Should I upgrade from a PWM to an MPPT with only 170 watts of Panels?

Bass-O-MaticBass-O-Matic Registered Users Posts: 41 ✭✭
edited October 2020 in Solar Beginners Corner #1

Hope all are well. I have 

2 x 85 watt 12v cheap-o poly panels @ 5 amps each for a total of 170 watts and 10 amps.
Mounted flat. With the glue mounts so they have some breathing room under them.
16 feet from panels to PWM 30 watt charge controller. 6 gauge copper welding cable.
2 x 6volt Costco Gold cart batts.

That's all the room I have on my wee RV. There is a PWM controller on them which works fine. Out of pure boredom -- I was wondering if upgrading to an MPPT would squeeze out more charging?

Well, I did notice on our last trip that the panels mostly kept up but we had to turn off the mini fridge. I was right at 12.1 volts for the trip. We were under some trees.

I hear you have to match your MPPT well... so 20 amp? Which one? I'm not too concerned about the cost. Reliability would matter. I hear MPPTs can be more dodgy? Or is that not true anymore?



  • 706jim706jim Solar Expert Posts: 397 ✭✭✭✭
    I don't think it would be worth the bother.
    Island cottage solar system with 2400 watts of panels, 1kw facing southeast 1kw facing southwest 400watt ancient Arco's facing south.Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 27th year.
  • andtimeandtime Registered Users Posts: 8 ✭✭
    If your panels are truly 12v, I think 706 is right--maybe not worth spending money needed for a decent mppt. Mine are 18v, so my pwm was wasting power--and living in N MN, I have less sunlight so wanted to maximize and use the voltage that was being wasted. When my pwm fried, it seemed best to go mppt.
  • InCogKneeToeInCogKneeToe Registered Users Posts: 67 ✭✭

    I used a Sunforce 30A CC at m Cabin, (until I was gifted a Trace C40) both PWM. The Sunforce worked great, gave an "Volt" readout as well as an "Amp" Harvest readout. I was running 4, 100w panels. I ran 2 12awg strings, I can't imagine 6AWG Cable for 185 watts.

    Running any "Fridge" is tricky with such a Small System. I run a small 5cu/ft Bar Fridge, for a few weeks while my Wife is on Vacation. I top off my 650AH bank every night with a Gen Set and 30A Bench Charger, while watching a movie. Some mornings, I have to fire up the Gen Set to climb above 12.3v showing.

  • spacebassspacebass Registered Users Posts: 79 ✭✭
    Definitley upgrade to Epever has temperature facility have to buy plug in separately.
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