The only really effective way to check the battery is to monitor the voltage at the posts (not the cable connectors) while the engine is cranking. A good 6 volt should show a minimum of 4.5-5 volts with the starter running under load, and the voltage should stay there for 20-30 seconds of continuous cranking. Spin the engine with the ignition disabled to use the starter as a battery load device. Even an almost dead, or defective battery will show 6 volts without a load on it.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!