disconnecting battery while engine is running

[iward]

Will any damage be done if a battery is disconnected while the engine is running?

Thank you.

[Davescort97]

Yes, with the ignition on and high idle you can blow relays, radio and other electrical equipment. You need the battery to absorb amperage and voltage spikes. Some say this is a test to see if the alternator is charging. Instead, measure voltage at the battery while the engine is running. Should be about 13.8 volts. Don't test your alternator by disconnecting the battery.

[chrisanthony]

yea not a good idea..turn the car off first..then disconnect the negitive first then the positive