Is a Battery Isolator Needed for 7-Way Wiring on 2001 Ford F250

Question:

As i understand it, connecting different capacity or different types of 12v batteries in parallel is frowned upon due to under charging and over charging. The batteries on use on my 01 f250 are VERY different than the small battery used on my trailer winch and break-away. Does this require the use of a diode based isolator instead of a simple relay, or do most trucks used for towing have a isolator already installed on the 7 pin charging wire?

asked by: Will A

Expert Reply:

The 12-volt power source at the 7-way connector is typically protected by a 40 amp fuse or breaker. This circuit is usually tied directly to the battery, with the fuse or breaker installed inline. This circuit is not isolated. Because this circuit can remain live even when the ignition is switched off (depending on the vehicle), we recommend unplugging the trailer when the vehicle is not running to avoid the battery from being discharged. If you wish to avoid this problem altogether, using an isolator like part # PK5231201 will cut off power to the 12-volt feed when the vehicle is switched off.

The 12-volt feed will be able to maintain your batteries, but due to the limited amperage capacity on the circuit, it cannot be used to charge a dead battery. When short power is available, you can use a battery charger like # CTEK56353.

You do not mention which break away system you have, many breakaway batteries have their own charger built in that will prevent the small battery from being overcharged. If your system does not already have a charger, we offer part # 20011.

expert reply by: Mike L