Parasitic Draw on RV?
I am getting ready to add a small solar system to the top of my 5er to keep the batteries topped off when we leave the camper at the lake for extended periods. My wife and I generally pull the camper ...
Forum Discussion
BFL13 wrote:
The voltage on the controller to array wires is battery voltage with PWM, so voltage drop importance is not so clear to me. You do want the amps though.
With MPPT on the controller to array wiring, voltage drop is important because it affects the "watts in" to the controller, which then has "watts out"
1. I understand that as long as the V-drop doesn't cut below your desired voltage on the battery, it's all good. Then at some point it suddenly becomes not good at all. Series PWM installs without roof junction box are typically limited to 300W, with higher wattage people use wire #6 or better and need a J-box. Some pain... 400W with #8 "might" still let him get away without J-box.
2. Voltage drop with MPPT with RV-sized array of 24V panels is more of an academic point, it does exist but of very low importance. I run the numbers when deciding on whether to use #10 or #8 with 500W in series, and the difference on 60-something ft was 0.5% at max output. Literally a couple amp-hours a day, since most of the time it is below the max current.
Higher MPPT losses with higher voltage - that Piano mentioned - are more important.
