bb_94401 wrote:
Vi = 14.5 at your alternator; d = 40 feet (20' out and 20' back); 8 AWG R = 0.0067056; I = 30A
Vo = 13.7 VDC (the typical float voltage @ 50F) little to no charging occurring
To achieve a 1% voltage drop and get Vo = 14.4 to get near a typical adsorption phase charging voltage, limits the current to 5A in 8 AWG wire.
Little wonder that very little charging goes on with 10 AWG wire, given the length of run when you combine the truck and TC wiring.
A flooded LA battery will charge at 13.7, just not as fast as 14.4. And if it is drawing the 30 amps causing the voltage drop, then it is charging at - you guessed it, 30A. That is why I think absent other problems, #8 is OK for a normally sized battery bank (200 AH). If you have 400 AH and want it charged quickly, then #4 or #6 would be better.
However if you are already drawing 30A for your fridge, then you are starting at 13.7 and dropping further to the extent that the battery is charging (and a battery at 50% charge will draw a lot, even at 13.7V). That is why I say fix the fridge problem so you don't have to run it on 12V. That makes everything more complicated.
