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Cable Length questions

johnpitts01

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Oct 16, 2019
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Looking to convert my Truck Camper system from FLA to Lithium batteries.
The camper also has solar.

The factory install has different positive and negative cable lengths from the solar controller to the battery. The positive cable I estimate to be @ 15' length. Negative Cable @ 10'.
Is this ok?

It is possible to move the solar controller much closer to the batteries. I can get the solar controller within @ 24" of the batteries.
What are the advantages of moving the solar controller closer to the batteries?
 
Lengths of positive and negative cables for PV panels can be different, no problem.
Shorter is better, but unless you have many panels in parallel, current from PV panels isn't high and length of wire on a camper won't matter. If the panels are in series, that keeps voltage high and current low. In series, something like 12 awg is fine. If you parallel multiple panels, depending on the current you may need thicker wire.

If you have several panels, current from charge controller can be significant. 700W of panels and 12V battery would be 60A. Wire should be thick, probably 6 awg in this case. SCC close to battery reduces power loss and lets SCC see battery voltage more accurately.
 
thanks for the replies.
My system is not perfect nor optimized. Came from the factory with (1) 100 W panel. The dealer talked us into adding a second 170W panel before I knew anything about solar. The panels are wired in parallel. Factory wire is 10 gauge stranded copper.
 
Solar panels to charge controller should be fine with 10 awg. I thought your question was about CC to battery. The CC will need be adjusted to charge Li battery. Much different than lead acid.
 
Zil apologies if I've confused the discussion. Yes my question is about CC to the battery. in my TC that wiring is 10 gauge stranded copper.
 
100 + 170 = 270W
270W / 12V = 22A
10 awg is fine for 22A. If it had been a very long run could add up to excessive resistance and voltage drop, but not a problem in a vehicle, SCC to battery.
Voltage from PV panels is a bit higher, current a bit lower, so ok there too.

You could go through the exercise of looking up ampacity (maximum current depending on temperature rating of insulation) and resistance, calculate voltage drop and power lost. That's useful for other circuits like inverter to battery wiring as well.
 
Looking to convert my Truck Camper system from FLA to Lithium batteries.
The camper also has solar.

The factory install has different positive and negative cable lengths from the solar controller to the battery. The positive cable I estimate to be @ 15' length. Negative Cable @ 10'.
Is this ok?

It is possible to move the solar controller much closer to the batteries. I can get the solar controller within @ 24" of the batteries.
What are the advantages of moving the solar controller closer to the batteries?
I've done this upgrade with my Lance truck camper. I wanted to move my MPPT controller closer to the battery but it would have required a lot of rewiring.

What kind of camper do you have? I'd be happy to share what I learned along the way.
 
The charge controller regulates voltage at it's output terminal. The wires voltage drop to the battery will throw it off, more current, more error, slower charging. I would suggest the largest gauge your controllers battery terminals can handle, and short as reasonably possible.
Don't forget that circuit breakers and fuses add a little milli ohms too.
There are voltage drop calculators out there. calculator
Victron may be an exception. They have a battery voltage sensor that bluetooth connects to their charge controller.
 
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