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urbanoverlanding avatar image
urbanoverlanding asked

MPPT tripping breakers

I've had my system installed for ovear a year with no issues, and suddenly this started happening. (no changes to system)

So, I've got a 290 watt single panel the goes to a 30amp circuit breaker, then to my victron 100/20 mppt. To another 30amp breaker and then to a bus bar. Which goes out to the battery, fuse panel, and inverter, all of which also have breakers.


So a week ago i get in and pull up my stats and notice no solar coming in. I look and the breaker between the panel and the mppt had tripped. Well it's in a not so great place, and I thought i may have bumped it. So I reset it and everything was good until the following afternoon.

Now the breaker between the mppt and bus var tripped. I inspect all of my wiring and can find nothing wrong. I reset the breaker and move wires etc as much as possible to see if i can get it to trip. Nothing. Again works great until the following afternoon!

Is m charge controller at fault? Any ideas? My battery died due to this. And as much as I would love a valid excuse to go lithoumm, I just want my fridge to stay running.

Sorry for the long post! Thanka if you made it this far!

Solar Panelfusesmppt charging
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4 Answers
JohnC avatar image
JohnC answered ·

Hi @UrbanOverlanding

I can't help but think you may be using those little lever/button breakers. If that's so, then that will be your issue. There may be better brands, but the cheapies do exactly what you describe.

They get hot internally, and can only dissipate internal heat down the connecting wires. And you can test that, they'll get hot. And trip.

I may be off the mark here, but maybe you could confirm..

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Are you using breakers that are designed and rated for DC?

Something like this? http://www.noark-electric.eu/en/products/Installation_devices/DC_Miniature_Circuit_Breakers_Ex9BD

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urbanoverlanding avatar image
urbanoverlanding answered ·

I am using blue sea dc breakers.

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JohnC avatar image JohnC ♦ commented ·

Better quality, and on the front of those they should mention 'thermal'. And that's what trips them.

You could try running bigger wires to and from them (at least for the first 10-20 cm) to help remove the accumulated heat. Spare the shrinkwrap to test.

I agree they're very handy devices, but the only ones I've had success with were rated double the current they were likely to see. Then I lifted the wire size to suit the breaker rating.




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urbanoverlanding avatar image
urbanoverlanding answered ·

@Johnc I've been running this for over a year though. Also I've got the best of the units you can buy. Any way to actually test this?

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JohnC avatar image JohnC ♦ commented ·

Feel for heat. I understand you may be looking deeper for a fault in the mppt, but a 290W panel can't provide enough A to trip a 30A breaker. Perhaps some sort of catastrophic-type reverse current fault from the batts might, but then you say everything works mostly.

It'll be the breakers, that type has been discussed here way-back, and no poster praised them. And if you look back at my first post, the symptoms were there. And I even picked the type.. that's what they do.

Heat-sink the terminals, bigger wire, bypass them, get bigger ones, whatever. Or go on bleeding from spurious trips.

I have a couple of similar at home (up to 150A), long removed from service and now in the spares bin. Might use them one day just as isolators on tiny circuits. Handy for that.

But I do sympathize. I've been there too, and seen others do the same.

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