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benjiebell avatar image
benjiebell asked

MPPT not working, only lights up with mains hook up

My Victron 100|50 MPPT isn't working even on a bright sunny winter day with no shade. I also have a V Smart Charger and when that was working the other day (I rarely hook up) I noticed the lights on the MPPT were on.


Background and context: I've had an electrical system designed and installed by Off-Grid Campers Ltd with lots of installation issues, to the point he's stopped answering my calls or reading my emails/text messages. So I'm a complete notice trying to fix issues - last week I tracked down two loose wires and corrected a series in the wrong order, so I don't feel confident attributing any expert knowledge to the installer.


When it stops pouring with rain(!) I'm going to step through the installation with a multimeter as per the troubleshooting guide and would like to know what to look for. Is it possible he's connected the MPPT to mains power rather than the battery, or should I be looking elsewhere?

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JohnC answered ·

Hi @Benjiebell

Sorry to hear of your plight. What you need to see on the mppt terminals is Battery V and Panel V. The mppt won't even attempt a start unless Panel Voc is 5V greater than Vbat. Then once it tracks Panel Vmp, that should be >1V more. It's possible that the panels are wired incorrectly and Voc/Vmp are too low. You'll need sun, don't forget that..

Ac mains power has no place anywhere near your (all-dc) mppt.

This is a start point. Where this takes you towards other upstream issues we'd just be guessing.


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benjiebell avatar image benjiebell commented ·
Thank you John. I may not have been very clear so I'll try to summarise it better:


I first realised there was an issue on a really bright, full sun day in our winter: there should have been PLENTY of voltage and definitely no shade or temperature issues.


The MPPT is dead or dormant and only lights up when I'm hooked up to mains power.


I understand this shouldn't be the case so am looking for guidance on how to diagnose where the issue is?

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