I have found 2 ways to charge 4 cell LiFePO4 with solar panels: 1 buy the correct specific LiFePO4 charger, only ones of which I know of are made by genasun. But they only go up to 34ocv input and 10 amps output. And are right about $200. 2 Take something that has the full range of charging options and set it as close to lithium as possible. I originally bought a 10 amp genasun and I am about to out grow it. I have 150 watts installed now and I am going to install over 200 watts. My charge controller choice for the 15 amp charger is the Morningstar tristar MPPT it can take up to 75ocv and are $225 all day long. To make the Morningstar tristar MPPT intended for lead acid work with LiFePO4 you have to do a few things to it. The most important thing to do is set the charge controller to the "gel battery" setting limiting voltage to 14.1 to 14.2 volts. Next disable equalization, normally turning on the "gel" setting does this, on Morningstar it does. Then disable the remote temperature compensation by installing a 10.1k Ohm resistor on the remote temperature sensor terminals. The default setting uses the built in thermistor. To disable the temperature compensation I bought a remote temperature sensor just so I could measure it's resistance at room temperature. That is where I got the 10.1k ohm number from. So you should be able to use any charge controller with a "gel" battery setting, equalization cancel setting and optional remote temperature sensor that can be tricked by installing a resistor. The main thing is you absolutely can not hit a LiFePO4 battery with equalization voltage.
