Depending on the age of the vehicle you probably have shorted or grounded the electrical system causing fuse(s) to blow. Question was kind of broad may want to be more specific
once a battery is connected even if the key is not in the ignition, there is always power at certain points in your car. Connecting a battery backwards will not start your car, but it can and will fry the wires to your starter.
it will arch out and melt the knobs on your battery and your cables
Nothing as long as you did not then connect the other cable.
You should connect the negative cable to the negative. Your question sort of stopped. Connect to a negative what?
When you connect the battery backwards you can cause major damage. You can blow the alternator or its fusible link. You can destroy electronics, particularly the various computers - and these are not cheap.
Very Dangerous........it would be a dead short. andcouldcause a fire or explosion.
Voltmeter will give you opposite readings or will not work at all.
You cannot charge it connected backwards. You will destroy the battery.
Dead battery -will no longer charge.
What happens when you inadvertently crossed the positive battery terminal from a negative to a positive and a positive to a negative.?Read more: What_happens_when_you_inadvertanly_crossed_the_positive_battery_terminal_from_a_negative_to_a_positive_and_a_positive_to_a_negative.
Voltage Options using Two 12 Volt BatteriesEach 12 volt battery HAS 12 volts in a stand-alone configuration.If you want to "get" 12 volts and yet use both 12 volt batteries, then you hook them up in a "parallel" fashion.Parallel connection means that a cable is used to connect the positive [+] terminal of one battery to the positive terminal of a second battery. And another cable is used to connect the negative [-] terminal of first battery to the negative terminal of the second battery. This configuration provides the same 12 volts, but allows greater current [Amps] to be available.Another configuration ["series" connection] will create a 24 volt battery from the two 12 volt batteries.Series connection involves the use of only one cable to connect the positive terminal of one battery to the negative terminal of the second battery.NOTE: it is CRITICAL that you NEVER connect a cable or wire between the positive and negative terminals of the same battery, or series of batteries. IF this happens, a condition called a 'short circuit" occurs, and WILL result in gigantic sparks [arcing], much heat, and the very distinct possibility that the the battery will explode in your face!!!!!
When replacing the battery on my son's Kawasaki Vulcan 500, I accidentally hooked up the battery backwards. I had purchased an EverStart battery from Wal-Mart and the orientation of the main battery terminals was backwards from the original battery. Anyway, it blew the main fuse located in the left hand side side cover.