Charging the Battery from Subaru

slotaichi

On a recent trip, I drained the battery.  I thought I could just plug the TAB into my car, start the car, and let it run for an hour or so.  But the battery died after a few minutes.  I thought it would fully charge during the 6-hour drive home but again, the battery died after a few minutes.  I went onto a Subaru Forum and discovered the voltage regulator will not provide the required charging voltage.  A suggested solution is to turn on the headlights.  Apparently, the voltage regulator adjusts voltage depending upon the load on the electrical system.  If there is no load, the default is 12 volts.  With the headlights on, the output increases to 14 volts.  I haven't tried yet but hopefully it will work.

jgram2

@slotaichi Welcome to the T@B forum! Did you have the T@B battery cut off switch turned on? What year/model is your trailer and do you have the 3 way fridge?  If a 3 way, did you have it on DC power while traveling?

dragonsdofly

@slotaichi, welcome to the forum! I know you're new here, but if you could either update your signature to include the make, model and year of your t@b, it would help us to diagnose and then offer solutions for the t@b you own. Also we could then ask more appropriate questions. Then finally, what @jgram2 asked, X 2!

Sharon_is_SAM

While it may be true that the headlight trick will provide more voltage, running a 3 way frig on DC will still probably drain your TaB battery.  If you wish to run your 3-way on DC, some folks run the frig off of an inverter, or better yet, pre-cool on shorepower, and use it like a cooler with ice packs during travel.  

Marceline

I've heard of a few instances where the 7pin connector wasn't wired properly and there was no 12v line from the tow vehicle battery to the 7pin connector. 

Cbusguy

as Marceline pointed out we have no idea how his tow vehicle is wired and it is entirely possible that it isn't wired to charge the trailer.    even if it is,   Is the ground wire from trailer to tow vehicle sufficient?    on the tow vehicle side,  what is the condition of the ground?   are both wires of sufficient size to carry 10-30 amps?

Then we run into the issue of tow vehicles alternator,  is it powerful enough to charge two batterys and run the vehicle.  

A lot of questions for sure,   I would start looking at the tow vehicle connector then go from there.   If the battery has been repeatedly ran to below 10 volts it is entirely possible that it is dead and needs replaced as well.   

I agree that 6 hours on a tow vehicle alternator should charge the battery to near full if not completely full capacity.

ScottG

@slotaichi, how are you assessing your battery? Have you measured the voltage before charging, after the drive, and after it dies again?

If your battery is connected and truly depleted, I would expect even the anemic output of your tow vehicle to charge it at least partially. From what you describe, it sounds like you either a) don't have a functioning charge line on your vehicle, so driving around it not actually doing anything, or b) your battery is toast and it will no longer take or hold a charge.