POSITIVE GROUND - Not what you think it is.. This statement isn't referring to the battery connections, its referring to how the load shedding option is switched. The controller supplies the MINUS to turn something ON and OFF.
In a Negative ground, the controller would supply PLUS to turn something on / off,.
I bought a inexpensive Renogy 100 watt kit several years ago. The controller was a Positive ground. NO BIG DEAL
Here's why.
The controller gets wired to the solar cells and the batteries. The controller will charge and maintain the batters.
ALSO - the controller has another neat feature. The controller monitors the battery voltage, the solar cell voltage, and some will even have a time function. If the battery or cell voltage gets to low, or the timer is set for specific times, the controller can "shed loads". When the voltage comes back up again, it can turn the "loads" back on. It does this at the "LOADS" connection on the controller. Kind of like an internal switch.
The "Positive ground" is referring to this feature. specifically, how the "loads" connection is connected inside the controller. When the controller wants to turn a load on, it connects the LOAD terminal to the battery MINUS terminal.
You can use this feature in a "Negative Ground" system, but the load thats connected cannot be connected to the negative ground, otherwise it will be turned on all the time. The best example I can think of is something like a dash radio that has a metal case that bolts to the negative ground. This won't work, because the metal case will supply a MINUS to the radio all the time, even when the controller removes the MINUS.
However, if you wired a relay or a light bulb, or anything else that didn't have this hard connection to the minus, you could control it with this output.
Look at the link and read through it.
http://www.irv2.com/forums/f56/renol...nd-244437.html
I even did a hand sketched diagram on post # 19..