Low-voltage nickel-metal hydride batteries have no memory effect. High-voltage nickel-metal hydride batteries have the same "memory effect" as nickel-cadmium batteries. Lithium-ion batteries do not have a memory effect. The memory effect is an effect of the battery causing crystallization of the battery contents due to use. Generally only occurs in nickel-cadmium batteries, nickel-hydrogen batteries are less, lithium batteries do not have this phenomenon. The reason for this is due to incomplete partial charging and discharging of the battery. This will reduce the temporary capacity of the battery, resulting in the shorter use times.
To prevent the memory effect of the nickel-cadmium battery, the battery should be used until the battery is discharged, or the battery can be discharged first. Never recharge a battery that has electricity to avoid memory effects. To completely discharge the battery, the battery must be placed in standby for about 24 hours. After it is fully discharged, it can be fully charged. If it is cycled many times, the battery capacity can be restored unless the battery is damaged. However, to avoid this phenomenon, it is recommended that consumers choose nickel-metal hydride batteries or lithium batteries.
Like lithium batteries, nickel-metal hydride batteries also require a battery management system, but they pay more attention to the battery charge and discharge management. The reason for this difference is that the nickel-hydrogen battery has a "memory effect", that is, the capacity of the battery will be attenuated during the cycle of charging and discharging, and overcharging or discharging may aggravate the capacity loss of the battery. Therefore, for the manufacturer, the NiMH battery control system will actively avoid excessive charging and discharging in the setting, such as artificially controlling the charge and discharge interval of the battery within a certain percentage of the total capacity to reduce the capacity decay speed.