MPPT 100/20 not charging

Q&A and troubleshooting
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1

Hi all, never had an issue with Victron gear in the past so created an account to see if I am doing something wrong.

I just got a MPPT 100/20, hooked it up to a battery updated the app software and the charger firmware, pulled out the battery protection bridging plug and put an engel on as load, all good. I plugged a 200w solar panel in and expected it to start charging but it did not. The voltage on the battery was pretty good, 13.4 or so when I started so so thought I would leave it a while.

Anyway the solar panel is putting out 19V if I disconnect the wires from the terminal on the MPPT 100/20, however when I connect it to the terminal on the charger the voltage drops to around 12.1 - 12.4 V measured at the terminals. When the solar panel is not connected the voltage on the screw terminals is 0V. Battery was about 12.4 operating after a while.

I’ll run the freezer all night to get the voltage down a bit and will try again in the morning. I didn’t check to see what the solar panel terminal voltage was with the solar panel connected but not in the sun, however I would have though the voltage at the terminal would be the solar input voltage, not a voltage about the same as the battery voltage.

Any suggestions or may I have a questionable unit, I’ll try again tomorrow with a lower battery voltage.

Thanks, Brad

2

I actually just found another thread that indicates that I may need to put my panels in series, or get a PWM unit as 19v open circuit may not be enough. Does that sound correct for these units?

3

PV voltage at the MPPT has to be 5V above battery voltage at the MPPT for charging to start.

4

yep, you are right. I changed the portable 2x100w panels to series and it works now. I understand the must be more than 5V to charge, but was surprised at the no load V dropping from 19 to 12 odd volts.

Thank you kindly for your response and support!

Brad