I have craftsmen 19.2 volt tools while using the electric sander my batteries have died and when i put them in the charger the green indicator light comes on saying they are fully charged , when in reality the batteries are dead. I just bought these batteries one week ago so it should not be a battery problem. What is going on?

That particular battery is defective and falsely indicating it is charged.

check the charger with a multimeter and make sure that it is putting out at least 13.8-14.6 volts

It could be a defective battery or it might just be normal for the charger and it lets you know its charging. Look in the manual for the tool and it should tell you why it blinks and turns off. If you dont have the manual i'm sure you can look it up online.

Directions say green light indicates that the battery is fast charging only,it does not indicate at exact point of full charge. I let my batteries charge for 12 hours for the first time charging,found out myself the same way. Try that and you will notice the difference.

Did u ever figure out what the salution was

You can determine exactly what is going on by using a small handheld voltmeter. They are inexpensive, easy to use and come in very handy. Just test the output of the charger (after noting what the volt-output-rating is) by touching the leads of the meter to the terminals on the charger. If the charger is working at all, this is not a dangerous test. Conversely, test the output of your batteries by touching the leads of the voltmeter to the terminals on them. I suspect the charger is bad because after they overheat, they quit working and some don't last very long. I don't think YOU are doing anything wrong, just maybe the companies that manufacture these 2 electrical products are.

check your battery and charger with a multimeter and make sure that they show at least 12 volts

change batteries, your charger should indicate wheather you battery is good or noot on the pause inbetween blinks.

The green light means it is ready to use. If the battery is bad though, the light will still be green. 

This is likely a code from the computer system on the CMM1200 that the batteries no longer hold a charge. If you have a voltmeter, a "quick test" is to put the batteries on the charger for at least 8 hours and then test the DC voltage of the batteries. Test each battery separately by taking the cables off and testing the battery at the positive and negative lead. If they read less than 11.5 volts, you need a new battery set. You can get replacements from www.batteryinternational.com/universal-battery-ub12180-batteries-by-brand-universal-battery-nb.html. The model you have requires two of these batteries. Hope this helps.