wire guage is fine - it's the VOLTAGE.
How about this one for recycling threads !?
Does anyone know if the 7 pin on 5th gen is wired to charge a trailer battery? The diagram on the cap doesn't show that pin to do anything but all the searches for it I've done say it should.
I took the teardrop out for the first time with my 4Runner and the battery died on it. Granted I had my fridge running overnight but usually if my battery is topped off it hasn't been an issue in the two years I've done it with my LR Disco.
I hooked the trailer up and ran the engine for a good while to see if it would get SOME charge and it didn't do much.
I'm out with it now and I didn't bring my volt meter like and idiot.
Not that it matters right now, this I can figure out once I get back but I'm bored and have signal
The 4R alternator has a built-in controller, and that controller uses a "sense" wire to adjust the Voltage (and Power) beign generated by the Alternator. Right when you start the SUV, it generates lots of amps, at high Voltage (~ 14.4V) to charge the 4R "starting" battery. But after a running for a while, while, it "sees" good voltage on the Sense wire - and drops the Voltage
a lot (my own 4R measures about 13.8V). 13.8V is insufficient to push a useful amount of power into a Lead-Acid Battery, it's a mere "float" Voltage level.
Next: Although the wire is AWG #10, (note: it's fused at 30A, anything smaller would be illegal); there is some voltage drop along the 20-30 feet of distance. (It varies according to current). Now turn on the Trailer's Refrigerator DC heater element, and think about what happens (In a Norcold N300.3, it's basically a 1-ohm resistor, pulling Amps equal to the Supply Voltage. Small Dometic models are similar.)
It pulls current from the "best" Voltage Source. The Trailer's "house" battery might be discharging at only 12.2V (~50% SOC), but if the circuit to the TV tired to pull more than about 6A - it would go lower than that. So more than half of your Fridge power is coming out of the Trailer "house" battery, even though it's already discharged to about 50%.
Titanpat57 is correct about the one possible solution: If you want to
charge the trailer battery, a big short wire (#8 or #6) between batteries would do it - because the 12.1V Trailer battery would "suck in" a lot of Voltage from the "starting" battery, dragging the "sense wire" voltage down - and provoking the Alternator to provide more power.
Somewhat expensive "voltage boost" machines (by "Redarc" of Australia, and 'Ctek" or Sweden) provide a nearly perfect solution, by pulling "lots of power" at lower TV Voltages (from 14+, all the way down to about 12.5, when they "disconnect" form the TV to protect the Starter Battery) through the Bargman, and they Boost it for your current battery State of Charge (typically 14.4V if it sees that "Boost" Mode is appropriate, dropping to 13.8 "Float" autromatically.)
