Voltage vs. PWM controller & wire size
Ok, there is a recent thread out there MPPT vs. PWM and some post were a little confusing to me. Instead of hijacking his thread I started a new one. My set up is two 208 watt Sony panels with 28....
Forum Discussion
Calkidd wrote:
My set up is two 208 watt Sony panels with 28.71 volts (I.E. 24 volt panel) which is 14.5 amps. (V * A = Watts).
I take that to mean 416W total. With PWM you'll get the panels Isc or about 2x7.4 = 14.8A, ie losing the power associated with the higher voltage. With MPPT you'll get 416W/14.4V = 28.9A, minus some controller loss, so say 25A+.
I read Handy Bob's information and other research about wire size. Ok, I get that, but if 10 ga works why in the hell are people using 8 or even 6 ga to run their solar panels when the loss is 2-5% with 10 ga? After doing the voltage drop calculations with my system with a run of 30 feet (being very liberal here) I only have a 3% loss of voltage.
Wire losses are dependent upon both the amps and voltage and other factors. With higher MPPT amps per above the % loss is higher, hence larger wire is needed to reduce the loss.
Also, why are some using 1/0 ga for inverter and battery wiring? HOLY ****! We are talking about a cable that can handle 150 amps. Tell me what 12 volt load could anyone be possibly using in an RV that produces that much amperage? Wouldn't 2 ga be just fine?
MW are the prime example. Some even run a small A/C.
For a given load a smaller cable can be used if the distance is short. My charger/inverter uses 4/0 ga cable. My solar controller uses 4 ga for 50A maximum.
