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kahlistrophic asked

Smartsolar MPPT 100/50 suddenly stops charging, updated recently to 1.64

Smartsolar MPPT 100/50 connected in a system with a 12V battery bank, and another MPPT 100/20 smartsolar unit. The PV input is a parallell pair of 280W panels with a VOC of 38V, which is being read at the input of the PV isolator to the the controller. The unit has worked for over a year with no issue in the same configuration, however 3 panels were in parallel. I removed one to use as an input to another unit recently. Each panel is fused with a 15A fuse, all of which are intact.

I had recently updated firmware on both my units, and the charger worked for about two or three days after.

Two nights ago there was a low voltage situation in which my battery bank discharged down to the low voltage cutoff of my inverter. In order to allow for the inverter to run a bit longer I switched off all dc circuits, including both chargers. This was about 2 a.m. and ambient night time temperature here is about 30C at night.

The at about 5 30 a.m. or so I switched all dc loads back in, again including both chargers. The MPPT 100/50 showed it produced up to a maximum of maybe 35W up to about 8 a.m. and then stopped producing. The blue light just blinks slowly on the charger, and It hasn't produced at all since. The 20A unit hasn't had any issues.

In the victron connect app it shows that the charger state is off, and reading a voltage of only 13.1V on input. I confirm this with a DMM measuring at the input port of the charger. If the isolator is on and charger is off (isolated from battery) the voltage at the terminals is at the expected level close to VOC.

When the charger is on, it drops to 13.1V and using a DC clamp meter the current goes all the way up to 15A. The battery voltage can be seen to be rising when this happens (I have a BMV monitor as well). If PV is removed from the charger then the voltage of the battery again falls.

I've bypassed the PV isolator in order to see if it may have been that, as well as checked continuity for shorts and changed fuses (even though they weren't blown). I've also tried turning the charger on and off in the app as well as power cycling as per victron recommended procedure. Nothing makes any difference. Assuming my unit is probably toast. The body also seems unusually hot to the touch when PV is connected. Any help/suggestions?





MPPT SmartSolar
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Alexandra avatar image Alexandra ♦ commented ·

Post title should probably read, mppt doesn't work after a system change and firmware update. Or after a low battery disconnect.

@Kahlistrophic

If the mppt doesn't power up from the battery directly (no pv or other source), then it is not working.

What is the voc of the pv coming i to the MPPT - note this only matters if the mppt powers up from the battery.

There is a pre rma test procedure.

https://www.victronenergy.com/media/pg/Pre-RMA_Bench_Test_Instructions/en/pre-rma-test-form---mppt-solar-charger.html#UUID-a02c41de-0c89-5d84-c701-4f28b6ae665b

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kahlistrophic avatar image kahlistrophic Alexandra ♦ commented ·
True, I apologize if the firmware update in title may have been a bit misleading, it's just at the point I count figure out what else if anything maybe the cause of the problem.


The MPPt does power up when connected to battery, and VOC when the array is not connected to the MPPT is 38V or so, but once connected it drops to 13.1V, and currently flow in the array circuit goes up to about 15A.

Thank you for the pre RMA link, I have actually tried a few things on that list. Particularly, checking continuity between PV+ and PV-, as well as PV+ and Batt +. In both cases there is no continuity. I have yet to do a forward voltage drop measurement. I will probably also try putting the two panels on series rather than parallel to see what happens, since even with full current draw on the series string the open circuit voltage should be about 5 volts higher than the battery voltage.

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Mike Dorsett avatar image
Mike Dorsett answered ·

if you have 13.8V on the pv input, with a current of 15A going in, this is also going to charge the battery as you see the battery voltage rising.

It looks like one of the switching FET's in the MPPT has blown short, so the PV + input is effectively connected internally to the Battery + output.

This sounds like a repair or replace for this unit...

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