Need Help: SmartSolar MPPT 100/30 Not Charging Properly – New Setup in RV Rebuild

DIY
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1

Hi everyone,

I’m currently rebuilding an old RV and recently installed a Victron Energy system, but I’m running into some issues I hope you can help with.

Here’s my setup:

  • Victron SmartSolar MPPT 100/30
  • 2x 200W solar panels in parallel
  • 2x 140Ah AGM batteries in series (so 12v
  • Victron battery monitor bmv-700

The batteries are brand new and the system is only a couple of weeks old. However, I’m seeing strange behavior:

  • The bmv-700 shows the battery is charging very slowly — about 1–1.5% per day, currently at 74%.
  • In the VictronConnect app, the MPPT often shows 0W input, even on sunny days.
  • Occasionally it charges between 40–160W, but this is inconsistent. 1 every 15 days or so
  • The Total Yield (Wh) in the MPPT app still shows 0, even though I’ve seen some watts going through before.

I’ve checked:

  • Fuses — no blown fuses between the MPPT and batteries as far as I can see
  • MPPT fuse — appears fine (I assume I’d see an error otherwise?).
  • Connections — all look tight and secure.
  • Settings — using preset 2 in the MPPT.

I went back to the store I bought it from, but they don’t offer support. Victron said they don’t support end users directly. And the local RV shop wants to take the whole system out and redo it for ~€3k, which I’d really like to avoid — everything is brand new and I feel like it might just be a configuration or wiring issue.

I’d really appreciate any help or ideas on what to check. Would uploading some screenshots of my MPPT and battery monitor settings help? I’m fairly new to Victron, so any guidance would be great.

Thanks so much in advance :folded_hands:

p.s. attached screenshot of the app and a photo of the battery monitor

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2

If the two images are taken at the same time then the answer is there and is the cause of 90% of the issues we see with DIY installs, a poor connection between the output of the MPPT and the battery. The MPPT output is at its max voltage, 14.4V but the battery is at 11.4V.

Do you have a multimeter, use that to look for voltage drop. Check every crimp, terminal, fuse, breaker or isolator for the missing 3V.

Are you using cheap ebay/ Amazon no name thermal breakers, these often cause high resistance, ditch them if you are and use fuses and an isolator.

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3

And get those batteries charged pdq because 11.4V is not being kind to AGM batteries.

4

Yes, the images were taken at the same time.

We use a fuse box with screwable fusses and all the fuses are good but I will replace them.
Between the MPPT and the battery we use a 100% OFC coper 25mm2 cable. The only other thing is we have a main switch between the fuse box and the batteries and the fuse box and the solar panels, maybe this main switch is broken since we do not have other elements integrated. So I will get a spare main switch and exchange all fuses and get back to you.