Charging Battery with TV

DanL

I have a 2019 Jeep Cherokee as a TV which has an A/C outlet in the cargo area.     I was wondering if there is any problem with plugging a battery charger into the TV A/C outlet and connecting to the T@b400 battery to charge the trailer battery.    I would leave the TV engine running as to not discharge the TV battery.    I don’t know if there is a technical reason why this would not work or how long it would actually take to charge the battery using this method.     Any comments would be appreciated.    Thanks!

Sharon_is_SAM

Do you have a built in inverter?

WilliamA

If memory serves, the Cherokee inverter is 150 watts.  Also, you are converting 12V to 110V and back to 12V.  ?  Loss would equal output.  12V to 12V is 5 times more efficient.

WilliamA 

4ncar

I have the same, I believe the outlet has a. 900watt Max spec. So depends on what your battery charger uses... use the GC has a built in inverter.

webers3

The inverter on Jeep Cherokee is 150Watt max @WilliamA indicated, why wouldn't you connect the T@B via the 7 pin connector to the TV? That's what I do with my 2019 JC, charges whether I am driving or parked with engine running.

4ncar

Ya, he did say 150, didn’t he! What was I reading?

ScottG

There's some debate as to how effective using 12V DC from your T/V is for charging your T@B battery. Individual results may depend on the vehicle, generator output, charge line gauge, etc.

I'm no expert on the topic, but I can't see any reason why plugging a small charger into your T/V inverter would be any different from plugging it in anywhere else. Only thing is, depending upon how long it takes to get a full charge, you might be running your T/V for quite a while. All that gas might eventually pay for a small solar panel.  ;-)

Cbusguy

Too many variables to begin to guess.     First the how long depends on the charger you are using....is it a 3 amp or a 30 amp....then will your 150 watt inverter support it without blowing the fuses or burning itself up.  

The next is what is the output of your alternator at idle?   most alternators do not put out full current at idle,  just a small portion.    you might end up with a dead battery on the TV.


a bit of perspective......if you use a three amp charger on your depleted 100 amp hour battery it would take 30 hours of idling to recharge it.   

I intend on doing something similar,  but only when changing locations.   I have upgraded my alternator to a power bastards  alternator 250 amps and 125 amps at idle.    I figure I could get 1000 amp hours into my batterys over the course of a day driving.    

WilliamA

Forgive me if I beat a dead horse here.  I think that there are many sources of disinformation as relating to the charging line from trailer to TV.
First, an alternator puts out current independent of its rpm's.  It puts out amperage in proportion to the input voltage to the rotor windings.  Most modern alternators are capable of big (40-50A and over) power at idle.  The only impediments are engine hp and voltage input.  Voltage input is commonly managed by both the regulator (internal) and ECU.  It's safe to say the ECU will limit input voltage to the alternator based upon software that is designed to maximize mpg's and engine idle characteristics as well as heat management.  I'd bet a buck that pretty much any modern auto is putting out enough amperage even at an idle to make your trailer battery dance.
As I've preached for eons, the primary source of poor charging performance of the trailer charging circuit can be traced 90 times out of 100 to the wiring between the TV and trailer, more specifically, the ground circuit.
Folks run dedicated cables from the TV battery to the charging line on the trailer as a matter of course.  10 gauge is a common size for that.  But the most important and overlooked wire is always the ground.  Many OE trailer harnesses have 16 or (horrors!) 18 gauge wires for lights.  Okay.  Few SUV's come with factory 7 way harnesses.  So tap the 4 way harness for lights and add a brake and charging line! Right?  The 4 way harness is where the ground resides and is not equipped to handle the amperage.  Let's remember that the dedicated hot line for your charge circuit must be sized to handle 20-30 amps.  Fine.  But the ground circuit must also handle that same 30 amp potential....plus another 10 or so for brakes.....and another 10 or 15 amps for lights.....the entire amperage load of ALL combined circuits must return to the TV on 1 wire.  The ground.  95% of all trailer grounds come back to the TV and terminate through a  sheetrock screw in a fender panel.  Wrong.....
Do yourself a favor and try a simple test: get a 10 gauge ground wire (white or black) and run it directly from the TV battery ground to the trailer ground.  Assuming you have a 10 gauge hot wire you'll see your charging voltage increase by 10% and the amperage go up by 50%.  
I have been pulling teardrops for 3 years using dedicated 10 gauge ground lines from the TV 7 way to the battery.  I can charge my battery at the same rate my TV battery charges. Allowing for absorbtion differences between the automotive battery and its deep-cycle cousin, they should (and will) charge at exactly the same rate and amperage.  
Whenever you put 2 (or more) batteries in a parallel circuit together, the regulator will essentially "see" an average of the state of charge between them and respond accordingly.  If your trailer battery is much lower (voltage) than your TV battery, it will draw power from it.  That in turn will prompt the alternator to produce more power, again, within the parameters of the regulator and possibly, the ECU software.
Ground wire, people.  Ground wire.  It's not your alternator.....

WilliamA 

Cbusguy

That is why a battery isolator is a good idea.   This is my intention to use one of these.   Link

DanL

Thanks for all the comments and information.    Much appreciated!