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pirlbeck's avatar
pirlbeck
Explorer
Apr 15, 2018

Solar experts....Matching solar panels help needed.

About a year ago I picked up 3 unused Kyocera KC50 50Watt panels for almost nothing and would like to put them on my 2009 Lance 845. While open roof space is somewhat limited on this roof, I think I would be able to find room for at least another 50 watt panel and I need help picking a panel that would work well with the 3 I have. I have looked at buying one or 2 larger panels instead of using the 3 I already have and most on these are too large to fit with the available roof space.

Here are the specs from the tag on my existing panels.

Pmax @25C 50W @45C 35.8W
Vpmax @25C 16.7V @45C 14.7V
Ipmax @25C 3A @45C 2.44A
Voc @25C 21.5V -----
Isc @25C 3.1A -----

Max Sys V 600
Series fuse 6A

Dimensions 25-1/8"X 25-5/8" Dimensions are not critical as I will be mounting the 3 panels I already have in one row and the 4th panel will be mounted alone.

Here are couple of panels I am looking at.

https://www.amazon.com/dp/B01CRA5WNU/?coliid=I3NDL237AHNBVG&colid=11UZ2A09YMR7C&psc=0&ref_=lv_ov_lig_dp_it

Maximum Power Pmax 50 W* (0%, +3%)
Cell type Poly silicon
Voltage at Maximum Power Point Vmpp 17.5 V
Current at Maximum Power Point Impp 2.86 A
Open Circuit Voltage Voc 22.0 V
Short Circuit Current Isc
3.17 A
Module Efficiency (%) 12.5%
Temperature Coefficient of Voc -0.37% /oC
Temperature Coefficient of Isc +0.035% /oC
Temperature Coefficient of Pmax -0.50% /oC

https://www.amazon.com/dp/B0159PHIXW/?coliid=I1VEFUGQTEKM21&colid=11UZ2A09YMR7C&psc=0&ref_=lv_ov_lig_dp_it

Maximum power (Pmax): 50W
Voltage at Pmax (Vmp):17.2V
Current at Pmax (Imp): 2.91A
Open-circuit voltage (Voc)?21.6V
Short-circuit current (Isc)? 3.23A

This last one looks pretty close to me, or am I missing something?

With 3 panels, I had planned to wire all 3 in series but if I add a 4th panel I may do 2 panels in series and then parallel the 2 series sets together.....provided my factory Lance 12ga wiring is heavy enough. I really would like to avoid pulling or routing new, larger wiring from the roof down to the solar charge controller. I installed a Trimetric 2030 and wired in a second battery that sits in the bed of the truck and pulling new wires/cables is not a lot of fun in a smaller truck camper like this 845. I can use larger wire/cable from the controller to the batteries, so that is not an issue. If the 12ga wiring is not heavy enough I would probably wire all 4 in series.

For a charge controller I am planning on a Victron SmartSolar MPPT bluetooth controller.

Also, what size fuse(s) would I need for either way of wiring?

Sorry about the length of this.

Thanks!

55 Replies

  • IMO you are wasting money and effort going MPPT with the three 50s.

    As previously stated in your other thread on this, IMO you should just get the Bogart solar controller that goes with your Trimetric 2030 and put those three 50s in parallel. Amps to the battery will be nearly the same. ( I have three 100s and have tried both ways and it makes no diff)

    You might find your 150w is enough for what you do. Right now you are just speculating you will want /need that fourth 50. If you did turn out to want/need it, you can do better by ditching one of your free 50s and getting say, one 160w panel if it will fit, to make a 260. With PWM, you can mix panel sizes easily, no worries about matching so closely so to not confuse the tracker in an MPPT.

    So your best move is -- install the three 50s with the Bogart PWM and try it out camping. Then you will know what if anything would be a good upgrade. Since 150 is a lot for a truck camper usage of 12v, it is quite possible that you won`t need any upgrade.
  • KD4UPL wrote:
    If you put all 4 panels in parallel you will need 4 "string" fuses; one in series with each panel. If you do 2 strings of 2 panels each then you won't need any string fuses.


    Please explain this......why would I not need 2 string fuses if I do the second option?
    Thanks!
  • The second panel is a better match.
    Ignore the specs on yours for 45C, the standard rating is 25C and that's what modern panels will use. If you are connecting in series the Imp is the most important. If you are connecting in parallel the Vmp is the most important. But for you they are both closer on the second panel you have listed. It will work well enough; not technically a perfect match but who cares.
    If you put all 4 panels in parallel you will need 4 "string" fuses; one in series with each panel. If you do 2 strings of 2 panels each then you won't need any string fuses.
    I would install a breaker on the positive PV wire going into the charge controller to act as a disconnect switch for servicing.

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