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giovanni-perrotta avatar image
giovanni-perrotta asked

MPPT 75/15 wrong battery voltage

Hi all,


During this lockdown I finally installed the solar panel on my father's campervan, a 100w panel paired with the MPPT 75/15.

I'm not new to Victron products since I use them regularly at work on boats, but this time I can't figure out what the problem is.

I've already read the posts regarding similar problems around here but none of them seems to have a solution.

The VE Direct software reads a 13.65V at the battery, and while it is true at the MPPT battery terminals, when I go to the actual battery terminals, the multimeter shows 12.7V, as does the integrated multimeter in my campervan control panel. Plus, I have a charge distributor to the engine battery which starts as soon as the service battery passes 13.5V, and it didn't go off.

A few context:

- installed 2 weeks ago, and it worked perfectly, or at least, we thought, until we connected the Bluetooth dongle. It did never go over 12.7V at the battery, and it was floating, so I guessed it was ok;

-the fuse is ok, it's not blown

-the settings for the batteries are the stock ones.

-the panel itself is working great

-once I connect the RV to the house power, the battery charges over 12.7V and the distributor sets off and starts charging the other battery as well.

Any idea about how to solve the problem? Or maybe, a cause?

MPPT Controllers
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3 Answers
JohnC avatar image
JohnC answered ·

Hi @Giovanni Perrotta

Wires flowing little or no current don't show different V at either end, unless there's an interruption somewhere. This could be something hidden like a bad terminal crimp or other things. But if you've a fuse in there, that'd be a good place to start. It may not be blown, but it may be faulty.

A handheld multimeter should soon find it, but in the absence of one, maybe a separate wire touched over relevant areas while watching the mppt V reading, might find your issue.

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giovanni-perrotta avatar image
giovanni-perrotta answered ·

Hi @JohnC

I've already tested the the 20A fuse on the MPPT module, now I'm going over the whole electrical line, which was in place since we bought it, probably installed by the previous owner.

The fuse has been tested with a multimeter and there's no problem on it, but I have a strange continuity value from one end of the positive cable and the other, after writing the post I found it out,, so now I'm basically removing a whole bunch of furniture to find out what's going on.

I mean, I could expect a voltage drop over the cable, but not a bump actually...

I'll update as soon as I get to any point, either finding the problem or not and having to start over from scratch!

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JohnC avatar image JohnC ♦ commented ·

Yeh, seems you're onto it. Run a new cable if you think the existing one is damaged within the insulation. The existing one may have been stretched or left flopping about for years, the copper within work-hardened and cracked. Stay safe. Good luck..

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radu avatar image
radu answered ·

Hi,

I see the same behaviour on my site: the app shows 13,81, the battery has 11,7 (measured at the cable ends at the mppt). That's why the battery is not beeing loaded. So what is wrong now?

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