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Old 11-10-2023, 01:47 PM   #1
Join Date: Apr 2019
Posts: 10
Solar Combiner Box & Parallel Solar Wiring

Hello everyone,

My intention is as follows

To install 8. 425watt solar panels onto the roof of my bus.

The voltage of each panel is 41.3v
And the amperage of each panel is 10.31amp

41.3v x10.31amps= 425w

I want to wire the panels in parallel to remedy shading issues (partial shading of one or two panels affecting the whole array)

But when wiring in parallel amperage increases whereas voltage stays the same

So in this case my amperage would be 82.48 amps

Which would require 3 gauge wire rated at 100amps.

My thoughts are to have two separate arrays with four panels on each array…. This would max out at about 44amps or so, which would allow me to use six gauge wire for each array.

I’m wondering the cleanest/ most efficient way to accomplish this?

I would like to fuse the positive of each panel since my amperage is higher than the 10 gauge wire that the panels come with… but I don’t necessarily like the idea of having inline mc4 fuses on the roof of the bus…
Is there some kind of combiner box that is designed for this application?

If I decided to land both arrays on the same charge controller
What would be the cleanest way to parallel those two strings together? (Although I do doubt that Victron actually makes a charge controller than could handle both strings, so I’ll likely need two charge controllers anyway.

Ok thanks y’all

Happy to receive any insight that you feel inspired to offer

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Old 11-10-2023, 01:48 PM   #2
Join Date: Apr 2019
Posts: 10
Also, it’s a 24v system fyi.
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Old 11-10-2023, 04:54 PM   #3
Join Date: Apr 2019
Posts: 10
Nvm guys! I got it sorted

Using this midnite solar unit
That is designed for exactly what I’m trying to do
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Old 11-10-2023, 06:26 PM   #4
Bus Crazy
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Join Date: Nov 2014
Location: NM USA KD6WJG
Posts: 1,313
Year: 1991
Coachwork: Bluebird
Chassis: All American RE 40 FEET
Engine: Cummins 8.3
That is a lot of money for some thing you could diy.
Why can't I get Ivermectin for my horses?
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Old 11-22-2023, 05:35 PM   #5
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Join Date: Sep 2019
Location: Bly Oregon
Posts: 527
Year: 1986
Coachwork: Crown
Chassis: Supercoach
Engine: Cummins 350 big cam
Rated Cap: 86 passengers?
I made my own terminal block using machinable plastic, flattened copper tubing and 1/4-20 nuts bolts and washers. Each panel is in parallel with 10 gauge wires coming through the extruded channel that Crowns use to mount speakers and lights. The current flow from each panel is way below the limits for 10 gauge wire, so no heating issues. With the terminal block I fabricated I connected all five panels negative side to one copper buss. For the positive side I isolated two panels that connect through a switch to a second charge controller for charging the Crown's starting batteries OR to the first charge controller to charge the RV batteries. This way, with the flip of a switch I can separately charge the starting batteries with two panels OR put all of the power into the RV batteries. When I am on the road it makes sense to put all 1000 watts of solar power into the RV batteries, but when storing the Crown I keep all batteries charged.
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Old 11-23-2023, 07:46 AM   #6
Bus Nut
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Join Date: Jul 2019
Location: Freedom Field, New Mexico
Posts: 457
Year: 1998
Coachwork: International
Chassis: Amtrans
Engine: 444E
Rated Cap: 84 pas
DIY and save big bucks

Originally Posted by Mobobaddon View Post
Nvm guys! I got it sorted

Using this midnite solar unit
That is designed for exactly what I’m trying to do
We did a similar setup on the bus we are full timing in. 12 327W solar panels. Three 4 panel arrays. Each four panel array has a combiner box made with off the shelf ground strap bars from the big box store, contained in weather proof electrical project box.

6 gauge wire to 3 solar controllers. The three controllers feed our 24v battery bank and 6kw inverter. (We like comfort).
Ran that system from early 2019 till August this year.

Replaced the three controllers with an eg4 off grid hybrid inverter.
Put the panels in a 4P3S configuration and didn't have to go up on the roof to do it.

All the inputs combine to two an feed the eg4.
Upgraded our 24v battery bank to a 48v batter built out of 32 280ah grade A EVE cells.

Loving the not caring about cloudy days.

Moving to the new build soon. We are adding four slide out solar panels for a total of 16 400w panels going 4P4S

Using the same type of DIY combiner boxes. Bout $25 bux a box.
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