question

camper-craig avatar image
camper-craig asked

High battery reading at mppt

Hi, I'm no longer getting Solar charge to my caravan battery. Swapped my 100/20 to a 100/50 after thinking the smaller one was faulty but this is doing the same. I also thought the larger may charge the lithium battery better.

Checking with multi meter, I have 13.3v at the battery as the bmv shows. At the mppt it shows 20v from panel, no watts and the battery terminals are reading 16v. Is this what it is trying to send to the battery or what it thinks the battery is at. Victron connect isn't showing current on the solar page but is on the bmv page. All was working great for quite a while keeping it topped up but now I'm getting nothing.

MPPT Controllers
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2 Answers
klim8skeptic avatar image
klim8skeptic answered ·

You have a high resistance joint/component between the mppt and battery.

You have a multimeter. Measure the voltage (drop) across every component between the mppt and battery, when the mppt is charging the battery.

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What a surprise. Started following the line and found where the previous owner had put an inline fuse. The female spades on the wire were too big for the fuse holder so they had used cable ties to pull the wires together with the fuse holder in between. This had worked loose and separated on one side. Glad nothing more serious had happened. Replaced with a 60amp midi fuse and charging correctly again. I can see another inline 40amp fuse that is very difficult to get to but hoping it wasn't done in the same way.20210521-131354.jpg

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Please check the gauge wiring that is running between the battery and Mppt. It now needs to handle 60a without burning up.

Congrats on finding the problem.

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randy-putnam avatar image
randy-putnam answered ·

Need a bit more info.. You stated voltages at PV and at battery (LFP? total AH?, charging specs?) What is the amperage going from the panels to the battery, as measured via the MPPT and BMV? Are you using Victron Connect and reading this off your Smart phone or tablet? You may have to change some settings for the MPPT to meet your battery specs. I would also consider disconnecting the PVs before making the switch to the different MPPT. Finally, it almost sounds like your batteries are fully charged, or at least assumed so by the MPPT and BMV. In my case I lined the MPPT and BMV via the network on Victron Connect. That way the BMV controls the charging parameters of the MPPT.

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Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.