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Old 11-29-2020, 07:51 AM   #1
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Couple of Solar questions

AZ wind and sun has some pretty prices on there 360W panels for 250 bucks so I picked up two REC Solar REC360AA panels. Would the ROVER LI 40 AMP MPPT be a good choice for those panels? The panels say 44V and short of 10amps, but 44v at 360 watts is 8 amps. The rover is good for 100V at 50A input. I will add one more pannel in the future.

Also how much solar is needed to recharge a given battery bank? I have right now 12V 400ah (280 useable at 70% DOD on AGM). I also want to add a third 200AH battery. So I kind of assume one pannel per battery is a good rule? As with the 360W pannel I might see 200W output?

Also has anyone had good luck just self tapping or pop rivet the brackets to the roof? Where I plan to mount I don't think but two of the brackets will catch a rib
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Old 11-30-2020, 12:14 AM   #2
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I just used metal roofing screws to attach my brackets to the roof sheet metal. Thereís no way to hit the ribs (hat channel) unless you use a solar rack and bolt those to the ribs then bolt the panels to the rack. If you plan on adding more solar panels later it might be worth installing a rack.
You can only use two of those REC panels in a series string to that controller. Three panels would take you over the 100 volt limit.
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Old 11-30-2020, 04:35 AM   #3
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Quote:
Originally Posted by bigskypc50 View Post
AZ wind and sun has some pretty prices on there 360W panels for 250 bucks so I picked up two REC Solar REC360AA panels. Would the ROVER LI 40 AMP MPPT be a good choice for those panels? The panels say 44V and short of 10amps, but 44v at 360 watts is 8 amps. The rover is good for 100V at 50A input. I will add one more panel in the future.

The way you figure out what size controller to get is, find your panels datasheet (or the sticker on the back):


  1. Multiply VOC x number of panels in series, adjust for low temps (easy way is to multiply by 1.2 or 1.25). This tells you the minimum input voltage the controller needs to be rated for.
  2. Multiply ISC x number of panels in parallel, this tells you the minimum input current the controller needs to be rated for.
  3. Take the power (Watts) multiply by total number of panels, divide by battery bank voltage, this is the minimum output current your controller needs to support (this is a soft limit usually) you can overpanel a bit with most controllers.
Using your panels as an example and assuming you will wire in parallel:
  1. 44.1V x 1 panel x 1.25 = 55V
  2. 10.23 x 3 panels = 31A
  3. (360 x 3 panels) / 12V = 90A
If you were to go with a 24v battery bank you could cut that last number in half


Assuming you stick with 12v,


You'll want a controller that is roughly 80-100A
Input specs won't be the bottleneck here, you just need >55V input voltage and >31A input current.


Expect quality options to be in the ballpark of 500-800 at that size, value options maybe 400-500 possibly slightly cheaper


Victron Smartsolar 150 | 85
Outback Flexmax 80


Epever is a brand to consider for a budget option.
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Old 11-30-2020, 10:11 PM   #4
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Yes never heard of Rover.

Victron SmartSolar, one sized per panel (or v/v) is my reco.
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Old 12-01-2020, 06:57 AM   #5
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Thanks DZL, however I reject your answer LOL, I was not planing on having to spend that much on a controller. I have herd a lot about those Victron so likely will go with that and the midnight classic is that a still a good name?
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Old 12-01-2020, 01:43 PM   #6
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Yes Outback, Midnight, Morningstar, Blue Sky all excellent.

But pricey, only Victron give great value, and that is because the cost per 100W is just as low on their small units like 75/15 so you can optimize MPPT output and minimize partial shading reductions, by 1:1 pairing with high-voltage panels

matching each panel to an appropriately sized SC
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Old 12-01-2020, 03:01 PM   #7
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Quote:
Originally Posted by bigskypc50 View Post
AZ wind and sun has some pretty prices on there 360W panels for 250 bucks so I picked up two REC Solar REC360AA panels. Would the ROVER LI 40 AMP MPPT be a good choice for those panels? The panels say 44V and short of 10amps, but 44v at 360 watts is 8 amps. The rover is good for 100V at 50A input. I will add one more pannel in the future.

