Find a position for the battery then connect them together in parallel that is negative to negative positive to positive. That way you will still have 12 volts with larger capacity. Don't connect them in series that is positive to negative because you will end up with 24 Volts.
Edison was said to have noted this emission when a wire paralleling a light bulb filament showed current flow if the filament was more negaive than the wire, but not if the filament was more positive than the wire. Note that the wire is not touching the filament. The wire was inside the bulb with the filament. First Edison lit the bulb with a simple battery circuit. Then the wire was connected to a current meter and other terminal of the current meter to a second battery and the other end of the second battery to either end of the first battery. Depending on which way the second battery is set, the ammeter indicates an electric current flowing through the wire or not.
You can wire two 12 volt batteries in series... Connect negative of the first battery to positive of the second battery. That common connection becomes ground. The positive of the first battery becomes +12, and the negative of the second battery becomes -12. However, do not expect to be able to charge the second battery in a system designed for only one battery, such as in an automobile.
Dead battery or a broken battery wire
dead battery or a broken wire between the battery and the starter
the fastest way is to disconnect the battery ground wire at the battery for about 10 seconds
A bad ground wire or main fuse is blown.
For the coil which is closest the the radiator: first wire goes in the cylinder one (first one from the passenger's fender). Second wire in the coil goes in the cylinder #3. For the second coil which is closest the firewall, first wire starting from radiator goes in the cylinder #2 and second wire in the #4.
A Wire can be part of a battery substitute device such as that found at batsub.com.
Remove the starter power wire from the battery that goes to starter. Starter is between the transmission and engine. Remove the 3 bolts from the starter to the transhousing. Replace new starter re-install the power wire.:) Disconnect the battery first!!! Also, besides the battery cable there should also be a starter switch wire (probably a spade connection).
A tiny 2-prong junction box on the firewall. one wire comes to it from the Ignition, & the other wire goes out from it to the starter. If you take a jumper wire from the positive on the battery & touch it to the post on the junction box where the starter wire comes out, with the key on, It should start the truck. If it doesn't, you need a new starter.
The red battery wire goes on the positive + battery terminal no matter which side it is on. The black wire goes on the negative - terminal.
A location to secure it, and proper wiring. You will need to wire it parallel, not serial.