Corrosion or a very loose connection at the positive terminal.
Look for a loose or corroded positive battery cable at the battery post - or a loose/corroded battery terminal on the positive cable.
You've probably blown a relay. When you reconnect a battery, you connect the positive terminal first.
Current flows from negative to positive. The current flows because of OHM's law. Click the link.
You just connect them in Parallel. Two 12 volt batteries connected in parallel will output 12 volts. Two connected in Series will output 24 volts. Just connect the negative terminal on the first battery to the negative on the second battery. Then connect the positive terminal on first battery to the positive on the second battery. Connect the cables to the second battery, positive to positive and negative to negative. Click the link for a diagram.
It is too complicated to explain here. Click the link.
Typically, a Click-click-click noise when attempting to start a vehicle is the sure sign of either a dead battery or a loose battery connection. Try tightening the battery terminal connections. If this doesn't help, you may need a new battery. A jump start will avoid a towing expense.
Low battery voltage. Either battery cable may be loose at the battery or at the positive terminal of the starter solenoid. The solenoid contacts are not making when it pulls in. The brushes are worn out in the starter motor. Whack the starter with a hammer while someone tries to start. sometimes that will jar it into working.r
It could be a loose battery terminal or dead battery! A faulty starter solenoid/relay will often only click once when tryong to start the vehicle.
That's usually a low battery or a dirty battery terminal. Check the terminal first, see if it's corroded or loose. Next, understand that the battery is simply an electrical storage device. The battery can be bad or the alternator can fail and the battery will not have enough stored electrical energy. Before just replacing a battery, always check the charging system to make sure it's working properly before assuming that a battery has failed.
First off you must have the same type batteries. Connect the positive post of the first battery to the positive post of the second battery. Then connect the negative post of the first battery to the negative post of the second battery. Now connect the positive post of the first battery to the positive connection on the vehicle. Then connect the negative post of the first battery to the negative cable of the vehicle. Click the link for a diagram.
To reset the computer in a car disconnect the negative battery terminal until you her a click ( it will be about 5 mins), then it is done.
This could be the voltage regulator. Both the positive from the battery and the starter would be connected to it.