Panel voltage though MPPT...?

RVoutreachRVoutreach Registered Users Posts: 7
Hello everyone.

I am looking to add 2 solar panels to my travel trailer to keep my 2 Trojan T-105 batteries up. I have limited roof space to install panels so want to get the largest output I can. I had originally looked at the Evergreen ES-A 195 units but cannot fit 2 of those on my roof due to their size. I have 84" x 55" of open space on the roof in which to place 2 panels.

I found the Kyocera KD180GX-LP 180 Watt Solar Panel after doing some searching and found that 2 of these will fit on my roof. The specs are:

Max Rated Power (Pmax) 180 Watts
Voltage at Max Power (Vmpp) 23.6
Current at Max Power (Impp) 7.63 Amps
Open Circuit Voltage (Voc) 29.5
Short Circuit Current (Isc) 8.35 Amps
Length x Width x Depth (inches) 52.8 x 39 x 1.4
Weight of Panel (Pounds) 36.7

My questions are these:

1. Is this a good panel choice for my needs? If not, suggestions are appreciated.

2. If I run these through a 30a MPPT charge controller, will they be suitable for charging a pair of T-105s?

3. Is a 30a controller sufficient?

Also, I have no intention of running the A/C or the microwave when not connected to shore power. Just 12v LED lights as needed before bed time, a 12v fan all night, and a 26" LCD TV and a DirecTV satellite box for about 1 hour per day. The fridge will run on propane and the water pump will be turned on only as needed. Will also run a cell phone charger once every 3 days or so.

My apologies if these are dumb questions, please consider the source. :blush:


  • mike95490mike95490 Solar Expert Posts: 8,761 ✭✭✭✭✭
    Re: Panel voltage though MPPT...?

    While 30A is close to the limit, I believe the charge controller is supposed to protect itself, and your panels, when warmed up, will output less than nameplate.
    BUT - you should get the remote battery temperature sensor, because the charge controller will be running warm, and will have incorrect charge setpoints for the actual battery temperature.

    Also, be sure the cold start, open circuit voltage does not violate the charge controllers input limit.

    What is the charge controller you are looking at ? There are some "duds" out there.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

  • RVoutreachRVoutreach Registered Users Posts: 7
    Re: Panel voltage though MPPT...?

    Morningstar is main brand that I am considering. Was told they have a 45a MPPT coming in September but I do not know the price or stats of it yet. Others I have looked into are BlueSky and Xantrex.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Panel voltage though MPPT...?

    as mike said that is close to the limit and the controller would limit output, but for most mobile type applications i would say that it would not be aimed optimally so a slight reduction of insolation will reduce output some. whether it could keep your batteries up depends on whether you were to drain more from the batteries than the pvs could replace, but the percents look good. work out how much you may drain from them and determine if you may need more pv wattage to keep up the batteries. if you think you may need more then opt for the larger capacity mppt controllers over one that's 30a. the extra capacity may come while parked with a remotable pv in addition to those you employ on the trailer.
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