Lifepo4 SOC based charging

[Csimmer]

Hi, I am using the SOC relay in a Victron BMV 700 to control a contactor which switches the pv panels to my chargers. This way I can charge my batteries with a higher voltage setting and have it stop at say 80% SOC to increase my battery lifespan. This works very well. The only issue is that I need to be aware of is the BMV drifting as it never gets close to 100% SOC to reset. I check my battery voltage and BMV SOC in the mornings after my batteries have not seen any large charging or discharging events and compare it to the voltage/SOC chart I found on this forum somewhere. My load is never zero so my voltage will be not a true resting voltage because the fridge, freezer and standby loads are about 500w (I have 16s 2p 280ah). From the SOC/V table I have interpolated a voltage for every 1% SOC and made this spreadsheet to keep a check on my BMV drift. I use a google form to enter the readings via my phone.
Any criticisms or advice?

SOC monitor (Responses)

Form responses 1 Timestamp,Resting Voltage (0- 300w load),SOC,Date,Current draw ,Nearest table voltage,Nearest SOC,delta SOC (read-table),delta V 28/02/2021 09:40:33,53.16,80.5,21/01/2021,53.16,79,1.50,0.00 28/02/2021 09:41:06,52.35,58.8,22/01/2021,52.36,58,0.80,-0.01 28/02/2021 09:41:58,53.24,78.3

docs.google.com

 

[toms]

I have tried many different settings to try to get my BMV to accurately reflect my LiFePO4 pack SOC. After a few months of not fully charging it has always drifted off (sometimes by up to 20%)

I’d love to know if you find settings that work out for you long term.

 

[Csimmer]

I have tried many different settings to try to get my BMV to accurately reflect my LiFePO4 pack SOC. After a few months of not fully charging it has always drifted off (sometimes by up to 20%)

I’d love to know if you find settings that work out for you long term.

If you have a look at the spreadsheet you'll see my presumed SOC is fairly consistent over 2 months so far, I am recording these readings in view to fine tune the BMV settings if they start to deviate.