Analysis of nickel metal hydride battery voltage

The 1.2V nickel-metal hydride battery used daily, its full-voltage is usually 1.4V, and the discharge termination voltage is 0.9V.

This means that the Ni-MH battery is inconvenient to use when it is discharged to 0.9V and should be charged. Therefore, 0.9V is both the termination voltage at the time of discharge and the starting voltage for charging the Ni-MH battery. In practice, since nickel-hydrogen batteries after 0.9V still have some small currents, it is also feasible that some nickel-hydrogen batteries have a starting voltage of 0.8V.

The voltage after the Ni-MH battery is fully charged is about 1.4V, which can be regarded as the highest voltage, but the individual battery depends on the specific charging method.

One case is to charge with constant voltage. The older charging method is still set up like this, generally set to 1.4V, but the consequence may be that the battery may not be fully charged when it reaches 1.4V. In this case, the nickel hydrogen battery charging termination voltage is not the nickel-hydrogen battery saturation voltage.

The above defects are mainly caused by the charging current, and the large current charging may not be fully charged at 1.4V. From the charging curve point of view, some 1C-charged Ni-MH battery capacity reaches 100% of the voltage can reach the target of 1.53V, and then, at this voltage, the head is turned back down to 1.4V, so 1.53V becomes With the highest charging voltage, Ni-MH battery chargers often pass this feature to set the inflection point voltage to the charging cut-off time.

The comparison of the charging current with the large current and the small current charging is: the small current can be fully charged at a lower voltage value, and the charging can still be slowly increased after the full power is charged. On the contrary, the large current above 1C is at the full power state. Continue charging, the voltage does not rise and fall. Therefore, after the voltage reaches a certain height (such as 1.36V), it is more reasonable to charge with a small current of about 0.3C.

The constant current charging method uses the temperature rise rate method as the basis for judging the end of charging. For example, under the charging condition of 0.3 C, the temperature rises by 2 ° C per minute, and the charging is stopped. At this time, the nickel-hydrogen charging voltage is generally around 1.4 V.

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