Initial information gathering to increase solar on roof

[Bobbo]

Please excuse me because I know less than nothing about solar.

When I bought my Airstream TT in 2017, I had the dealer add the factory solar package. It included one 80 watt solar panel (brand unknown, whatever Airstream uses), one PVCM25D controller from Atkinson Electronics, and a pair of AGM Group 24 batteries.

I am going to get the dealer to increase the solar. I am either going to:

1. add 2 more 80 watt panels in parallel. I know this will work because the controller says it will handle 25 amps, and the 3 panels will be less than that.

OR

2. add 1 more panel wired in series with the current panel, and add 2 more panels wired together in series, then wired in parallel with the first pair. This will double the voltage to the controller, while reducing the amperage to less than option 1 above.

Further information - it would be very difficult to replace the 10g wire from the roof of the TT to the controller. I think (I haven't opened the compartment yet) that it would be easy to replace the 12g wire from the controller to the batteries.

Can this controller handle both of these scenarios?
Is there a significant advantage to replacing the controller?
Is there a better option that I have not considered?

Any and all suggestions are welcome.

[Bobbo]

I have come up with 4 potential setups and want to know if anyone sees a problem with any of these options. I am also interested if one of these options is better than the others. On all of these, I will be replacing the fuse on the 10g wire from the panels to the controller with a 20 amp or 30 amp fuse, and replacing the fuse on the 12g wire from the controller to the battery with a 20 amp fuse.

1. Keep my PVCM25D controller, which is capable of outputting "25 Amps @ 28V DC." Install a total of three 80 watt panels in parallel.

2. Keep my PVCM25D controller. Install a total of four 80 watt panels with 2 pairs of panels wired in series, and those two series in parallel.

3. Replace my controller with a Renogy Commander 20 amp MPPT controller. Install a total of three 80 watt panels in parallel.

4. Replace my controller with a Renogy Commander 40 amp MPPT controller. Install a total of six 80 watt panels with 3 pairs of panels wired in series and those 3 pairs wired in parallel. I would have to change out the 12g wire from the controller to the batteries with an 8g wire fused at 50 amps.

Like I said above, I am trying to dig into the specifics of exactly how to wire this up now.

[Lwiddis]

So AS cut corners on the wiring and the installing dealer cut corners on the controller? Not surprising.

[Bobbo]

2oldman wrote:
Haven't we already done this?

It's difficult to find the specs on that controller, but it's a pretty cheap one.

Yes, but at that time I had no clue what controller I had. Since I have dug out the documentation to find that out, I thought it was time for more specific information.

Here is all of the documentation that they provided with the controller: PVCM25D Solar Controller.

I am open to changing out the controller if someone will recommend a decent one. We are definitely part-timers, so we will either go 240 watts as 3 of the 80 watt panels in parallel, or 320 watts with 2 parallel sets of 2 panels in series.

I have contacted Airstream about their solar package, and they said:

Airstream wrote:
The solar panel is made by a company called Zamp. Our part number for the solar panel is 513047-01, but you would have to order and get pricing from an authorized Airstream dealer. Zamp’s part number for the panel is USM1007.

However, looking at their website, I have my doubts that the dealer used the Airstream package. He may have bought a third party unit and installed it, hence the cheap controller.

[red31]

I don't care for this type of controller, On @ 12.7VDC, Off @ 14.2VDC (flooded)
On @ 12.4VDC, Off @ 13.9VDC (sealed). Repeated undercharge.

http://www.aurorapower.net/pdf_reference/Electrical/Atkinson/PVCM25D.pdf

[naturist]

I just bought a kindle book on mobile solar that I can recommend highly. Mobile Solar Power Made Easy.

[Lwiddis]

All the money AS charges for their TTs and they cheapout on solar wiring...10 and 12. Since you can’t replace the wire, I vote for four 80 watt panels series/parallel and an MPPT controller. Do an energy survey but I think 320 watts will be sufficient. 300 does it for me.

[2oldman]

Haven't we already done this?

It's difficult to find the specs on that controller, but it's a pretty cheap one.

[pianotuna]

Hi,

You would need to upgrade to an MPPT controller if you go the 2nd route. However, that is what I would do. (and did do when I installed solar, for the exact same reasons of #10 prewire).

If you full time 360 watts is unlikely to be enough to eliminate generator use. I would replace the OEM panel and go to 600 watts in series/parallel.

If you part time, 240 watts is a good fit.

This series of articles may help: https://freecampsites.net/adding-solar/