Charge Controller help

johnm1

New Member
Joined
Feb 5, 2021
Messages
14
I've started to plan out a solar set up for a 5th wheel camper (that we haven't purchased yet) and I could use some guidance please.

I want to start with 6 x 210w panels and have an option to add 2 more when we're ready. I want the 2 extra panels to be pretty much "plug-n-play" when it's time.

Hightec Solar 210W 36 Cell 12V Nominal Solar Panel - 6 Busbar:
  • Power: 210 Watt
  • Vmp: 22.42V
  • Voc: 24.9V
  • Imp: 9.37A
  • Isc: 9.85A
I'm planning to wire the original 6 panels (plus the extra 2 in the future) in parallel. I'm planning out a combiner box with MC4 bulkhead connectors that will handle 8-10 panels (just in case). The panels have 12awg wire and I'm going to use 4awg from the combiner box to the solar charge controller ... unless someone convinces me to use something else.

I like Victron Energy equipment. So my question is, should I use ...

(2 x) Victron Energy 50A SmartSolar MPPT 100/50 Charge Controller w/ Bluetooth
  • Battery Voltage: 12V/24V Auto Select
  • Rated Charging Current: 50A
  • Maximum PV Short Circuit Current: 60A
  • Maximum PV Open Circuit Voltage: 100V
  • Nominal PV Power (12V System): 700W
  • Nominal PV Power (24V System): 1400W
  • Terminal Connection Size: 6AWG (13mm²)
-or-

(1 x) Victron Energy SmartSolar MPPT 150/100-Tr Solar Charge - VE.Can
  • Battery Voltage: 12V/24V/48V Auto Select (software tool needed for 36V)
  • Rated Charging Current: 100A
  • Maximum PV Short Circuit Current: 70A
  • Maximum PV Open Circuit Voltage: 150V
  • Nominal PV Power (12V System): 1450W
  • Nominal PV Power (24V System): 2900W
  • Nominal PV Power (36V System): 4350W
  • Nominal PV Power (48V System): 5800W
  • Terminal Connection Size: 2AWG (35mm²)
Thanks for any help!
john
 

MisterSandals

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Joined
Nov 5, 2019
Messages
4,825
Location
Silicon Valley
(2 x) Victron Energy 50A SmartSolar MPPT 100/50 Charge Controller w/ Bluetooth
  • Maximum PV Open Circuit Voltage: 100V
This works really well for 3 of your 24Voc panels in series. You wouldn't even need a combiner box.
I like the idea of 2 distinct systems for redundancy and you'd be able to potentially have arrays in different ends of the RV to reduce the affects of any shading between the 2 arrays.

For your planned expansion, i would consider having pigtails to add another carry-out array to a smaller Victron 75/15 or similar. I don't know about you but i like to park in the shade when its hot out. Being able to carry out a couple panels into the sun and plug them into some pigtails with 25' leads would be easy enough.
 

johnm1

New Member
Joined
Feb 5, 2021
Messages
14
Hmmm .... I just realized that at 210w/12v nominal for the panels, I'm putting too many watts into either charge controller if I wire everything parallel.

Victron 100/50: rated for 700w @ 12v or 1400w @ 24v
- and -
Victron 150/100: rated for 1450W @ 12v or 2900w @ 24v.

Again, I'm starting with 6 x 210w panels = 1260w and (hopefully) going to a total of 8 x 210w panels = 1680w@ 12v nominal.

Looks like my options are ...
Option A:
Run the first set of 6 x 210w panels to the Victron 150/100, which would be 1260w and then "future proof" with a 2nd set of wires for the 2 future panels run to another Victron CC of the required specs.

Option B (this seems like the better option?):
Wire the panels in series "sets" to get under the max watts of the Victron 100/50 and use 2 of them

How do you do the math when panels are in series??? ... this makes my head hurt.
 

MisterSandals

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Messages
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Location
Silicon Valley
How do you do the math when panels are in series?
In series, the volts are added.
In parallel, the amps are added.

So 3 panels in series, 24.9Voc = 74.7Voc and 9.85Isc
You can run an array like this to a 100/50 (twice).
630W / 12.8V = 49A charging

or
2 of these strings connected in parallel, produces 74.7Voc and 19.70Isc

1260W / 12.8V = 98A charging

You cannot run 6 of these panels in series with a 150V SCC as voltage with rise as temp drops below 25C where they are rated.
 

HRTKD

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Apr 24, 2020
Messages
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Location
Somewhere South of Denver
Before you start planning too much and start buying stuff, I would caution you to hold off until you have the RV on site. Maybe those size and number of panels will fit and maybe they won't. RV trailers are notorious for having objects on the roof randomly placed. Until you have a measured, to-scale, drawing of the roof and the panels you don't really know if they'll fit.

Panels that are mounted using Z brackets take up an additional 1.5" on both sides of the panel. A rack system can fit panels in a tighter configuration, but the rack system adds cost (and height) to the project.

Without running the numbers, my preference would be to go 3s2p. No fuse required. No combiner box required.
 

johnm1

New Member
Joined
Feb 5, 2021
Messages
14
Before you start planning too much and start buying stuff, I would caution you to hold off until you have the RV on site. Maybe those size and number of panels will fit and maybe they won't. RV trailers are notorious for having objects on the roof randomly placed. Until you have a measured, to-scale, drawing of the roof and the panels you don't really know if they'll fit.

Panels that are mounted using Z brackets take up an additional 1.5" on both sides of the panel. A rack system can fit panels in a tighter configuration, but the rack system adds cost (and height) to the project.

Without running the numbers, my preference would be to go 3s2p. No fuse required. No combiner box required.
Yes, you are correct. I'm not going to purchase anything until we get the camper. This will be our 2nd camper that I will install solar on and I'm just in the planning stages.
 

carl2591

New Member
Joined
Nov 16, 2019
Messages
32
This works really well for 3 of your 24Voc panels in series. You wouldn't even need a combiner box.
I like the idea of 2 distinct systems for redundancy and you'd be able to potentially have arrays in different ends of the RV to reduce the affects of any shading between the 2 arrays.

For your planned expansion, i would consider having pigtails to add another carry-out array to a smaller Victron 75/15 or similar. I don't know about you but i like to park in the shade when its hot out. Being able to carry out a couple panels into the sun and plug them into some pigtails with 25' leads would be easy enough.
I can the same thing but a 335 W 24V panel on top of camper shell of pickup.. with 40 ft of line to a separate 20 amp MPPT controller.. park in shade and get a heck of a lot of power when needed.. (the mppt can turn the 8 amp into 18 amps no problem) only needed to use the whole length couple of times but nice to have it.
 

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