How effective is the Sterling Pro Charge Ultra for LiFePO4 batteries? It seems that in bulk and float, it uses the same voltage of 13.8V and in maintenance it still holds at 13.2v. My understanding is that they like to charge then shut off. Is there a better charger for these batteries?
You don't mention which LFP batteries you are using? I will give you the same answer I did the other day....
The ProCharge Ultra is a great algorithm for lead acid, not very good for LiFePO4. The longer the bulk stage the longer the absorption stage will be. LA batteries loves this. LiFePO4 is basically all bulk which means the charger will calculate a very long absorption on every cycle, and over-absorbing is not the best choice for LFP.
If you insist on using one for LFP I would suggest using the custom setting and programming it for a max of 13.6V then drop below that for float to your desired "storage" SoC. We know of at least one major LFP battery maker who actually disallows the use of these chargers with their LFP batteries for the exact reasons I've laid out above. If you program it so the battery is only getting to 3.4VPC (3.4VPC X 4 Cells = 13.6V) then it
could work.
This could also be problematic, especially with drop-in batteries, where you may have hundreds of cells with unknown capacities and internal resistances that actually may need to get to 14.4V to 14.6V to top-balance for 20 or so minutes each cycle. Unless you have another charge source that can be programmed to do this, you may find out a year or two down the road that your batteries are too far out of balance for the internal mA level shunt-balancers to correct.
Oh, and DO NOT use the supplied temp sensor with LFP!
The other issue with this charger is the lack of dedicated voltage sensing. This is not insurmountable, with close proximity and large gauge wires, but LFP is very sensitive to charge voltage and the window is narrow.
The Victron Skylla IP44 (60A) is considerably more programmable as are their inverter chargers such as the MultiPlus Series.