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expresslife avatar image
expresslife asked

MPPT internal breaker?

I have a question that I hope you can help with regarding some internal breaker that keeps tripping. The unit works flawlessly most of the time however, occasionally it will blink off for a second and then come right back on as if a breaker was tripped. I know this is the solar controller because our loads are fused, not on breakers, so it must be happening inside the solar controller. This happens at random and is a concern for us because it controls the loads in our RV including our fans which are the primary source of cooling for our dog and we have returned to the RV once to find the fans not on. I am also concerned because I know having solar energy coming into the controller without the controller on is not ideal, but it does not trip the breaker on the solar panels. Have you heard of this happening before or have any advice on how to start hunting down the issue? Below is our wiring diagram for reference.

MPPT Controllers
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3 Answers
Jeremy Albrecht avatar image
Jeremy Albrecht answered ·

I see 6 wires going to your MPPT in the diagram. With only four connections how is that hooked up? Do you have the wires to the batteries and the wires to your DC loads hooked up to the Battery terminals on the MPPT, effectively using it as a busbar?


Is it possible that you're overloading your batteries and their internal BMS is tripping? With no battery the MPPT will shut off. What charge settings are you using?

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expresslife avatar image expresslife commented ·

The 100/20 MPPT has 6 connections at the bottom, two for solar in, two for battery output, and two for load output. See the link below to confirm.

https://www.victronenergy.com/solar-charge-controllers/smartsolar-mppt-75-10-75-15-100-15-100-20#pd-nav-secondimage

Its also not possible that I'm overloading the batteries because this fault will occur when just the lights are on.


I fear a short circuit is the problem but I dont know how to diagnose it.

I dont have the settings available right now, but orgianlly thought it might be the load output settings. I turned that to 'always on' and it did not solve the problem.

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nebulight avatar image
nebulight answered ·

You are running all DC loads through the MPPT which is limited to 15 amps. It has built in disconnects based on voltage and load. I've never used the output before, I always take my DC loads back to the busbar. If your MPPT is close enough to your busbars, just remove them from the load output of the MPPT and place them on the busbars.

If you are using the load output to disconnect the loads based on voltage, check the load output settings in the app to see if you have them set too high.

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expresslife avatar image expresslife commented ·

Thanks for your comment. I'm using the fuse block as the bus bar for loads. Youre right about the 20amp max but there's no way I'm exceeding that. I have checked the load output settings in the app and made sure they are reasonable. This issue happens at full battery with just the lights on so that's not the problem.


I fear a short. any suggestions on how to find a short?

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expresslife avatar image expresslife expresslife commented ·

Could it be the fridge kicking on and momentarily spiking past 20amps? Even though the fridge is fused for 15amps the solar controller could see a spike past 20 if the lights are on and maybe the water pump.

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nebulight avatar image nebulight expresslife commented ·

I just read the manual and I think the max is 15 amps not 20. Easy fix is to move the DC loads from the Load output the the Busbar for the battery to test. If the issue goes away, it's the load output.

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expresslife avatar image expresslife nebulight commented ·

Thank you. I'm going to try this based on your and mrseas suggestions

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mrseas avatar image
mrseas answered ·

Using the "output" terminals for your "loads" is not the intent of the "load" connections on the MPPT. The function of the "loads" output is to control relays for various functions not to power all of you 12vdc loads. You would be better served with less possible issues to move the leads you have connected to the MPPT loads and connect to your battery(s). You will possibly damage the MPPT as presently connected.

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expresslife avatar image expresslife commented ·

Can you provide evidence to your claim that I should not be putting all 12VDC loads though the solar controller?

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