Forum Discussion

TUCQUALA's avatar
TUCQUALA
Explorer
Oct 07, 2016

Another Solar "??"

Have this mono panel on trailer:

Maximum Power: 150W
Maximum System Voltage: 600V DC (UL)
Optimum Operating Voltage (Vmp): 17.90V
Open-Circuit Voltage (Voc): 22.5V
Optimum Operating Current (Imp): 8.38A
Short-Circuit Current (Isc): 9.05A
Dimensions: 39.5 X 39 X 1.4 In
Weight: 26.5lbs

Using EPsolar Viewstar VS2024BN PWM Solar Battery Charge Controller 20A 12/24V. Looking to add one more of same panel. What would be best: parallel or series?? If serial would be best for battery charging, obviously need to go to a mppt controller. If parallel, would the 20A Viewstar handle a second panel??

Other choice is to add this panel:

Maximum Power: 100W
Optimum Operating Voltage (Vmp): 18.9V
Peak Current (Imp): 5.5A
Open-Circuit Voltage (Voc): 21.08V
Short-Circuit Current (Isc): 6.04A
Connectors: MC4 Connectors
Model:100W Monocrystalline Solar Panel
Cell Type: Monocrystalline
Solar Cell Grade: Grade A
Dimensions: 26.4" X 39.9" X 1.4"
Weight:16.5#

This would fit easily, as would the first, and provide slightly output at less cost. Same questions as above!! Parallel or series?

Thanks in advance!! Will try to answer any necc questions the experts will ask!!
  • TUCQUALA's avatar
    TUCQUALA
    Explorer
    Oct 09, 2016
    Thanks for the replies, kinda what my thoughts were. Parallel, but wasn't sure of the amps to the controller. Panel 1 ordered (!!) to match the one on trailer.

    Really like the Viewstar, also have the MT50 remote readout and it is very versatile!! Easy to keep track of what's happening.

    Tanks agin'!!

    Gerry
  • westend's avatar
    westend
    Explorer
    Oct 08, 2016
    Parallel, for all the good reasons mentioned above and use the same Viewstar controller.
    I think you'd have to be parked in the high desert on Jun 21st at noon with cloud effect and a string of ballpark lights above to ever reach close to 20 amps output from the panels.
  • hedge's avatar
    hedge
    Explorer
    Oct 08, 2016
    ^ same, I have 300w and it fits my small roof (truck camper) well and does the job but then Amazon has a deal on the same 100w panels I have (Renogy) today... I almost bought another one.

    Probably would have but trying to save some room on the roof to install a rack so I can haul some kayaks.
  • BFL13's avatar
    BFL13
    Explorer II
    Oct 08, 2016
    I keep getting too much solar and then I sell some but then I over-do that so I buy some more. I know very well how much is enough and how much is too much, but I can't resist a sale price so I keep ending up with too much. :(
  • grizzzman's avatar
    grizzzman
    Explorer
    Oct 08, 2016
    TUCQUALA wrote:
    Have this mono panel on trailer:

    Maximum Power: 150W
    Maximum System Voltage: 600V DC (UL)
    Optimum Operating Voltage (Vmp): 17.90V
    Open-Circuit Voltage (Voc): 22.5V
    Optimum Operating Current (Imp): 8.38A
    Short-Circuit Current (Isc): 9.05A
    Dimensions: 39.5 X 39 X 1.4 In
    Weight: 26.5lbs

    Using EPsolar Viewstar VS2024BN PWM Solar Battery Charge Controller 20A 12/24V. Looking to add one more of same panel. What would be best: parallel or series?? If serial would be best for battery charging, obviously need to go to a mppt controller. If parallel, would the 20A Viewstar handle a second panel??

    Other choice is to add this panel:

    Maximum Power: 100W
    Optimum Operating Voltage (Vmp): 18.9V
    Peak Current (Imp): 5.5A
    Open-Circuit Voltage (Voc): 21.08V
    Short-Circuit Current (Isc): 6.04A
    Connectors: MC4 Connectors
    Model:100W Monocrystalline Solar Panel
    Cell Type: Monocrystalline
    Solar Cell Grade: Grade A
    Dimensions: 26.4" X 39.9" X 1.4"
    Weight:16.5#

    This would fit easily, as would the first, and provide slightly output at less cost. Same questions as above!! Parallel or series?

    Thanks in advance!! Will try to answer any necc questions the experts will ask!!


    In my opinion it would be a waste of money buying a MPPT for such a small array. You already have the PWM controller. Run another parallel wire run with the 150 Watt panel. (When do you ever hear someone say "I have to much solar!")(My wife is the exception :R) If the controller fails then rethink your choice's.
    Above all have fun!
  • JFNM's avatar
    JFNM
    Explorer
    Oct 07, 2016
    DrewE wrote:
    You mixed up series and parallel here.


    Oops - you are right! Sorry about that! :S
  • DrewE's avatar
    DrewE
    Explorer II
    Oct 07, 2016
    JFNM wrote:

    Edit: Sorry, didn't answer all your questions. You can add a second 150 watt panel. If connected in series, you would see a maximum of 22.5 volts and 16.76 (8.38 amps times two). If connected in parallel, you would see a maximum of 45 volts (22.5 volts times two) and 8.38 amps. According to the specs I see for your controller, both are within it's limits. Also remember, panel "max" specs are under ideal conditions which don't exist in the real world.


    You mixed up series and parallel here.

    Putting power sources in parallel would force them to operate at the same voltage (the single panel voltage in this case) and the currents would sum. Putting them in series would have the same current flowing through both (the single panel currents) but the voltages would sum.
  • BFL13's avatar
    BFL13
    Explorer II
    Oct 07, 2016
    You can get Isc so two would be 18 amps which is under the 20a of the controller, but does not leave much margin. If the panels are flat and not usually aimed directly at a high sun, you could do it. IMO go for it.

    (The risk of going over 20a for a time is the controller will overheat and fry itself at some point. Brief times of cloud edge effect don't matter.)

    Yes if you go series with that controller you will get 9 amps instead of 18 with parallel.

    No point going MPPT for another couple amps (if you even get them) when you already have a good controller. I have used a LandStar-very good controller.
  • red31's avatar
    red31
    Explorer
    Oct 07, 2016
    epsolar does not list a max input wattage just 'rated 20A battery current'.
    They do not suggest what happens if input exceeds 20A, does it shut down or clip?
    2 150 watt panels may exceed 20A in the 'right' conditions.
    I'd risk it and go with parallel 150s and the ViewStar.
  • JFNM's avatar
    JFNM
    Explorer
    Oct 07, 2016
    Howdy TUCQUALA,

    I'm a fan of series unless limited by your controller.

    I'm not familiar with your charge controller so had to look it up. It appears that it will take a maximum input voltage of 48 volts. Based on that, I would go series. However; confirm that the unit you have in hand matches what I found.

    Edit: Sorry, didn't answer all your questions. You can add a second 150 watt panel. If connected in series, you would see a maximum of 22.5 volts and 16.76 (8.38 amps times two). If connected in parallel, you would see a maximum of 45 volts (22.5 volts times two) and 8.38 amps. According to the specs I see for your controller, both are within it's limits. Also remember, panel "max" specs are under ideal conditions which don't exist in the real world.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,190 PostsLatest Activity: Jan 22, 2025