how do you check for a shorted cell in the battery??

OK still have the battery light comin on in my car I have had the alternator out several times had it rebuilt and tested and have also put in a new regulator and fan belt and the lights still stayin on. I have read here it could be a shorted cell in the battery how would I check for that. My last ditch effort before I have to take my car to my wrench any imput would be appreciated.

from porsche tech bulletin: if light does not go out, exciter current is too weak because of 2W lamp. in this case, resister 911 641 981 00/91 ohms, 5W, must be installed parallel to battery charge indicator lamp. ( between the 2 terminals on the lamp socket). 82 on should have a 4W bulb. is there a ground strap from the alternator housing to the engine case? usually a load test will show whether a battery is good, along with a hydrometer reading. on a fully charged battery, 15 seconds @ 150A load, the battery should not go below 10.5V. the hydrometer will show any dead cells.

[This message has been edited by john walker's workshop (edited 04-27-2001).]

Umm...wouldn't it be easier to take the battery down to the local Wal-mart (or wherever) and have them load-test it?