Amps needed from TV to TAB 320 S while towing

Lynnlee

I have 2016 TAB 320-S and a 2020 Subaru Outback XT. My mechanic is adding the wiring to the TV to make it a 7-pin harness. He wants to know what amperage does the trailer need from the TV while the TV is running. I know the trailer battery needs to charge (and perhaps run the 12v fridge) while driving. I also have electric brakes on the trailer. (However, I'm not sure if brake electrical use is included in this wiring.) The mechanic is adding the wire to charge the trailer battery and doesn't know the fuse size needed between the car and trailer. He is adding a wired brake controller, too.  Can you help?

dragonsdofly

@Lynnlee, most here recommend a minimum 10 guage DC wire for the charging line. Yes, the brake line is separate and has its own power requirements. The blade fuse your vehicle needs will be specific to your vehicle. Our 2005 gmc envoy xl uses a 15 amp fuse for the charging line, but our 2015 chevy Silverado 2500hd has a 20 amp fuse on the charging line. That is because the newer vehicle has a larger, higher output alternator. This again, will depend on the specifics of your tow vehicle. -Denise

ChanW

Ours uses a 30A self-reset circuit breaker in the TV. 

Recommend 8ga-10ga wire to have any hope of keeping up with the 3-way fridge (it needs 11A on 12v mode).

Not sure about Subaru, but the amperage that your TV provides will also be limited by the TV's charging system. Modern alternator systems are regulated by the computer, and will limit the power output to the minimum needed to charge the TV battery in normal conditions (It helps with their fuel mileage rating).

So your alternator might be fine for simply maintaining a charge on your battery, but might not put out enough for the fridge.

There's quite a bit of chatter here in the forum regarding this. Search for "charging" or "charge wire" or "alternator".

Lynnlee

Thanks for the quick response! I'm soon on the road:)

Sharon_is_SAM

@Lynnlee - most TV alternators effectively function as a trickle charger and deliver limited amps to the TaB battery.  If you tow with the 3 way frig on DC, you risk arriving at your campsite with a depleted TaB battery (depending on distance/time to campsite).  On the DC setting, you can not regulate the frig temperature setting and it draws a constant 11 AHr. Many owners will either run their frig on propane or turn it off completely and stuff it with frozen water bottles to maintain the chill.  I think the best you can do is optimize what charge gets to your TaB battery and reduce voltage loss by using the largest wire possible as Chan referenced.

BrianZ

Our TV 7-way 12V+ line is wired directly to the TV battery via a 30A self-reset circuit breaker installed near the TV battery.  So, it's always hot - something we have to keep in mind regarding unplugging it for an extended stop while hitched, to avoid draining the TV battery.  Our hot wire was installed through the T@B dealer where we purchased, by a Leonard's shop who routinely does that & brake controller installation for the dealer.  We turn off our fridge for travel though, so generally not an issue.