Portable (suitcase) solar "install" question
I've gone back and forth on solar panels on the roof or portable. Well, due to a tight budget, portable is the only way I'm going to get solar for now and it makes sense for me to try it out 1st as we...
Forum Discussion
geerally A 12v panel can operate over a range of near 0v to 20+v, their peak power is @17-18v. When heated from the sun, varying light these values change so there needs to be overhead (above batt voltage) for when light is low and the panel is hot (both lower peak power voltage). additional overhead is needed for voltage drop in the LONG wires from the panel to controller. Look at the graph previously posted, the 1000 line is spec for a 50w panel, two in parallel will still have the same Vmp and Voc but the current will be ~6A instead of 3A.
Note the 600 line, its current is 60% of the 1000, this is why one can add up all the sun that hits a panel in a day and multiply that by Imp or Isc to estimate ah available for charge/use.
I think of panels as magic when they match batt voltage. Your batt is at 12v, so is the panel, as the batt gains energy it voltage rises as does the panel. Once the batt reaches a set pt of say 14.6v the PWM controller goes to work. It disconnects and reconnects the panel at a high freq, the connect time will become less and less as the current to maintain the 14.6v becomes less as the batt gets FULL. This absorption mode generally lasts 2 hrs (controller controlled) and then a new set pt called float say 13.4v is now maintained in the same fashion.
Varying sun light, usage ... causes the controller to constantly be changing the on/off time to try and maintain the current set pt/mode. If usage causes the batt voltage to drop enough, the cycle starts over as it does each morning.
Note the 600 line, its current is 60% of the 1000, this is why one can add up all the sun that hits a panel in a day and multiply that by Imp or Isc to estimate ah available for charge/use.
I think of panels as magic when they match batt voltage. Your batt is at 12v, so is the panel, as the batt gains energy it voltage rises as does the panel. Once the batt reaches a set pt of say 14.6v the PWM controller goes to work. It disconnects and reconnects the panel at a high freq, the connect time will become less and less as the current to maintain the 14.6v becomes less as the batt gets FULL. This absorption mode generally lasts 2 hrs (controller controlled) and then a new set pt called float say 13.4v is now maintained in the same fashion.
Varying sun light, usage ... causes the controller to constantly be changing the on/off time to try and maintain the current set pt/mode. If usage causes the batt voltage to drop enough, the cycle starts over as it does each morning.
