(1) Weight
In terms of the voltage of each individual cell, nickel-metal hydride (NiMH) and nickel-cadmium (NiCd) batteries are both 1.2V, while lithium-ion batteries are 3.6V, making the lithium-ion battery voltage three times that of NiMH and NiCd batteries. Furthermore, lithium-ion and NiCd batteries of the same type have almost the same weight, while NiMH batteries are heavier. However, because lithium-ion batteries have a terminal voltage of 3.6V, the number of individual lithium-ion cells can be reduced by two-thirds to achieve the same output voltage, thus reducing the weight and volume of the final battery pack.
(2) Memory effect
Nickel-cadmium (NiCd) batteries have a memory effect, therefore periodic discharge management is necessary. This periodic discharge management is a passive management approach in a vague state, even discharging the NiCd battery when its charge level is uncertain (the frequency of discharge or the discharge after several uses varies depending on the NiCd battery manufacturer and usage). This cumbersome discharge management is unavoidable when using NiCd batteries. In contrast, lithium-ion batteries have no memory effect, making them very convenient and simple to use. There is no need to consider the residual voltage of the secondary battery; they can be charged directly, naturally shortening charging time.
The memory effect is a major enemy of rechargeable batteries, generally believed to be caused by long-term improper charging, which can lead to premature battery aging. The memory effect prevents batteries from charging effectively, resulting in them charging to full capacity only to discharge completely. To prevent the memory effect, strictly adhere to the principle of full discharge before charging, meaning that it's best to completely discharge the battery before charging and then fully charge it in one go. Nickel-cadmium (NiCd) batteries are particularly prone to the memory effect, so special care should be taken when charging them. Nickel-metal hydride (NiMH) batteries theoretically do not have a memory effect, but it's still best to follow the principle of full discharge during use; this is why many chargers offer an additional discharge function. For batteries whose capacity has decreased due to the memory effect, repeating the process of fully charging and then fully discharging several times can often repair most batteries.
(3) Self-discharge rate
Nickel-cadmium batteries have a self-discharge rate of 15%–30% per month, nickel-metal hydride batteries 25%–35% per month, and lithium-ion batteries 2%–5% per month. Among these three types of batteries, nickel-metal hydride batteries have the highest self-discharge rate, while lithium-ion batteries have the lowest.
(4) Charging method
The charging of rechargeable batteries has always been a focus of attention, as correct and proper charging methods can ensure battery life. There are various recommended charging methods for rechargeable batteries, and different methods place different requirements on the charger's circuitry, naturally affecting the charger's production cost. The relationship between battery charging time and charging current is as follows: dividing the battery capacity by the charging current yields the charging time. Considering losses during the charging process, the resulting charging time is then multiplied by a coefficient of 1.2.
