question

guitargeorge57 avatar image
guitargeorge57 asked

SmartSolar MPPT 75/10 fuse blows repeatedly

I've recently installed a new Charge Controller MPPT 75/10 to my fairly basic van system (see wiring diagram), and after a few teething troubles, succeeded in getting it all up and running (see screenshot from VictronConnect app – it was dull day). A few hours later, however, the Controller was cycling every couple of seconds between Bulk and Off states. A little exploration on this community pointed to a blown fuse in the Controller, and that seemed to be the problem.

I've now replaced the fuse four or five times, but as soon as the breaker between the Controller and the battery is closed, it blows again. I've tried disconnecting the PV panels at the breaker switch on the right, and opening the breaker between the leisure battery and the DC to DC charger. I've checked all my polarities are correct and looked for potential shorts, but everything seems in order. The fuse still blows every time I close the breaker. Everything connected to the fuse box is working.

There's a page on the Victron support site that suggests the unit may be faulty, but before I send it back, I wondered whether anyone here might shed some light on this?

Many thanks

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MPPT Controllersfuses
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wiringdiagram.png (36.1 KiB)
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6 Answers
gazza avatar image
gazza answered ·

Your diagram looks fine and if everything is wired correctly with a new battery I can’t see why you would be blowing fuses? So I agree it probably is faulty I am afraid? Clearly there is a short somewhere.

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guitargeorge57 avatar image
guitargeorge57 answered ·

Solution update for those with similar problems. The unit was indeed faulty. The supplier replaced it without question and the new on works perfectly.

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gazza avatar image
gazza answered ·

Just to be sure, did you check that the fuse was really blown (with a multimeter?). Not being rude but, but on a cloudy day it is not unusual to switch between bulk and off. What PV have you got connected? Is the battery itself in good condition?

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guitargeorge57 avatar image
guitargeorge57 answered ·

Thanks for responding, and understood about the cloudy day.

So I’ve had to replace the fuse four or five times and every time I’ve removed it I’ve checked visually to make sure that it’s definitely blown. It’s definitely blown. When the unit was working and cycling between Bulk and Off, there was an error state very briefly popping up, but it was disappearing so quickly that I couldn’t tap in to find out what it was.

Re the PVs, we have two Victron Energy Solar Panel 12V 115W Mono series 4a wired in series. Currently, though, the unit is isolated from those via the breaker switch, so it’s only connected to the battery - again through a breaker - and it’s when I close that breaker to complete the circuit that the fuse blows…with the flash that you would expect. This did not happen when it was first installed, and I haven’t changed anything about the setup.

The battery is new and currently reading 12.8V.

This is the Victron support page I referenced.

Keen to hear any further thoughts.

Thanks again.

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guitargeorge57 avatar image
guitargeorge57 answered ·

The inline link to the Victron support page seems not to have worked. Find it here: https://www.victronenergy.com/media/pg/SmartSolar_MPPT_RS/en/troubleshooting-guide---mppt.html

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davebad avatar image
davebad answered ·

That page is no longer available. If you have any of the important text please post it here.

Thanks

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