There are primary carbon battery, alkaline battery and secondary Ni-Cd/Ni-MH battery. Thus, AA battery voltage should respectively involve primary AA battery, AA Ni-CD battery and AA Ni-MH battery.
1. Rated voltage of primary AA battery is 1.5V and cutoff voltage 0.9V. This is the common point for alkaline and carbon zinc battery. Discharge time to 0.9V is criterion of how to judge primary battery capacity, which is the most vital performance parameter.
2. Ni-Cd battery: rated voltage is 1.2V. Discharge cutoff voltage is related to discharge rate. Cutoff voltage of 8-hour discharge rate is 1.1V while that of 5-hour discharge rate is 1.00V.
3. Ni-MH battery: discharge cutoff voltage is 1.0V, charge cutoff voltage 1.5V and rated voltage 1.2V. AA lithium battery often mentioned is actually 14500 battery, whose rated voltage is 3.7V.
Charge and discharge curve can help understand phase characteristics of AA battery voltage.
1. Comparison of AA carbon and alkaline battery discharge curve reveals slower voltage drop of alkaline battery under 3.9Ω discharge, which is the fundamental reason for its more durable performance.
2. Ni-CD and Ni-MH charge& discharge performance finds that battery discharge voltage of Ni-CD battery falls faster than that of Ni-MH battery when charge terminates.
AA battery voltage is marked on battery case. Over charge or discharge to rechargeable battery will damage electrodes and cause irreversible reaction unable to restore. For primary battery, over discharge to AA battery will lead to battery leak.