Ask PYS: Power

Barry – Choosing a Solar Panel, on Aug 13, 2014 asked:

I am looking to buy solar panels and leaning toward a pair of the SP-112Q-JB. However, can you explain the difference between those and the “standard-output cells” equivalent size panels SL90Q-JB. In my Catalina 400 with the fridge and freezer (I don’t run it super cold) I burn through about 120-160 Ahrs in 24 hours. My house bank is 6 X T105 Trojan’s with a total capacity of 630 amps of which I’m assuming a maximum draw of approximately 300amps – my starting batteries are a pair of 4D’s which is only draw to stretch out that extra night if needed.

The difference between the SP112Q and the SL90Q is wattage. The SP model offer more wattage per are then the SL model. Our own daily Amp-hour usage is very similar to yours. We use about 150 AHrs of power a day. In order to provide as much power as possible, we opted to install the SP model instead of the SL. If possible, try to fit 3 panels at 112 Watts. This will provide you with a 336 watt solar array. From this you can expect 65 to 100 AHr of daily output on a sunny day.