What do you think SOC is charging to 3.45v

[Padzb]

I have 4 x 300Ah CATL LiFePo4 in series on a boat charging from 300w solar. 2 x victron smartsolar regulators & a victron smartshunt. regulators read to voltage from the smartshunt & are set to bulk - 13.9v (3.475v per cell) then 'float' - 13.37v (3.3425v per cell). No absorption time.
A raspberry pi reads & logs data from the smartshunt.
This seems to work fine, but I don't believe the smartshunt SOC, it was set months ago & good chance it has drifted. So what SOC do you think the cells have got to when voltage gets up to 13.9v? Shunt says about 60%.
This shows it quite well with the regulators going from bulk to float at just under 14v (3.5v per cell)



SOC graph shows just under 58%. Not sure I believe that..??


'Float' seems to work OK, just keeps on top of house loads, you can see the fridge cycling quite clearly


So what do you think the SOC might be when it gets into the upper knee? Or any other comments? Actually not too bothered what it is, seems well within safe limits & there's plenty capacity so never gets discharged too much. It works! ?

What was interesting was absorption, tried 1h absorption but nothing much went in to the battery after leaving bulk keeping voltage up so now go straight to 'float' (not really the same as lead acid float)


Thanks ?

Edit: Just set absorption voltage to 14.2v (3.55v) just for today, thinking of resetting capacity to 100% when it gets there & live with that. Comments? ?

 

[sunsurfer]

I'm betting absorption time with slightly higher volts will likely get you past the 60%. I'm assuming your goal is 80%? The push voltage is always a bit higher then the cells till the absorption reaches very low current, than they are closer to each other in actuality. Of course, this precludes any internal leveling out within the cells.

 

[Padzb]

I'm betting absorption time with slightly higher volts will likely get you past the 60%. I'm assuming your goal is 80%? The push voltage is always a bit higher then the cells till the absorption reaches very low current, than they are closer to each other in actuality. Of course, this precludes any internal leveling out within the cells.

The 60% the shunt says is almost certainly wrong, it's not been reset for months now. The question was what do folks think the SOC might be? Just did another cycle up to 14.2v / 3,55v per cell, only took a few minutes more the 13.8v & next to no increase in SOC. For now I'll call that 95% and see how it goes.


Then maybe terminate charging at 13.7v, no need for the last bit of capacity.

 

[TomC4306]

You need to tell the shunt what is 100%. And 100% is anything above 3.45 for 60 minutes.

I don't have a shunt but check the settings. I'm pretty sure victron can be adjusted for when it resets to 100%.

 

[Padzb]

You need to tell the shunt what is 100%. And 100% is anything above 3.45 for 60 minutes.

I don't have a shunt but check the settings. I'm pretty sure victron can be adjusted for when it resets to 100%.

Yep, just done that. Except no point keeping volts at 3.45v per cell, nothing more goes into the battery. Reset will be manual from now on maybe once a week, no point pushing it all the way. Might one day tell the regulators to float @ 80%.