100 Watt Panels: Higher Voltage or Higher Amperage?

AuricTech
AuricTech Solar Expert Posts: 140 ✭✭
Situation:

Renogy has two rigid* 100W panels. The monocrystalline panel has a Vmp of 18.9 volts and an Imp of 5.29 amps. The polycrystalline panel has a Vmp of 17.8 volts and an Imp of 5.62 amps. The monocrystalline panel currently costs $16 more than the polycrystalline panel ($149.99 versus $133.99).

Question:

Assuming a PV system mounted on the roof of an RV (with short wire runs of appropriate gauge, some air space between the panels and the roof, and sufficient roof space that the dimensions of the two panels are irrelevant), is there any reason to prefer the higher-voltage panel over the higher-amperage panel?

*Renogy also has a bendable monocrystalline 100W panel, currently priced at $199.99, with a Vmp of 17.7 volts and an Imp of 5.7 amps. Given the lack of a 25-year 80% output warranty (which the other two panels have), I am not considering these for a rooftop RV system.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: 100 Watt Panels: Higher Voltage or Higher Amperage?

    If you are using an MPPT charge controller--Either panel is just fine--Your choice.

    If you are using a PWM charge controller, the "lower voltage" one will give you slightly more charging current (per the specifications).

    If you are in a very hot climate with a cool (not hot) battery bank, you may get a bit better charging (higher Vmp-array) from the higher Vmp voltage panel.

    To address hot panel/cold battery "issue"--Put either two panels in series with an MPPT charge controller--Low Vmp-hot-array voltage "issue" goes way on a 12 volt battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • AuricTech
    AuricTech Solar Expert Posts: 140 ✭✭
    Re: 100 Watt Panels: Higher Voltage or Higher Amperage?

    Thanks for the feedback, Bill. That's pretty much what I figured (which is why I made sure to specify assumptions that would indicate that I took voltage drop due to wiring and heat into account).