I have a 20 amp charge controller, 2 12v lifepo4 batteries in series, and a 200 amp 24v solar panel and my batteries won’t charge above 26.8v. and once I disconnect the panels the voltage drops to about 26.5. I have the absorption voltage at 27.6 and the charge controller is showing 30.2 volts and 170w but the battery voltage won’t budge higher, is this normal? I would think if the batteries need higher voltage to fully charge then the charge controller would be able to drop the amps to increase the volts but it won’t go much higher than 30. Is there a setting to get the batteries to 27.6v, is this ok and normal? Thanks
I think your absorption voltage is too low. You should be charging at around 3.6V per cell depending on what the battery manufacturer recommends. That should be over 28V in your case. The 30.2 V you see on your screen is the panel side. Its what the controller is receiving from the panel not the charging voltage. The 26.79V is what the controller is charging the batteries at.
Raise your absorption to 28.2V and see what happens.
Of course makes sure your cabling and connections are all good too while your at it. I see more problems with that than anything else.
You will not see higher battery voltage until your batteries are close to 100%
look at the docu of the solar controller: the voltage on pv side has to be 5 volts higher than the battery absoption voltage. That will be your problem.
I was thinking this may be the issue which is why I was wondering why the charge controller can’t raise the voltage and lower the amps to top off the batteries. I was hoping there may be a setting or something. It almost seems the solar panel voltage has to be higher than the battery voltage to allow for that variance through full charge, 24v panel with a 12v battery for example.
To be clear the panel only has to be 5 volts higher for the MPPT to recognize the charging source and come on. Then it will charge at any sufficient voltage. If it is showing “bulk” like in the posted picture, you are charging.
This is true but will not happen if your charging voltage is not set properly.
Your absorption voltage is still too low.
I did increase the absorption to 28.2 from 27.6 and it seemed to push a little more into the battery. The amount the batteries are able to absorb I think starts to slow as the battery voltage gets nearer to the panel voltage, at about 26.8v the absorption rate decreases. Going to give it a couple days and see how close to the absorption voltage setting I can get.
