Switch for 2 Solar Arrays into Single Controller

[Bear in NM]

Another one of my oddball questions for which I have not seen previous discussion.

In my van, I have two 135 watt glass panels on top, and I have a pair of Goal Zero 17's that I keep on my dashboard for driveway trickling to to a Sunsave Duo to top off my main and aux batteries. Currently I manually switch (plug and unplug) between the two depending on what I am doing. Decided now that I have everything working well, it is time to pierce my roof and finalize the installation.

As such, I am trying to set up a manual switch inside the van. I have a Blue Sea Mini Rotary switch coming. Have looked at DPDT switches, but their amperage rating and general "robustness" left me uninterested. Hence the Blue Sea.

The Blue Sea is the battery selector switch with only terminals for one side (generally positive). 2 lines in, switch to off, 1, 2 or combined, one line out. Currently my 2 individual solar feeds terminate at the negative buss bar on my Blue Sea fuse panel, and each positive is fused, back feeding my Fuse panel. My Duo controller is fused at the fuse panel. I have gotten info here that the back feeding of the solar is an acceptable method.

It seems to me that using a 2 battery type switch here should work, but I wanted to run it by the hive here.

The second question/thought here is the switch position to combine. My roof panels are wired parallel, so combining the third with the switch would combine in parallel. I also have a Goal Zero foldable 100 watt glass panel that I keep in the van while camping, so I could combine with the switch (plug the 100 GZ into the plug where the dash panels normally connect). I do understand the possible issues with combining different spec panels as far as degrading the overall performance, but I can easily test that, assuming the original question of the wiring is in and of itself safe.

Thanks,

Craig

 

[Rando]

I am not really understanding what you want to do here, or why.

Why do you want to switch between the panels as opposed to leaving them all hooked up all the time? And what is the point of the 17W panels when you have 270 on the roof?

 

[Bear in NM]

Rando,

The benefit of having a second solar input would be to 1) just use the smaller panels to trickle charge when the van is sitting in my driveway for extended times. With the panels behind the windshield, I can quickly remove snow/leaves/bird doo from the windshield exposing them. This is opposed to breaking out a ladder to remove snow etc from top panels. This is more of a off season storage situation. Sometimes I will set the small panels on the outside of the windshield, just depends. The van is a Quigley with lift, the upper panels are too high to easily inspect for debris.

2) I should be able to hook up my portable 100w panel in the event I am camping in an less than ideal sun/shade situation. I would like to have the option of either, or maybe both.

Craig

 

[Rando]

I still don't understand why you would need to switch between them? Assuming the voltages are similar, just put them all in parallel. The charge controller will take care of trickle charging. With 270W on the roof, I also find it hard to believe the 17W panel would ever be necessary. You only need a few Ah a week to maintain the batteries, so it would be a LOT of poop/leaves/snow to need any extra. My camper and truck sits happy all winter with 160W of solar on the roof, and no maintenance to the panels.

Just trying to save you some work/money here.

 

[Bear in NM]

Rando,

I already have things set up for two lines, and right now I just switch plugs. If I decide to use my 100 foldable, I would be doing so when the Van is big time shaded. Trying to plug that in parallel with my glass would be harder than just plugging it in and using the switch. My thinking is that I can test to see if a completely shaded top glass array will pull down the performance of the foldable.

I also like the idea of being able to shut either/both arrays down from sending any volts/amps to my controller. I get that it is not the most cost effective way of doing things, but I am lot OCD about redundancy and back-up plans.

I guess after thinking about my question more, and how things are currently wired, my concern was combining the ground side of the two arrays together, as the switch is just a big honking two pole for the positive side. I am already grounding both panel lines into a single negative bus on my fuse panel, so in essence I have already being doing it.

So I am OCD always, and slow often.....

Craig

 

[Bear in NM]

Verkstad,

Thank you. That makes sense. My aux batteries and aux fuse panel are completely isolated from the van chassis and start batteries.

So with my positive side rotary switch I have a: 1 in, 2 in, a single out. Switch positions: 1, 2, combined or off. If I run the positive from each array into 1 and 2 respectively, with the out to the controller solar positive input, that covers the positive side.

On the negative side I would combine the negatives from each panel into a single wire into the solar controller panel negative input side. This would leave the negatives of the panels permanently combined, not connected to the battery ground.

Switch position 1 or 2 would then connect the selected panel positive to my controller, completing the circuit. In theory, switch position 1 and 2 (combined) would then connect the 2 arrays in parallel (my 2 roof panels are in parallel already). Off would shut everything down.

Does that make sense?

Thanks,

Craig