Help with repairing charge controller

Hello guys

I have a year old chinese EPSolar PWM charge controller (50 amps 48 volts "VS5048N") that I use to charge my 200 Ah battery bank from a 2KW solar array, and after a few days of continuous rains a little water seems to have found its way into it and now its not functioning properly. It shows the PV array voltage at night, even, and it is rather the battery voltage. While the battery voltage it shows is in the range of 0.1 to 13.6. So it switches to 12 volts mode (thinking that my 48 v battery is 12 v) and I can hear the PWM noise so the PWM still functions at least. Its red fault indicator light blinks and the screen reads "MOS-I short". Whatever charging it does provide now is meager.

I checked inside to find a large 100V 470mF capacitor and two smaller ones. There were lines of salt residue on the PCB which I removed. The large cap seemed to have leaked so I changed it. However the unit is still not functioning. I can not find any signs of burnt mosfets which I checked with an ohmmeter albeit without unsoldering them all first. Thing is that I have no clue now what may be wrong. If I could get any hints on where to look I could attempt repairs myself instead of paying for professional help or a new unit and getting robbed. So if anyone has any clues at all, please share.

P.S.: I also have a 50 amp 24 volt unit. Perhaps I could modify it and make it work with 48 volts battery system or use it somehow?


  • BB.BB. Super Moderators, Administrators Posts: 32,747 admin
    Re: Help with repairing charge controller

    It can be difficult to repair power electronics... If a FET goes bad, it frequently takes out the drive circuit too--So you are left trying to figure out the circuitry in that area too.

    You can try washing the whole electronics board/components (less anything that is not water proof), with mild soap and water and rise with distilled water--Then let it dry--If you got salts on the board, the washing may clean that up.

    In general, your battery bank is probably pretty expensive, if not more costly than a new charge controller... You might be better off replacing the controller with a new one--And hopefully the battery bank is not damaged by a bad/flaky charge controller.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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