No More Dead Toad Battery - PriorityStart!

Recently, I switched from dolly towing to flat towing out Honda Fit. Flat towing is more convenient and I don’t have to figure out where to store the dolly at the campsite (often times it can not be kept on site).

Most cars with automatic transmissions cannot be flat towed (all 4 wheels down). Our 2010 Honda Fit is one of those few automatic transmission cars that can be towed. However, in order to leave the car in neutral, the key has to be in the “Accessory” position. This has resulted in a dead battery if we tow for more than a few days without disconnecting and driving the vehicle.

There are several solutions I considered.

  • Remove the fuse or fuses that power the radio and dashboard.
  • Install a battery disconnect switch.
  • Add a “Battery Saver” device.

Removing fuses on the Honda Fit is a chore. The fuse panel is located to the left and below the steering wheel. I can’t access it without getting out of the car and kneeling on the ground. There is a space on the dash to add toggle switches and I’m considering adding a switch to shut off the battery draining circuits.

Installing a battery disconnect switch is inexpensive (~$10) and easy. The downside is I have to pop the hood and remove the key/knob on the switch.

The “Battery Saver” option is the most expensive (~$100) but is completely automatic after installation. I opted to use a product called PriorityStart! 12v ProMax.


It disconnects the battery if it drops below 11.8 volts. To re-engage, just tap the brake pedal. 11.8 volts is plenty of reserve to start the car.

PriorityStart! is a sophisticated device that is smart enough to know not to disconnect the car when it is running. The FAQ describes the incorporated safeguards to prevent false activation.

For many cars installation is straightforward and does not involve cutting wires or other complicated procedures. No permanent modifications are required.

Our Honda Fit has a busbar incorporated into the positive battery lead and prevented me from attaching the positive battery lead directly to the device as is normal. As you can tell from the pictures below, I added a 12-inch cable. This allowed me to attach to the battery lead without modifying the busbar and position the PriorityStart! in a more accessible location. I used electrical tape to insulted the exposed ring terminal.



Despite the small size of the engine compartment, I was able to fit a supplemental braking system (Air Force One) and the PriorityStart! under the hood.

I’ll report back in a future post about the performance of the PriorityStart!

Written on October 3, 2018