Handy solar info for lead acid batteries
Handy Bob
Forum Discussion
PT, I don't know what you and Salvo are on about, but for instance, my 255w panel mounted out on the grass away from the trailer on a tilted up contraption with lots of breeze off the ocean, was 50C with 25c ambient, where I measured using an IR gun gizmo pointing up underneath a foot away from the white backing. At 30+C I saw 55C panel underneath.
BTW the panel temp varies where you aim the gun. Sort of varies side to side and up to down. I couldn't solve that by swapping the panel end to end either. Might be an E-W thing, don't know. Anyway, that means each cell is at a different temp so its voltage will be different and the panel voltage is the result of all that added up.
Since PWM uses Isc, which does not go down with temperature, you don't care about panel temp with PWM, but it hurts MPPT big time. There you use input watts and output watts divided by batt V to get charging amps. That means a higher panel temp lowers panel V and so input watts and so charging amps in turn.
BTW the panel temp varies where you aim the gun. Sort of varies side to side and up to down. I couldn't solve that by swapping the panel end to end either. Might be an E-W thing, don't know. Anyway, that means each cell is at a different temp so its voltage will be different and the panel voltage is the result of all that added up.
Since PWM uses Isc, which does not go down with temperature, you don't care about panel temp with PWM, but it hurts MPPT big time. There you use input watts and output watts divided by batt V to get charging amps. That means a higher panel temp lowers panel V and so input watts and so charging amps in turn.
