Forum Discussion
12thgenusa
May 03, 2013Explorer
HiTech wrote:
For efficiency per dollar (useable watts and amps to the battery per dollar spent) we are approaching the point that PWM on a 24 v panels using just their Isc (not their full watts) may yet be the least expensive alternative since we have high voltage PWM controllers with large amp capacity for cheap. The race is between that and inexpensive MPPT controllers with significant wattage.
Jim
I don't see how this can possibly be true. Take my situation for example:
2 185-watt panels plus shipping - $613
1 MPPT Rogue controller - $325
(613+325)/((2*185)*.95)=$2.67 per watt to the batteries (352 watts)
or
2 185-watt panels plus shipping - $613 (Isc of 5.54 each)
1 PWM controller - $50
(613+50)/((2*5.54)*14)=$4.27 per watt to the batteries (155 watts)
That's if you can get a PWM controller that will do this for $50 and if the output voltage could stay at 14v (most of the time it will be less). If the controller was free it would still be nearly $4 per watt.
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