Basic Questions on Solar Install
I'm finally getting rid of the generator and looking to install solar. Right now I have a 2000W inverter and 450AH of lead acid batteries. I'm looking at installing (3) 175W panels and an MPPT charge ...
Forum Discussion
I can only say about what I learned in real life playing with my three 100w panels in my ground mounted set-up. I could easily swap back and forth putting them in series or parallel with an MPPT controller and with them in parallel I could swap between MPPT and PWM controllers, leaving all wiring as is. So I did.
I was also able to see how shading part of one panel affected the array by watching the shadow cross the panel and the Trimetric monitor when in series or parallel. So I did all that to see what really happens. the shadow did not conveniently do just one by-pass section at a time, but was at an angle that would get part of two sections, eg.
In full sun I got the same amps to the battery no matter which way I did it, series or parallel, and PWM or MPPT. MPPT did a little better in the shoulder hours, but I never saw the fabled better low light with them in series and a higher voltage. It is a good theory, but in low light solar is near useless anyway, so whatever.
On shading, it was better to have them in parallel. However it didn't matter much in my case because the shading was late in the day with the sun at a low angle. By then I already had most of the solar I was going to get that day.
In this case with the panels on the roof and shading from vent covers and the A/C shroud, and even the TV antenna, it could matter for more of the day with the sun higher. So parallel is my vote!
Note that you can use taller "legs" to mount the panels so they are not as low compared with the height of the vent covers. You can test for shading ahead of time by using cardboard "panels" at different heights and positions on the roof. If you can't escape shading completely, you can learn which way to park to get the most sun, if you have the option of which way to park.
I was also able to see how shading part of one panel affected the array by watching the shadow cross the panel and the Trimetric monitor when in series or parallel. So I did all that to see what really happens. the shadow did not conveniently do just one by-pass section at a time, but was at an angle that would get part of two sections, eg.
In full sun I got the same amps to the battery no matter which way I did it, series or parallel, and PWM or MPPT. MPPT did a little better in the shoulder hours, but I never saw the fabled better low light with them in series and a higher voltage. It is a good theory, but in low light solar is near useless anyway, so whatever.
On shading, it was better to have them in parallel. However it didn't matter much in my case because the shading was late in the day with the sun at a low angle. By then I already had most of the solar I was going to get that day.
In this case with the panels on the roof and shading from vent covers and the A/C shroud, and even the TV antenna, it could matter for more of the day with the sun higher. So parallel is my vote!
Note that you can use taller "legs" to mount the panels so they are not as low compared with the height of the vent covers. You can test for shading ahead of time by using cardboard "panels" at different heights and positions on the roof. If you can't escape shading completely, you can learn which way to park to get the most sun, if you have the option of which way to park.
