usability of lithium with lead acid charge profiles ?

WoodsieLord

Solar Enthusiast
Joined
Oct 4, 2019
Messages
122
expensive and custom built LiFePO4 batteries are SLOWLY becoming available here in Argentina. Before I get too carried on putting my sky mask grabbing the rolling pin and heading to the bank asking for donations...

I have a cheap MPP solar clone inverter that is not compatible with lithium. Available charge profiles are AGM, FLA or USER. The later one allows you to set
- BULK charge voltage
- FLOAT charge voltage
- low voltage disconnect
- Enable or disable Equalization (and it's respective parameters, if enabled)

I also have an EPEVER MPPT CC that features lithium (if I recall correctly) that I'm not currently using.

I've read the LiFePO4 charging profile sticky and the BULK charge is not mentioned ( Absorption is used ).
Should I forget about lithium with the cheap MPP clone? What would you do?
Thanks!
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Joined
Oct 29, 2019
Messages
5,408
Location
Rural NE Ontario Canada
You'll have no problem with the MPP unit and LFP. The biggest issue with Lithium" is not LFP but NMC, NCA and such because their voltage ranges are not "typical" with regards to being close to FLA voltage ranges.
* ABSORB is short duration.
* Equalize is either set to OFF or to Absorb Voltage for as short a period as possible.

Here are the Settings I use with my Midnite Solar Classic 200 and similarly set for the Samlex EVO Inverter/Charger
All equipment MUST BE Voltage Corrected & Calibrated (VERY IMPORTANT) see link in my signature on how to do it.
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 28.2 for 15 minutes (3.525vpc) (some call this boost)
Equalize: OFF
Float 27.9V (3.4875vpc)
MIn Volts: 22.0 (2.750vpc)
Max Volts: 28.7 (3.5875vpc)
Rebulk Voltage: 27.7 (3.4625vpc)
End Amps: 14A (*1)

(*1): End Amps is calculated from the Highest AH Battery Pack in a Bank. IE: 200AH X 0.05 = 10A 280AH X 0.05 = 14A.
NB: Victron Forum discussion says EndAmps = TailCurrent
This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are on average between 3.475-3.500. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off.

** Coulumbic Efficiency for LFP is 99%
 

DLTooley

Solar Enthusiast
Joined
Jan 12, 2020
Messages
129
The User profile on your cheap controller will allow you to set those parameters to be compatible with LiFePo4. The biggest issue is likely temperature cut-offs, I don't recall whether the Epever's have those. Keeping the batteries in a continuously temperature controlled living space is the easiest of many solutions.
 
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