I have a Victron mppt controller and have noticed that adding solar panels does not really increase the current going into the batteries (as measured by a victron battery monitor).
The issue is that when I am at anchor for a day or two, the battery will go down to around 80% SOC and the amount of current going into the batteries appears to be about .45 amps at most. It does not matter whether I add panels in parallel or in series. My understanding of the Victron controller is that I should be in the absorption phase. Perhaps this is why the amount of current is this low? However, when I load goes on (e.g., I flip on the refrigerator) the batteries are discharging and I don’t see a big difference between having the solar connected or not. Is this because the controller only pays attention to the voltage of the battery and does not respond to a load being added? Is there a tweak that allows the controller to respond to additional loads?
As you can tell from my post, my understanding of these things is a bit shaky and any insight or suggestions would be helpful.
@ksailor To get some targetted help let us know what solar controller type and model and what type and voltage of batteries you have. If you have bluetooth on the controller some screenshots from the VictronConnect app for settings and performance ate useful.
One reason for very low charging that we commonly see is a poor connection somewhere between the panels and the controller or controller and battery causing high resistance and voltage drop. Similarly poor isolators, fuses or breakers. Check all your connections and if you have a multimeter use that to check the voltage if you know what you are doing.
Thanks. The controller is the Victron MPPT 75/15 but it is a bit older and does not have bluetooth. The battery monitor is the Victron BMV 602. The batteries are two six volt 236 ah batteries wired in series.
I checked the voltage at the posts on the MPPT controller and saw 16 to 18 volts.
Was the 16 to 18V on the panel terminals or battery terminals. When the unit is trying to charge measure the voltage on the batteries and then the MPPT battery terminals, they should be the same or at most 0.3V different. If the battery says for example 12.7V and the MPPT 14.4V then you have a poor connection between the MPPT and battery.
The voltage is nearly identical when measured at the battery posts and at the posts for the battery terminals
If the MPPT was on absorption at the time you measured it that suggests you have a good connection from the MPPT to the battery. Have you checked the fuse on the bottom of the unit, the orange thing in the bottom left of the picture
The other thing is that to start charging the voltage needs to be 5V above your battery, so around 18V. Once charging starts then the panel voltage needs to be 1V above the battery, i.e. about 15V.