Use a hydrometer to check the state of charge of the battery after doing a "slow charge" of around 10-15 amps at least overnight. The specific gravity of all the cells should be approximately equal and somewhere in the range of 1.265-1.275. A specific gravity reading below 1.250 indicates the need for more recharging, and if any cell shows a specific gravity reading that is 25 points or more below the rest of the cells, replace the battery.

There is no other effective way to tell if the battery is taking a full charge other than monitoring the acid concentration. The charging system voltage with the engine running at a fast idle against a fully charged battery should be around 14.5-14.7 volts with a charging current going into the battery below 15 amps.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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