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sailboattn avatar image
sailboattn asked

SmartSolar MPPT 100/20 turning the load "On" then "Off" then back "On".

I purchased a Victron SmartSolar MPPT 100/20 Charge Controller. I am having a problem with the charge controller cycling the load "On" then "Off" then back "On".


Description of failure:

1. The charge controller will show that the load is set to "On".

2. A 12v fan is connected that draws a max of 9W of power or a car cell phone charger is plugged in (without the phone connected or charging)

3. The charger controller will show that the load is turned to "Off"

4. Have a pause for 1 to 2 seconds

5. The load will then be turned to "On"


Notes: The charge controller never shows a voltage below 12.6 volts from the battery so I know that it is not pulling a large load from the battery.


I don't see how a 12v phone charger without a phone connected could be tripping the 20A capacity of the controller.

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Pat avatar image Pat commented ·
What does it mean the load is turned off and on? If you have a light connected to the battery that is charged or being charged, does the light go on and off? I am confused with the words ... I read in my victron mppt solar controller there is no switch to turn it (the controller) on or off as per say, to turn it off you remove the solar and power wires.
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2 Answers
ripper avatar image
ripper answered ·

Probably it has a capacitor on the inlet. The inrush current to charge this is too high and will be detected. Therefor it shuts off. While its shut off, the capacitor discharges so the next attempt will be unsuccessful too. The detection is a bit on the whingey side, somebody here showed it with an oscilloscope.

For a trial use a little resistor with 1 or two ohm and 5W capacity and see what happens. It might get too hat during operation, so you might end up with needing to buy another phonecharger anyways.

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adev avatar image adev commented ·

Aye that’s most likely the issue. My macbook charger (12v) and my 12v USB-C chargers both cause the load terminals to cut out momentarily but it then comes back on and operates as normal.

I only had one USB charger that made it cycle like that repeatedly and it turned out to be a faulty charger.

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sailboattn avatar image sailboattn commented ·

I don't think it is detecting a rush of current from a capacitor because if I go under "Trend" and look at the "Live Amp Load" it nevers gets over 0.2A.

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adev avatar image adev sailboattn commented ·

The spike is very fast, too fast for it to be seen under the trends graph as that only has a 1 second refresh rate.

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sailboattn avatar image sailboattn adev commented ·

So using my SmartSolar 100/20 I switched on the load and measured the current max current going through the "Load Terminal", it necer exceeded 0.45A. I then decided to switch in a spare SmartSolar 75/10 and my problem went away. I think my 100/20 is defective.

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boxerbob avatar image
boxerbob answered ·

I am having the same thing happen with my 100/20.

It operates normally with low draw appliances like the led lights, but the cut off and restart happens with the ceiling fans and the fridge. However once the initial cut off has happened, normal operation resumes


Were you confident the controller was faulty?

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tomvacek avatar image tomvacek commented ·

I am having a very similar issue with my 100/20 after the recent firmware update, posted about it here: https://community.victronenergy.com/questions/65832/mppt-10020-turning-load-onoff-every-second.html

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