery is at just about shutdown voltage

the soc thus drops down to 20% avg of both batteries
the one shuts down the master then calculates the soc based on only its own figures lets say it is 50% thus jumps to 50%
the second one accepts charge from master thus recovers and starts up contributing a low SOC thus the avg drops to 20% again until it shuts down then the soc of the master is displayed this cycle continues until the master has drained too hence the jump up and down until it is drawn down to empty

how is your battery daisy chained ie cable lentgh from battery to inverter is the cables exactly the same length
if one has a shorter distance it has less voltage drop and thus supplies more of the load and why the 2 drift appart