Solar Pannels

[gojodo]

This is probably the blind leading the blind but as I understand it the important rating is the Controller being rated 12V or 24V not the Panels. The panels send down as much voltage as they can collect and the Controller regulates the voltage that reaches the batteries. I think you may be right on a pair of the T 105's having around 225AH. The difference in 36 vs 44 cells is the panel sends down higher voltage from a 44cell panel given the same amount of sun light thus the Controller sends 12V at a higher amperage to the batteries. To answer your main question, I mounted my panels directly to the rubber roof using screws long enough to reach the wood sub-roof. Also you want to use Dicor Adhesive caulk before and after you screw the mounts to the roof. As far as tilt, my panels have a brace that can be added to raise one side of the panel to 30 degrees or so if you need to face lower in the Southern sky. Of course I DON'T drive with them up. The mounting brackets are simply four small corner brackets to which you then screw in the panel. Hope this answers your questions. If you need more expert advice contact Jack Mayer, I gave you his web page. He really does know how this stuff works. John

[7.3Ford]

quote:Originally posted by gojodo

If you need more expert advice contact Jack Mayer, I gave you his web page. He really does know how this stuff works. John

Thanks for you help John, and yes I found Jack Mayer site to be very helpful.

[ols1932]

quote:Originally posted by 7.3Ford

Nop series. If I end up with more than 4 panels (ie six 24v), then would wire them in as both series and parallel (ie 2 sets in parallel of three in series). They way I under stand it, with MPPT controllers (Outback FLEXmax at least), you want a high voltage, so the MPPT control has more to work with to maintain the 12V output and max current output on less than optimum days. The higher voltage also allows less voltage drop and less current, so you can use smaller wire.

If I am reading thing wrong, please straiten me out.

Far be it from me to say you're misreading something wrong because I don't know. All I know is my four panels are installed, wired in parallel. I have the HPV 22 controller which controls the charge going to my batteries. Been this way for almost seven years. Did I install mine wrong? Or rather, did John Palmer Enterprises install them wrong? I'm not the expert but I do know some who say they are experts and then those who really are experts. I may be completely misreading what you are doing so don't go by what I'm saying. Go with what you know to do.

Orv

[7.3Ford]

quote:Originally posted by ols1932
Far be it from me to say you're misreading something wrong because I don't know. All I know is my four panels are installed, wired in parallel. I have the HPV 22 controller which controls the charge going to my batteries. Been this way for almost seven years. Did I install mine wrong? Or rather, did John Palmer Enterprises install them wrong? I'm not the expert but I do know some who say they are experts and then those who really are experts. I may be completely misreading what you are doing so don't go by what I'm saying. Go with what you know to do.

Ovr,

Your systems is correct for the solar controller you are using. But after reading Jack Mayer site, I discovered there is a more expensive type of controllers out there now, called MPPT (Maximum Power Point Tracking) Charging Controllers. The OutBack FLEXmax will take input voltage up to 150VDC and output 12, 24, 36, 48, or 60VDC. Using the high voltage allows the controller to compensate for low output days, and keep a constant 12VDC going to the batteries.

[ols1932]

quote:Originally posted by 7.3Ford

Ovr,

Your systems is correct for the solar controller you are using. But after reading Jack Mayer site, I discovered there is a more expensive type of controllers out there now, called MPPT (Maximum Power Point Tracking) Charging Controllers. The OutBack FLEXmax will take input voltage up to 150VDC and output 12, 24, 36, 48, or 60VDC. Using the high voltage allows the controller to compensate for low output days, and keep a constant 12VDC going to the batteries.

The HPV 22 is an MPPT Controller and it will take whatever amperage there is coming down from the solar panels and will multiply it. How it does it I don't know. I just know that on good days, I have as much as 24 amps being outputted by my four 44-cell panels.

Orv

[gojodo]

This is interesting. As I understand it, if you wire two 24v panels rated at 6Amps together in series, you would theoretically have 48V sending the 6 Amps. to the Controller which can reduce the voltage to 12V and send on the resulting amperage to the batteries. If you were to wire the same panels in parallel then you would have 24V sending 12amps to the controller which would convert the voltage to 12V and send the resulting amperage to the batteries. Help me understand, assuming you are using a panel with 24V or higher what is the difference in how it is wired given the fact that the controller changes everything to 12V. John

[mopar1]

Solar panels, to me, are a kind of double edged sword. The camper always has to be parked in the sun so they can generate power. But the system can't run the A/C so even on mild temperature days it can get kind of hot inside. So then the generator has to be running to run the A/C. A big enough one can do the A/C and charge the batteries at the same time.
Now if the panels were mounted on something that can be put in the sun while the camper was in the shade would be nice. But then they would have to be assembled and disassembled and stored when traveling.

[7.3Ford]

quote:Originally posted by gojodo

This is interesting. As I understand it, if you wire two 24v panels rated at 6Amps together in series, you would theoretically have 48V sending the 6 Amps. to the Controller which can reduce the voltage to 12V and send on the resulting amperage to the batteries. If you were to wire the same panels in parallel then you would have 24V sending 12amps to the controller which would convert the voltage to 12V and send the resulting amperage to the batteries. Help me understand, assuming you are using a panel with 24V or higher what is the difference in how it is wired given the fact that the controller changes everything to 12V. John

Two things you need to worry about, volts and amps. Volts being what the maximum volts the wire insulation is designed for (usually >= 600volts), and current (amps). Amps is the driver for wire size, the more amps the bigger wire you need. Also the higher the amps vs maximum amps for a given wire size, the more voltage drop going thru the wire. Watts = Volts X Amps, so if you have 200 Watts at 24v, you get 200 / 24 = 8.3A, 200 Watts at 48v gives you 200 / 48 = 4.16A. Most panels have 15a and 600V maximum that can go thru the panel.

So if you are using 10AWG wire and 24v, that max Watts you can run is 720 Watts. So if you want more watts, you have to go to bigger wire or wire them in series (or series/parallel). So with the same 10AWG wire you can run 48V X 30A = 1,440 watts or even 96V X 30A = 2,880 watts. The other thing to look at is the open voltage of the panel, which is higher the than loaded voltage. You don't want to exceed the maximum volts of the controller when wiring in series. Most 24v panels have a 33VDC open voltage (33 x 4 = 132VDC), and since the OutBack controller I am looking at has 150VDC maximum, 4 panels in series is the maximum you want to use, and still have a margin for error. If I were using six 24v panels, I would wire two sets of three in series (72VDC) and parallel the two sets (which would also double the currents).

The HPV-22B has 22 Amp Charging Capabilities (Regulates up to 400 watts of solar input), and the HPV-30DR has 30 Amp Charging Capabilities (Regulates up to 600 watts of solar input). This means that you need 1.5 to 1.6 more watts input for a give watts output. This allows the controller to product rated output when the input (solar panels) are not putting out rated output. Plus controllers have efficiency ratings of 80-95%, so you lose some there also.