Also how much solar is needed to recharge a given battery bank? I have right now 12V 400ah (280 useable at 70% DOD on AGM). I also want to add a third 200AH battery. So I kind of assume one pannel per battery is a good rule? As with the 360W pannel I might see 200W output?

Also has anyone had good luck just self tapping or pop rivet the brackets to the roof? Where I plan to mount I don't think but two of the brackets will catch a rib
I am using Rivnuts to fasten my solar panels to the roof of my Crown. They are installed much like a large pop rivet with a similar tool. They give you the ability to remove a panel if needed. They can be made out of aluminum, steel or stainless steel. You can get them at Fastenal (special order), or eBay. I am using stainless steel for the solar panels. Crown roof panels are about .060" thick and well within the thickness they work with. I am also using insulation between the panels and the roof to prevent heat transfer between roof and panel.
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Old 12-05-2020, 05:01 PM   #8
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I have rover controllers and they're pretty good but basic from my limited perspective. Avoid the pg versions unless your panels are positive ground, and use the LI rovers, which are negative ground and still relatively inexpensive. I'll buy victron in the future to integrate into my inverter, etc. but the rovers haven't let me down.

One of the things that I have found when I switched to 24v from 12v was that controllers were a lot cheaper, and I could run double the panels per controller, so I have 2 305w panels into each rover 30a and it works great. They have a max wattage specification so you can look that up and see what they have as an overall limit. I think its 800W for a 30a controller at 24v but I am not certain.

Last point is that the controllers are cheap enough and redundancy is important enough that I decided to go with two controllers instead of one. they hook up to everything just the same but if you have shade on one panel or something goes wrong you have a fully functional half system still going.

last last bit is that panels to battery capacity changes a lot with location. NM, where I am, panels are rated at their actual rating, where expected capacity in NY where I live prior was derated something like 75% because of latitude and clouds. When you factor in the lack of panel tilt on most skoolies you should de-rate more, but really the best bet is more and more and more panels no matter what, as the chargers won't overcharge batteries and the clouds and winter will ruin your life if you let it.
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Old 12-12-2020, 08:28 AM   #9
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Thanks guys so much for your feedback! Had no ideal you could use two controllers on the same battery bank.

So someone correct me if I am wrong, but my plan now is to use two of the 360 panels on a ROVER LI 40 AMP MPPT then going forward, add two more pannels on a 2nd controller. Putting the two panels in parallel would give me that 40 odd volts but double my amps. So with slight over pannel I should be inside the limit on that Rover controller, the price is good at $144.00
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Old 12-12-2020, 09:39 AM   #10
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Quick math says 720w @ 12v is 60 amps so if youíre going to run a 12v setup you may want to run 2 30a controllers instead of one 40, or run a 24v setup instead with the 40a controller and youíll be just fine. With panels that are flat on the roof and less than ideal sun in the winter youíll likely get away with your plan but you may run into issues if you have Arizona sun at noon and you could overheat the controller. Iím not sure what happens if you over amp the controller practically... I did it and got a warning light but it didnít fry... that being said I didnít let it stay that way too long. 24v systems are way better than 12v if you can do it, Iím happy I switched.

Quote:
Originally Posted by bigskypc50 View Post
Thanks guys so much for your feedback! Had no ideal you could use two controllers on the same battery bank.

So someone correct me if I am wrong, but my plan now is to use two of the 360 panels on a ROVER LI 40 AMP MPPT then going forward, add two more pannels on a 2nd controller. Putting the two panels in parallel would give me that 40 odd volts but double my amps. So with slight over pannel I should be inside the limit on that Rover controller, the price is good at $144.00
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