Solar wire size
I,m going to add another 100w panel to the camper and am not sure what size wire Lance used in 2011 12g or 10g it looks like 12g to me and if it is I will replace with 10g. Thanks for any help
Forum Discussion
I would suggest that you go to Handy Bob's site and read all his articles.
The RV Battery Charging Puzzle
Here's what he has to say on wiring:
*WIRING:* Resistance or impedance is the enemy. You have to overcome it and get the power to the batteries, not just to the output terminals on your charge controller. The system in my rig is efficient because I wired it with six gauge wire, for a total distance of only 12 ft from panels to controller. I ran #4 from the controller to the batteries. I spent about $30 for this wire and gained about $120 worth of added power when looking at what 6% of what my panels cost, which is about what I gained when going from 25ft of poorly routed #8 wire to 12ft of #6 wire. Big wire is even more cost efficient when you are looking at the difference in cost for a new installation. If your controller is located very close to the batteries like it needs to be, it will regulate the voltage to the batteries so they get what they need. You can run smaller wires from the panels to the controller than you run from there to the batteries, but make sure you can get nearly 16 volts minimum to the controller by looking at a voltage drop table. Big wire is cheap compared to the cost of panels, so err on the big side. You can either run big wire or install multiple smaller runs and split the panels up into several feeds. DO NOT tie the wires together at both ends. One wire will always have less resistance & carry more of the load. Find a voltage drop chart and limit your loss from the roof to the batteries to 3%. This way you can ignore the drop in the wires on the roof. You will find that voltage drop is directly proportional to the number of amps (higher amps equals more voltage drop), which is why you should wire for the number of panels you might need and not use the minimum size for the panels you initially buy. Use BIG wire, at least #8 for two panels and, and #6 for three panels and that is only for runs under 20 ft. I have installed a lot of #4 cable and wish I had it in my own rig.
From the controller to the batteries the wire size is critical. The
bigger the better. If you cannot design for less than a 1% drop due to the length of run, it is possible with better controllers (Morningstar Tristar & Prostar, plus a few others) to use remote voltage sensing and the controller will boost the voltage going out, so that the correct voltage reaches the batteries. Do not be tempted to use this as a way of installing smaller wires. Voltage drop in the run between the controller and the batteries equals wattage loss in charging. Fewer watts come out of the end of the wire than go in when the voltage drops. This means that using smaller wires here will cost you watts charging every day forever. This is a foolish place to save a few dollars.
A word on the stranded wire debate: Yes, you should use stranded wire
because it is better for DC power. However, the difference between
stranded building wire and finely stranded automotive or welding cable
is teeny, tiny electrically, so don’t obsess about it. The finely
stranded stuff is easier to work with, but the main thing to worry about is a UV rated shield on the roof, protection against damage when routing through the rig and the price. Buy what you can find at the right price and what you can deal with mechanically. There is nothing wrong with running big, stiff wires and then splicing short, flexible leads on the ends to make it possible to connect to terminals. The big wire is there to limit voltage drop, not to carry amps. You are not going to load it enough for the splices to get hot and fail.
The RV Battery Charging Puzzle
Here's what he has to say on wiring:
*WIRING:* Resistance or impedance is the enemy. You have to overcome it and get the power to the batteries, not just to the output terminals on your charge controller. The system in my rig is efficient because I wired it with six gauge wire, for a total distance of only 12 ft from panels to controller. I ran #4 from the controller to the batteries. I spent about $30 for this wire and gained about $120 worth of added power when looking at what 6% of what my panels cost, which is about what I gained when going from 25ft of poorly routed #8 wire to 12ft of #6 wire. Big wire is even more cost efficient when you are looking at the difference in cost for a new installation. If your controller is located very close to the batteries like it needs to be, it will regulate the voltage to the batteries so they get what they need. You can run smaller wires from the panels to the controller than you run from there to the batteries, but make sure you can get nearly 16 volts minimum to the controller by looking at a voltage drop table. Big wire is cheap compared to the cost of panels, so err on the big side. You can either run big wire or install multiple smaller runs and split the panels up into several feeds. DO NOT tie the wires together at both ends. One wire will always have less resistance & carry more of the load. Find a voltage drop chart and limit your loss from the roof to the batteries to 3%. This way you can ignore the drop in the wires on the roof. You will find that voltage drop is directly proportional to the number of amps (higher amps equals more voltage drop), which is why you should wire for the number of panels you might need and not use the minimum size for the panels you initially buy. Use BIG wire, at least #8 for two panels and, and #6 for three panels and that is only for runs under 20 ft. I have installed a lot of #4 cable and wish I had it in my own rig.
From the controller to the batteries the wire size is critical. The
bigger the better. If you cannot design for less than a 1% drop due to the length of run, it is possible with better controllers (Morningstar Tristar & Prostar, plus a few others) to use remote voltage sensing and the controller will boost the voltage going out, so that the correct voltage reaches the batteries. Do not be tempted to use this as a way of installing smaller wires. Voltage drop in the run between the controller and the batteries equals wattage loss in charging. Fewer watts come out of the end of the wire than go in when the voltage drops. This means that using smaller wires here will cost you watts charging every day forever. This is a foolish place to save a few dollars.
A word on the stranded wire debate: Yes, you should use stranded wire
because it is better for DC power. However, the difference between
stranded building wire and finely stranded automotive or welding cable
is teeny, tiny electrically, so don’t obsess about it. The finely
stranded stuff is easier to work with, but the main thing to worry about is a UV rated shield on the roof, protection against damage when routing through the rig and the price. Buy what you can find at the right price and what you can deal with mechanically. There is nothing wrong with running big, stiff wires and then splicing short, flexible leads on the ends to make it possible to connect to terminals. The big wire is there to limit voltage drop, not to carry amps. You are not going to load it enough for the splices to get hot and fail.
