The two terminals in a battery are called the negative and the positive terminal.
The negative is the ground while the positive is the power output side.
The negative is a - and the positive battery terminal is marked as the +
Most battery cases are marked positive (+) on one end and negative (–) on the other.
These markings indicate the positive and negative battery terminals.
The direction of the electric current in a closed circuit is from the negative (–) terminal of the battery to the positive (+) terminal of the battery.
Battery terminal bolts for side post batteries are 10 mm head size although some may be 5/16"
Some battery terminal bolts are 3/8-16 with a 5/16 head.
You can buy a battery terminal bolt wrench that will fit the battery terminal bolts.
To remove a stripped out battery terminal bolt try using a pair of vice grips on the bolts head.
The vice grips should hold onto the battery terminal bolt that is stripped and then you should be able to remove the bolt.
Or you can also use a small pipe wrench that should help grasp the stripped out head of the battery terminal bolt and it should come out that away as well.
If you still can't get the battery terminal bolt out and the battery is bad then you can just cut the battery cable ends off and replace them with new battery cable ends.
Then install new battery terminal bolts.
But if it's just the head of the battery terminal bolt that is stripped out then using a pair of vice grips, locking pliers or a small pipe wrench should get the stripped battery terminal bolt out.
Then replace the battery terminal bolts with new ones.
Also remove the negative battery terminal bolt first to avoid sparking the battery terminals with the ground.