Controller State of Charge (SOC)

Evening all, tech tip time 🙂

The controller in the pic is a PWM, in the image it displays State of Charge (SOC) in the bottom left corner. If you have one of these controllers and it is displaying SOC, have a look at the bottom of the controller and see how many cables are connected, there will be six terminals, if only 4 are being used, the controller is in the wrong mode and will be significantly undercharging your battery. The reason this happens, is that SOC mode can ONLY be used where ALL of your loads are connected to the additional two terminals on the right of the controller. This does not only affect Fangpusun, any controller that looks like this one and is showing “SOC”.

It is a simple fix, you can do yourself. If you use the up/down button and toggle through until you see the battery voltage display, then press and hold the right button for 5 seconds or until the display changes, the screen should show “SOC” now press the up/down button (usually one press) until you see “VOL” now press the right button again and the controller will revert to its usual state and will now show “VOL” in the bottom left and you will no longer see the SOC % display.

SOC State of Charge on a Controller
The controller is now looking at the battery to determine the right charge profile as opposed to looking at the load terminals. This is important because in SOC mode the controller is looking at the load terminals ,to see how hard the battery is working, seeing no load it is assuming the battery is not working and is in a better state than it actually is, thus undercharging the battery.

In “VOL” (voltage) mode, the controller is now looking at the battery to determine the right charge profile.

“One further comment, if you have one of these controllers and your system is working fine, all good!

If you fell like it is not keeping up, by changing to an MPPT controller you will get you a minimum 30% increase in charge efficiency without doing anything else to your system.”