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
johnm1 wrote:
2oldman - I assume the panels could be rewired and the CC that comes with it is "Automatic recognition of 12 V/ 24 V". However (this is one area that I really don't understand) - the panels are listed as 12v but from the spec sheet it shows ...
Open circuit voltage (Voc) : 22.4 V
Optimum operating voltage (Vmp) : 17.8 V
so ... is it 12, 17.4 or 22.4v?
depends. with no load attached the panel will read 22.4V in direct bright sunlight.
When hooked to a MPPT controller in bright sunlight, the controller will load the panel enough to drop the voltage to Vmp, 17.8V and Imp and then convert that to DC a battery charging voltage and current, between 12V and 14.8 or so depending on charging sequence.
load the panel with a very low resistance, near short circuit and the and current will be near or at Isc in bright sunlight.
Panels are a voltage limited current source device in most of the operating range, that is the current remains constant regardless of load voltage. that's where you want the panel to operate.
Actual panel voltage depends on the type of controller used, the load the panel sees, the amount of light hitting the panel.
In general panel voltage will be in the 12V-Vmp range, the voltage at the battery will be determined by the type of controller and the mode the controller is in and the battery state of charge.
Once the battery is charged, either a PWM or MPPT controller will only supply the current needed to keep the battery fully charged.
