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Evan Kruckow avatar image
Evan Kruckow asked

MPPT not bulk charging

Hi All,

I am trying to troubleshoot the behavior of the Victron 75/15 MPPT I have. Basically this is part of a portable solar setup for camping and I purchased the Victron controller to replace the previous cheap controller that gave up, the wiring for the victron was just copied across from the old controller.

It is a basic fixed panel set up with 160W (from 2 x 80W) panels with the controller and direct connection to the battery, is not complicated. When the panels are set out and battery connected the charge controller has the green light blinking with the yellow light slowly blinking initially, but after less than a minute it goes to constant yellow which is float. At no time does the controller go to bulk charge and this is despite the battery requiring charge. I have tried on several batteries at volts well below full and get the same result. I have checked the panel output and they appear to be operating correctly with a Voc of 20.4 on the multimeter and Amps of around 8. Attached are a few photos of the results any ideas welcomed on how to fix this and get the controller charging, the multi meter is showing the voltage of the battery I have it connected to.

Thanks, Evan20230205-145701.jpg20230205-145707.jpg20230205-145916.jpg

MPPT Controllers
20230205-145701.jpg (1.8 MiB)
20230205-145707.jpg (2.1 MiB)
20230205-145916.jpg (3.2 MiB)
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kevgermany avatar image kevgermany ♦♦ commented ·
Your last picture shows a voltage of 9.69. Where was this measured?

Have you measured the current to the battery?

What size/guage wires are you using?


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Evan Kruckow avatar image
Evan Kruckow answered ·

Thanks Kev, this voltage was at the battery while connected. I have also tried with a different battery not discharged so much so sitting at 12.3V but same result. The cable is relatively light, I'd say 20amp, so somewhere around 9AWG. So not sure what the issue is.

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klim8skeptic avatar image klim8skeptic ♦ commented ·
The controller should be close to the battery, not glued to the solar panel.

Mppt is not waterproof, so undercover plz.

Panel Voc and Vmp are low, below recommended voltages. Wiring the 2 panels in series will help with that.

What current is going into the battery? A bit of time might help to bring the voltage up.

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Evan Kruckow answered ·

I can move the controller and yep understand it is not waterproof, this is how it was setup previous but not ideal. I did have this setup when camping to battery that was only lightly discharged, so 12.3V or so and had the same result with the controller staying in bulk charge. I will need to check current to battery but basically this was minimal as no lift in battery charge

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Evan Kruckow avatar image
Evan Kruckow answered ·

Just checked and when the controller is connected I am only getting 1.79amps at the battery, this is when the controller is fluctuating between float and absorption

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klim8skeptic avatar image klim8skeptic ♦ commented ·
Best to check what the panel voltage is going into the mppt, when that ^ is occurring.
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