Originally Posted by Martin J
Thanks for the comments. In my case panels were 1$ a watt 4x235watt $940 plus the Midnite controller $550. I went for the midnight over the blue sky I had beforebecause the functions were better and ease of use. It takes up to 150vdc in and up to 96volts out for 72 volt systems. I run mine at 48volt in and 12volt out. The 48volt means the wiring is very light 4g or 6G if i remember. More than adequate for the amperage I create. My main criteria was to fully utilize all power, and enable me not to waste the shoulder periods of dawn and dusk.As we spend considerable time 3 monrths cruising in the spring and 3 months cruising in the Autumm in the Caribbean power is very important and has to be self managing. Since installation on this boat the last 3-4 years have been maintenance free, apart from a self watering battery bank! As an after thought I do have a standard PWM on my jeep running the solar panels that keep my Jeep operational at the airport while we are in the caribbean!! Even when we return in early January the jeeps charged and ready to go!!
One major thing is the saving in heavy cables , and runs to use the variable voltages of an MPPT
Well thought out system!
I do want to comment on heavy cables that many believe are necessary in 12 volt panel wiring.
Batteries in need of charge have low terminal voltages even when accepting a charge. The important thing to notice is the voltage/current curves for the panels in use and calculate the voltage that the panels will see....battery voltage under charge plus the wiring voltage drop. The time when most current will be accepted by the battery is when it is in a lower charge state so some wiring voltage drop can be accommodated. As the charge increases, the acceptance current decreases which reduces the wiring voltage loss.
Now of course this does not suggest one can use lamp cords for panel wiring. It illustrates only that lesser size wires can be used in many cases and that is all.