How can i tell if a 12V battery is dead?

Before you can test it it will have to be charged. So take it out and charge it full on trickle charge for 2 or 3 hours and then use a volt meter and check the voltage. It should be at least 12 volts or higher.

It may have to be put under a load test as well for a short time to see if it holds its power. So if it is good on the voltage then try to put it on some thing that is 12 volts a light for a few minutes and check it that way you can see if it is holding the charge.

Merry Christmas

1

Putting a meter on a battery under no load wont tell you squat! You can test the battery and the meter might say 12v and you could think that is fine, but once under heavy load that voltage would drop making the battery useless for the application.

Using a instrument like this will tell you how charged your battery is>> http://i.ehow.com/images/GlobalPhoto/Articles/5221...

Charge the battery for a few hours and come back to what you're doing.

Borrow a multimeter and test the battery for 12 volts DC.

lick finger, touch one end of battery with finger and touch other end with tongue. if you get a slight tingle in your tongue, its fine. you could also wire up a 12v load, like a car charger or any vehicle accessory to it. otherwise, get a cheap meter. 3 options that work.