NiMH vs. Li-ion: A Battery Comparison
A Comparison Between Nickel-Metal Hydride (NiMH) and Lithium-ion (Li-ion) Batteries
Modern society is powered by various electronic devices such as cell phones, laptops, and cameras. All of these things use batteries. There are many types out there and each type has their strengths and weaknesses. For this article, we will discuss and compare NiMH and Li-ion batteries.
These types of batteries are usually used for high drain devices like laptops, cellphones, iPods, and digital cameras. However, they have some distinguishing features which make one type more efficient in than the other in some regards.
- High Energy Density: These have an average of 2200mAh (milliampere hours—the amount of current in milliamperes that it can give multiplied by the time in hours.) This is greater than the 1500mAh seen in Li-ion batteries. These are the standard numbers in 1.2v NiMHs and 3.7v Li-ions.
- Compatibility: If you have ten gadgets using an NiMH battery, you can use a single pack to power them all. Not simultaneously of course. NiMH uses standard sizes so they are compatible with all devices using sizes such as AAA or AA. Compared to Li-ions, the sizes depend on the manufacturer or model of the device. I did see some AA size Li-ions around the market so it may be worth checking them out.
- They Are Safer: They have less active materials compared to Li-ion batteries. NiMH can pop if they are overcharged too much or short circuit but this is nothing compared to a Li-ion which can potentially blow up.
- Can Be Completely Discharged: By this I mean they can be brought down to 0 charge, if you can get it to reach that. They will still charge, just don't let it suffer from reverse polarity or else they will be damaged.
- High Self Discharge Rate: NiMH lose a large percentage of their charge every month. The number is around 5% on the first week after the charge and about 50% on the first month. There are low-self discharge (LSD) rate types available. They are more reliable than the standard NiMH but they have lower capacities, usually around 2000mAh.
- Unreliable for Low Load Devices: You should not use NiMH batteries for devices such as clocks. They will lose charge faster through self-discharge rather than the load. Use alkaline, Li-ion, or lithium batteries instead.
- Low Voltage Output: Each AA cell can only give 1.2v compared to Li-ion cells which can give 3.7v.
- Long Charging Time: The standard charge time of a NiMH is 10-12 hours. Fast charging these cells can result in damage. Li-ion cells can be charged at around 1-3 hours depending on capacity.
- Cannot Operate at Extreme Temperature: At extreme temperatures, NiMH voltage output will drop. Li-ion batteries can tolerate these temperatures to some extent.
- Reliable: These have a significantly lower self-discharge rate than a NiMH battery. As a result, they can be used for low-current devices like clocks or watches watches.
- Small: They are smaller and lighter compared to NiMH batteries.
- Higher Voltage Output: A single cell can deliver 3.7v while even two NiMH cells can only give 2.4v.
- Faster Recharge: Li-ions can be charged in about 1-3 hours, depending on capacity. This is much faster than the 10-12 hours needed for NiMH batteries.
- Temperature Tolerance: These can better stand low temperature and warmer environments compared to NiMH cells.
- Higher Energy Density: This means that the battery carries more charge per gram than a NiMH battery.
- Lower Capacity: These have an average of 1500mAh compared to the 2200 mAH average of NiMH cells.
- Incompatibility: Different manufacturers make different sizes and shapes for Li-ion batteries, making them usable only to a specific set of devices. NiMHs have standard sizes.
- Have Active Materials Like Lithium Batteries: Ions are a very active material. They can react easily and generate a lot of heat. That’s why there are circuits in those cells. They are used to check for voltage and temperature. In other words, the circuits prevents the cells from blowing up.
- Cannot Be Completely Discharged: If a Li-ion battery gets fully discharged, it will be damaged. Yes, you can shock charge it but its efficiency will decrease. Always keep this kind of battery charged above 50%.