LifePo4 battery reading 53.29v at 100% charge?

[Andy_Knowles]

Hi all,

I have a 120ah LIfePo4 battery (48v) it's been working perfect since I got it a about 7-8 months ago,
I've noticed the voltage being a little low a few times, I checked this afternoon and the battery is fully charged - 100% but sitting at 53.29v! - that's surely not right.
The battery case says 58.4v is maximum charge.

This is connected via a Growatt 5000es hybrid inverter, and set up as instructed by the seller.

I'm not sure what i need to do to push the voltage back up to the right amount?
I know there are a lot of 5000es users out there, so does anyone know what to do?

 

[sunshine_eggo]

LFP is like lead acid in that it needs to be charged at elevated voltage to achieve full charge, so this may not be completely out of order.

Are you able to see individual cell voltages?
Have you observed the battery charging to higher voltages?

 

[TomC4306]

The SOC indicator is a secondary gauge. It's a calculated value, not a direct measurement.
So, even though this value says 100%, the battery might not be at 100%.
53.29v is 3.33 per cell.
Possibly just under float. Near full.
What charge voltage and absorption time is set in your Growatt?
Open the manual, go to the settings section, find out how you read these settings from the inverter, discover which settings are for absorption/bulk charge voltage and which is for absorption time. Also perhaps check to see what float voltage is set at.
Report back.

 

[SeaGal]

I've noticed the voltage being a little low a few times, I checked this afternoon and the battery is fully charged - 100% but sitting at 53.29v! - that's surely not right.
The battery case says 58.4v is maximum charge.

The issue is likely that the battery's BMS has 'drifted' its measure of SOC. BMS's typically measure current in and out via an internal shunt resistor, but unless it is charged fully or discharged fully, will not "reset" to a correct SOC value. Hence, over time, it will likely drift from the real value.

Are you able to see individual cell voltages?

The screen shot shows min and max cell voltages of around 3.33V, so in my books that is probably around 80% SOC if there is no load/charge current.

My JBD does the same, gradual drift down in SOC reading vs. actual SOC unless the cells hit a min or max. But I am able to manually have it do a reset (albeit based on cell voltage) to re-estimate the real SOC.

I have a Solis, not a Growatt, but I am guessing that the inverter will not charge the battery once the battery reports 100% SOC, so you end up in a not-fully-charged cycle.

Suggestion would be to see if a reboot of the battery fixes it (i.e. it re-calculates 80-something percent) or whether there are some other console / menu buttons you can press to have it do a reset of SOC. Once the battery reports a more accurate value, then your inverter should start re-charging the battery.

Edited to add; @TomC4306 just beat me to some of the same points!

 

[DIYrich]

What charge voltage is the Inverter set at? My system charges at 55.0v to 54.5v (BMS resets to 100% SOC). Then it turns off. The cells will then settle to around 53.3v with no charge voltage being applied (BMS stays at 100% SOC).

 

[Andy_Knowles]

Turns out as lots of you have said - it's about right.
My Growatt is set up to use protocol 051 (which is correct for the battery) this means i don't manually set the charge voltage etc... it's all in that protocol.

Thankyou for the responses - i shall stop being paranoid now!