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....
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The simple answer is that with PWM the panel wattage is not what drives the system. You have to look at the panel output current (Isc) which for your panels would be about 7.24 amps each. You can look at your panel's IV curve and check where your battery voltage intersects the curve. So at the best of conditions you have 14.5 amps available to you. Add in wiring losses and you can see that things go down hill rather quickly.
Watt output IS the driver for an MPPT system as wattage in equals wattage out minus losses. Voltage loss from inadequate wiring and panel voltage degradation due to panel cell temp are the biggest killers for the MPPT system.
It's true that for a PWM system, wiring losses from the panels to the controller are not as critical as for a MPPT system. However voltage drop for an inverter is critical at the high amp draw as voltage loss is proportional to amperage. This will cause the inverter to operate poorly and introduce premature low voltage shutdown.
Your panels are kind of in no man's land for RV use. With PWM there is considerable waste, but the Voc is too low to derive much benefit from a MPPT controller, but you would probably get on the plus side of 20 amps from your system. Of course if the controller can handle the voltage you could run the panels in series and on a good day could see 28 amps.
BTW, running the microwave will get you close to 150 amps. On high draw circuits it's not about ampacity but all about voltage drop.
Watt output IS the driver for an MPPT system as wattage in equals wattage out minus losses. Voltage loss from inadequate wiring and panel voltage degradation due to panel cell temp are the biggest killers for the MPPT system.
It's true that for a PWM system, wiring losses from the panels to the controller are not as critical as for a MPPT system. However voltage drop for an inverter is critical at the high amp draw as voltage loss is proportional to amperage. This will cause the inverter to operate poorly and introduce premature low voltage shutdown.
Your panels are kind of in no man's land for RV use. With PWM there is considerable waste, but the Voc is too low to derive much benefit from a MPPT controller, but you would probably get on the plus side of 20 amps from your system. Of course if the controller can handle the voltage you could run the panels in series and on a good day could see 28 amps.
BTW, running the microwave will get you close to 150 amps. On high draw circuits it's not about ampacity but all about voltage drop.
