Lithium charging Cut-off current 0.033C

[BrissyBrew]

Can somebody please help me with this, appears to be a big difference of opinions regarding charging.


Just trying to reconcile in info in these two web pages:
Charge currents cut off for low <0.05C: Marine lithium batteries in operation | Nordkyn Design.
vs
https://marinehowto.com/lifepo4-batteries-on-boats/

I am about to install a DIY 400AH Winston (8S cell 24V) system. Charging devices:
Victron 100/50 Solar Charge controller (PV array 1300W)
Victron 3000/24v 70Amp inverter charger.
30A DC to DC charger (enerdrive DC to DC charger for the alternator)

First of all I read about low current 0.05C - 0.033% (for me looking at 20A or greater for a single cell or 8S). Which means my original idea for initial top balancing of using a 10Amp CV/CC power supply is out, even on a single cell (although two charges in parallel might do it) but a paralleled bank is totally out it would need 160Amp charger. I did see if I could hire one nope not in Brisbane.

So for initial top balance
Charge to 3.35V stop the charging process, let the cells rest for a few hours, and measure the terminal voltage. When the resting open-circuit cell voltage reaches 3.35 volts you are done. Stop there!. Or just change to voltage as per marine how to instructions.

I am thinking of using 70A charger in the multiplus to do the initial bulk charge at 8S terminate it lower then try topping up the cells individually. I just realise I am leaving cells at 100% SOC for a long time in this process which is a no no but like what's going to happen when I normally have them fully changer.

For normal operation
I can program the changers (also have a programable BMS for cell / secondary protection)
-Solar 1300W PV array but that is max in theory only, stop on voltage with no absorption? In theory sometimes it could be putting out more 20A, eg 50A that would I be better treating it is a larger current and have some absorption time (lower voltage)

30A DC to DC charger voltage with absorption time (at a lower voltage?)

Victron 70A inverter/charger absorption time (at a lower voltage?)

Your recommendations would be appreciated. I want to protect my investment in the battery bank.

Originally I thought I could do it by having voltage based termination and zero absorption rate, how I see a think to memory issues in lithium batteries. Totally confused.


I was thinking of setting the BMS cell protection to 3.55VPC for HV relay 2.8VPC for LV relay. Setting charging voltage for the pack slightly lower. Just not sure if I should put some absorption at lower voltage on my changing devices.