The best and safest way to charge your John Deere mower's battery is with a portable charger. Depending on the voltage of your mower's battery, a jump from a car could seriously damage it. A portable charger can cost upward of $100. It will not only charge your John Deere mower's battery, but your car's as well. Plug it into the wall overnight and you can store it in your trunk for emergencies.
Clean off any corrosion on the cables or terminals. Put on a sturdy pair of work gloves. Then dip a toothbrush into a solution that is equal parts baking soda and water and scrub the area clean.
Loosen and remove the cables connected to your John Deere mower battery's terminals. Remove the negative cable first, followed by the positive.
Attach the portable charger. First make sure that the charger is fully charged, in the "off" position and not plugged into the outlet. Next, connect the portable charger's positive cable clamp to the positive terminal of your car battery. Then connect the negative cable clamp somewhere on the frame of the John Deere mower's frame away from the battery.
Set the charger's voltage switch to 12 volts (For most models. Check your owner's manual to be sure). Then set the amp switch to between 9 and 16, depending on the make and model of your John Deere Mower.
Plug in the portable charger and switch the unit on. Leave it to charge until the indicator light on the charger indicates that the mower's battery is fully charged.
Unplug the portable charger. Then set the power switch to the "off" position. Next, remove the negative cable from the frame of the John Deere mower. Then, remove the positive cable from the battery's positive terminal.