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swiftrv avatar image
swiftrv asked

MPPT 75/15 adding extra Solar panel

Current Setup is as follows.

two 60 watt panels in parallel. So 12 volt system on a Swift Explorer caravan.

mppt 75/15, Two lithium 120 amp hour batteries in parallel.

We find in winter the current system struggles to totally recharge our batteries. Outside of winter it is not an issue.

Question, can I add a 100 watt solar panel.

MPPT Controllers
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1 Answer
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secessus answered ·

two 60 watt panels in parallel...Question, can I add a 100 watt solar panel.

The 15A controller could accept 220w of panels; it would be slightly over the 30% overpaneling described in Victron's whitepaper on the subject.

But MPPT controllers don't particularly like mismatched panels on the same controller. Adding another 60w might actually work about the same, hard to guess without knowing panel specs.


We find in winter the current system struggles to totally recharge our batteries.

Some other approaches to consider:

  • adding in alternator charging. Orion-TR or whatever
  • adding a tilt mount for the existing panels for use in winter, if the problem is low sun rather than cloudy conditions
  • removing the existing 2x 60w and installing a used ~200w higher-voltage panel. In my area the used 200w would cost the same as new 60w and less than a new 100w.


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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.