Charge Controller Settings

[Alpine_Junky]

Looking to understand how to set up charge controller -

DIY Battery: LF280K - 16 cell configured for 48V system with Overkill BMS - 18650 Grade A cells

Charge Controllers - 2 Midnight Classic 200's - both running 2 strings of 6 panels rated at 380w each panel (12 panels x 380 = 4,560 watts). Has shunt and whizbang in master controller. One set of panels gets morning sun and the other afternoon. Northern location with crappy aspect...

Inverter is a Schneider 4048 - expect generator run time in winter - paired with Harbor Freight inverter super quiet 9500 genny. Was thinking of adding a better charger down the line if it makes sense -- still sorting through optimal charge rates for gen assisted charging to balance gen run time and battery life.

Understanding Will's settings below - I can easily set the charge controller to these values.

The curve ball that I can't quite figure out how to set up the charge controller. I was able to locate this documentation but its somewhat generic (I believe improperly refers to the BMS doing the charging) https://www.midniteftp.com/support/kb/faq.php?id=75


48V 16S LiFePO4 Battery w/ BMS

• Absorption: 58V
• Float: 54.4V
• Inverter Cut-off: 42.8V-48V

5,000+ Charge Cycle Absorption Recommendation
If you want your LiFePO4 cells to last a long time, you can set your absorption to Victron's custom LiFePO4 charge profile recommendation:

• 48V Battery: 56.4V

You can pull full capacity with the absorption figures above, but the charge rate will be reduced at high SOC.

Float should be 13.6V/27.2V/54.4V

Low voltage disconnect should be 12V/24V/48V

 

[BentleyJ]

Absorption at 56.0V to 56.4V (3.50V to 3.525V per cell) is adequate to fully charge the battery. Its just not necessary or desirable to "Blast" the battery with 58V (3.625V per cell) What really doesn't make any sense is many BMS's have default HV Cut Out settings of 3.60V to 3.65V yet we keep seeing these super high absorption voltage recommendations. It almost guarantees the BMS will shut down during a charge cycle.

As far as float, it depends.
If the system is primarily used for back-up then float is not necessary, in fact may be detrimental. The battery should be topped up then charging should stop. Repeat every few days depending on the stand by load and what average SoC one desires.

In a situation where the inverter & battery are being used in a self consumption mode then it makes sense to let the SCC remain in float to provide power to the loads while PV is available. Float at 53.6V to 54.0V would be a very easy on the battery.