rickst29
04-05-2020, 10:32 AM
I am awaiting a few MC-4 connectors, which will allow me to shorten some over-long connecting wires which you see in the photo.
One panel is slightly larger and more powerful, with about the same amperage as small ones - but slightly higher voltage. The small ones are all "cheap 120W, 21 Volt" flex panels which I discussed in another Thread. They are all wired in series - constant current of the worst-performing panel, but with all the voltages added together. I suspect that the rated specifications are fake, and the panels are really about 100 watts each. They are configured as 9x4 cells, which is typical for 100 watt panels.
My MPPT charge controller can handle 150V of panel voltage. 23.0 Volts * 3 panels, plus 24.2 Volts * 1 panel = 93.2 Volts during "PWM Mode" disconnects. I would not !!! try this configuration with a charge controller of only 100V Solar Array Maximum Voltage, and it would instantly blow up some very small controllers (with Maximum Array Voltage of only 40-60 Volts). Those controllers would need panels wired in Parallel, so that Voltage would be constant (the lowest-voltage panel), and current would be added together from each panel.
The reason for "needing" 430 watts is not to actually get 430 Watts on a cloudless day in late June. Rather, it is camping in late Season (September, or even October), when the sun is at a much lower angle. And even in June, mounting panels flat on the roof does not match the angle of sunlight inclination.
On a perfect day in June, your Solar Controller also needs a good capacity to reject power which it does not want to "accept" for charging batteries and running instantaneous 12V loads. My somewhat small Controller (30A) is rated to handle attachment of 720 watts of maximum Solar power, even though it cannot use more than about 460 Watts maximum. (30A * 14.5V into the batteries, with 5% input power lost in the conversion. My batteries accept high charging voltages through the entire charging process).
- - - -
From the front shell roof, 10 AWG Solar Wire runs down the rear street-side lift arm for that shell, and then follows the frame towards the front of the TM, and inside the front-most frame crossbar (within the TM "box", not the towing A-frame). My Solar controller is mounted on the inside front wall, directly under the table (which I can no longer fold closed). From there, battery connections run sideways along the front and into my battery storage area - under the curb-side bench.
My batteries are LiFePO4, too valuable to leave out on the tongue. And they don't "like" cold weather, so I have put them into the interior storage box. (As far from the heater as possible.) When I had lead acid batteries, the battery wires simply went back out the front lower wall and into a tongue-mounted battery box. After drilling holes and pulling 3 wires (12V+ , Grounding Neutral, and Battery Temp Sensor), I filled the gaps and sealed the wires in place with 3M 4200 Boat Sealant.
- - - -
In theory, if I abandoned the larger panel, I could place a total of 5 smaller panels on the front shell. (4 across, plus the rear side.) But I'm not inclined to do that yet, because the current layout has been sufficient to meet my needs.
One panel is slightly larger and more powerful, with about the same amperage as small ones - but slightly higher voltage. The small ones are all "cheap 120W, 21 Volt" flex panels which I discussed in another Thread. They are all wired in series - constant current of the worst-performing panel, but with all the voltages added together. I suspect that the rated specifications are fake, and the panels are really about 100 watts each. They are configured as 9x4 cells, which is typical for 100 watt panels.
My MPPT charge controller can handle 150V of panel voltage. 23.0 Volts * 3 panels, plus 24.2 Volts * 1 panel = 93.2 Volts during "PWM Mode" disconnects. I would not !!! try this configuration with a charge controller of only 100V Solar Array Maximum Voltage, and it would instantly blow up some very small controllers (with Maximum Array Voltage of only 40-60 Volts). Those controllers would need panels wired in Parallel, so that Voltage would be constant (the lowest-voltage panel), and current would be added together from each panel.
The reason for "needing" 430 watts is not to actually get 430 Watts on a cloudless day in late June. Rather, it is camping in late Season (September, or even October), when the sun is at a much lower angle. And even in June, mounting panels flat on the roof does not match the angle of sunlight inclination.
On a perfect day in June, your Solar Controller also needs a good capacity to reject power which it does not want to "accept" for charging batteries and running instantaneous 12V loads. My somewhat small Controller (30A) is rated to handle attachment of 720 watts of maximum Solar power, even though it cannot use more than about 460 Watts maximum. (30A * 14.5V into the batteries, with 5% input power lost in the conversion. My batteries accept high charging voltages through the entire charging process).
- - - -
From the front shell roof, 10 AWG Solar Wire runs down the rear street-side lift arm for that shell, and then follows the frame towards the front of the TM, and inside the front-most frame crossbar (within the TM "box", not the towing A-frame). My Solar controller is mounted on the inside front wall, directly under the table (which I can no longer fold closed). From there, battery connections run sideways along the front and into my battery storage area - under the curb-side bench.
My batteries are LiFePO4, too valuable to leave out on the tongue. And they don't "like" cold weather, so I have put them into the interior storage box. (As far from the heater as possible.) When I had lead acid batteries, the battery wires simply went back out the front lower wall and into a tongue-mounted battery box. After drilling holes and pulling 3 wires (12V+ , Grounding Neutral, and Battery Temp Sensor), I filled the gaps and sealed the wires in place with 3M 4200 Boat Sealant.
- - - -
In theory, if I abandoned the larger panel, I could place a total of 5 smaller panels on the front shell. (4 across, plus the rear side.) But I'm not inclined to do that yet, because the current layout has been sufficient to meet my needs.