NEWS | March 16, 2021

Tactical Wheeled-Vehicles: Safe Slave Starting

Photo by Sgt. Wayne Becton
This article initially appeared in PS 720 (Nov 12), p. 11-12.

Combining weak batteries with freezing temperatures won’t exactly give your vehicle the best environment for starting. But with the right help, you can get it cranking.

The right kind of help is using slave cables correctly. That will keep you safe and your vehicle on the job. Here’s how:
  • Read the slave-starting steps in your vehicle’s operating instructions.
  • Never stand between vehicles being slaved and never position them nose-to-nose. That’ll keep you and your vehicle safe in case one vehicle moves when it starts.
  • Have your mechanic make sure the electrolyte in all battery cells is above the plates and is not frozen. Never slave frozen batteries. They can explode.
  • Make sure all cables and terminals on the dead vehicle’s batteries are tight and free of corrosion.
  • Set the parking brakes on both vehicles. Shift both transmissions to neutral. Keep the live vehicle’s engine running at fast idle (1,000-1,200 RPM).
  • Make sure the dead vehicle’s battery switch is OFF to prevent arcing when you connect the slave cable.
Once you’ve done all of the above steps, follow these next steps and make sure to do them in order!
  1. Connect the slave cable to the dead vehicle’s slave receptacle. The connection should be tight.
  2. If either vehicle has the old two-prong slave receptacle, use the NATO adapter, NSN 5935-00-322-8959. Put the adapter on the receptacle and then connect the cable.
  3. Push the slave cable connector into the slave receptacle on the live vehicle.
  4. Wait at least one (1) minute, but no more than three (3), before trying to start the dead vehicle. This allows a trickle charge to warm up dead batteries before they get the full jolt.
  5. If the vehicle has a clutch, step on it to reduce engine drag. Try to start the dead vehicle.
  6. Keep the slave cable connected until the vehicle starts. Never unhook a slave cable while the starter is engaged, or you’ll get arcing and burned-out cables and receptacles.
Once the slaved vehicle has started, pull off that vehicle’s cable and then remove it from the other one.

Let the engine run in the slaved vehicle at fast idle (1,000-1,200 RPM) for at least twenty (20) minutes or drive the vehicle about five (5) minutes to recharge the batteries.

Tell your mechanic if the batteries don’t recharge.