question

sco avatar image
sco asked

Victron MPPT 100/20 fuse keeps blowing

Hi,

I got the MPPT SmartSolar 100/20 controller a few weeks ago and have so far tested it with solar panels and lead-acid batteries, both in 12V and 24V configurations, and everything's worked fine.

Now however I just got a LiFePO4 battery, 8 cells connected in series for 24V but when trying to connect the battery to the controller (no panels or anything else connected) I get a strong spark and then the controller's (25A) fuse blows. Batteries seem to work as they should, showing voltage of 26.16V. I haven't tried connecting any loads yet.

What could be the issue here? And what should I do to troubleshoot?

MPPT Controllersfuses
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3 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Check the polarity of the battery connections with a multimeter before connecting them to the MPPT.

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sco avatar image
sco answered ·

Obviously I have checked that, it's quite hard to do wrong...

Edit: Apparently it is. Apparently when I initially checked the cell's balance I never registered that the black cell terminals are positive and silver negative. I just assumed that black was negative. Everything is working as it should now!

Luckily the Victron seems well designed so I only got a sooted terminal and a couple of blown fuses.

1 comment
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rickp avatar image
rickp answered ·

I am always reminded to check everything, except the things I’m sure of. Those I check twice! I can’t count the times I’ve had to laugh at myself for missing something really obvious. I’m glad you found the issue!

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