Second Victron SmartSolar MPPT 100/50 Still Throttling at ~295W – What Am I Missing?

DIY
1

Hi all,

I’m trying to track down a persistent performance issue with a Victron SmartSolar MPPT 100/50 in my 2025 Winnebago EKKO 22A (Transit chassis).

This is the second controller I’ve tested — the first one was returned because it appeared to be throttling inexplicably. The replacement is behaving identically.

Here’s my setup and test data:

  • Roof panels alone (3 panels total): ~292W
  • Portable panel alone (200W rated): ~117W
  • Roof + portable together: spikes briefly, then throttles back to ~289–295W
  • All panels output ~20V, no mismatches
  • Polarity confirmed on all wiring
  • Rotary switch set to 7 for LiFePO4
  • Battery: Lithionics, ~76% SoC, 95°F — definitely not full
  • Heatsink temp: 96°F (measured via IR thermometer)
  • Wiring: factory 6 AWG, over 10 ft to battery
  • Victron app shows no faults or warnings
  • A/C running to guarantee active load

Despite ample solar and a partially charged battery, total reported output remains capped at ~295W. I’ve tried various combinations of panels, and the result is always the same — a hard ceiling just under 300W.

What’s most frustrating:

The stock Xantrex PWM controller performed better than this in the same conditions.

Questions:

  • Is this a known issue with this controller?
  • Is there some other setting that needs to be tweaked?
  • Could long wiring alone account for this behavior (despite the controller reporting ~20V from solar)?
  • Is this another defective unit, or is it behaving as designed?

Thanks for any help — I’ve spent days troubleshooting this now and would love to hear if anyone has dealt with something similar or has ideas for further testing.

2

Use VictronConnect app to give us screenshots of your settings and the status page when the charging is limited. Also details of your panels, Voc, Isc, Vmp, Imp, power and number panels and arrangement.

Also, when you are charging measure the voltage at the battery terminal and the mppt terminals with a multimeter or report the battery voltage from the battery app if it is Bluetooth enabled.

3

All panels have the same number of cells?
Same cell type?

4

Thanks for the good questions. Upon additional research, it has come to light that the victron controller does not play well with the lithiopnics battery. Apparently the charge controller needs to communicate on the CAN bus in order for the lithionics to accept the charge.