Using 7-Way Trailer Connector 12-Volt Accessory Circuit to Maintain Trailer Mounted Battery

Updated 08/01/2012 | Published 07/30/2012

Products Featured in This Question

Starter Solenoid - SPST - 12 Volt - 100 Amp - Continuous Duty - Grounded

(14)

$35.71

CTEK MULTI US 7002 12-Volt Universal Battery Charger w/ Pulse Maintenance and Backup Power

(99)

$199.99

Question:

I have an 06 Toyota Highlander Hybrid and an 06 Cruiser RV Funfinder-x trailer. I purchased a Draw-Tite 5100 brake controller and have wired it up per your video. The video shows a +12V contstant power going from the tow vehicle battery to the black wire on the 7 pin connector. When the trailer battery is connected it also shows +12V to the corresponding pin on the 7 pin connector. It appears to me, that the tow vehicle battery and the trailer battery will then be connected in parallel. - Does this mean that when im driving, both batteries will be charged via the cars alternator? If so, will this put too much straiin on the alternator? - When parked, will the trailer be draining both batteries? Should I make sure to disconnect the 7 pin when not driving? - If left alone, will the higher charged battery discharge into the lower charged battery?

asked by: Henry C

Expert Reply:

That is a great question. The 12-volt accessory feed from the 7-way CAN be used to maintain your trailer-mounted battery during travel, but it will NOT recharge a battery from a depleted state. To charge a depleted battery, a charger like the # CTEK56353 CTEK Universal Battery Charger can be used. The 10 or 12 gauge wire used in the accessory circuit will prevent enough current from going through to worry about overtaxing or damaging the alternator.

To prevent the trailer mounted battery from depleting the battery in the tow vehicle, we typically recommend disconnecting the 7-way when the vehicle is parked for more than a short period. If you are concerned about your tow vehicle battery becoming depleted, you should consider installing a battery isolator like part # PK5231201. The isolator will cut power to the accessory feed once ignition of the tow vehicle is shut off.

expert reply by: Mike L