Batteries are essential in our everyday life.
They provide power to a plethora of portable devices like TV remotes, smartphones, wireless keyboards, smartwatches, clocks, and so much more.
While having one universal battery available for all applications might save a lot of hassle in choosing the right one, the world of batteries is filled with many different types.
Batteries can differ in certain characteristics which include; chemical composition, voltage, physical dimension, specific energy, specific power, performance and lifespan.
Due to this, one type of battery might be more suitable for a particular application compared to another.
Can you replace NiMH batteries with Lithium?
Yes, you can replace a NiMH battery with a lithium battery. To replace NiMH batteries with lithium, you will need to ensure they are the same size, shape and voltage rating. However, practically it is not a good idea as each battery is designed for different applications. A NiMH battery is more suited for applications requiring high current draw (like power tools) compared to Lithium batteries.
This article will take a closer look at each battery, as well the key characteristics of batteries and why replacing a NiMH and Lithium battery isn’t really ideal.
Key characteristics of rechargeable batteries
While some characteristics of a battery might be distinguishable by just looking at them (things like their shape and size), there are other key characteristics which you won’t be able to find out by looks alone.
These characteristics ultimately determine what type of applications the battery will be used in, as every application has different needs and demands.
The key characteristics of batteries include;
- Nominal Voltage
- Specific Energy
- Specific Power
- Performance
- Lifespan
Nominal Voltage
Is the normal voltage that the battery provides. Some batteries might indicate a higher voltage at full charge, however, this voltage drops down to its nominal voltage soon after.
Specific energy
This is basically the current capacity of a battery which relates to how much current a battery is capable of storing for its given weight.
If a device needs to operate for long periods of time at a moderate load, batteries with higher specific energy are the ideal choice.
Specific Power
Is the battery’s ability to provide high current. The higher the specific power, the larger the current it can output.
If a device needs a high current for a short amount of time, batteries with higher specific power are the ideal choice. The tradeoff is that the specific energy of the battery decreases.
Performance
A battery is going to be subject to a wide range of temperatures. The performance of a battery gives an indication of how well it will perform to these different temperatures.
Extreme heat can reduce the lifespan of a battery, while extreme cold can temporarily lower its performance.
Lifespan
This tells us how long a battery is going to last. Things like temperature, depth of charge and load play huge roles in determining the lifespan.
As we saw above, heat can drastically reduce the lifespan of a battery.
Deeper look at NiMH and Lithium batteries
To better understand the question at hand, it will help to learn a bit about both batteries.
NiMH batteries
Let’s start with NiMH batteries.
The battery is available as disposable (can only be used once), or as a rechargeable (which means they can be used multiple times as long as it is recharged ).
Most of the time (if not all), batteries get their name from what chemical they are composed of. In this instance the chemical composition is Nickel Metal Hydride (where NiMH is just an abbreviation).
Different types of NiMH Batteries
NiMH batteries are available in various different sizes for different types of devices. While their size varies, the majority of them provide a nominal voltage of 1.2 volts.
However the size of the battery will affect its current capacity. The smaller the battery, the lower the current capacity, and vice versa.
Below is a list of the different sizes of NiMH batteries (which are split into two categories; consumer and industrial). They are available with or without tabs.
Consumer;
- AA
- AAA
- C
- D
- 9 volt (rectangular)
Industrial;
- Sub C
- A
- 1/3 AA
- 1/3 AAA
- 2/3 A
- 2/3 AA
- 2/3 AAA
- 4/3 A
- 4/5 A
- 1/2 D
Electronic devices that use NiMH batteries
Due to their ability to deliver high current (specific power), NiMH batteries are used in high drain electronic devices that require this large current to operate.
A digital camera is an example of a device that requires a high current around 1000mA (mainly for the flash). NiMH batteries are able to deliver this current without losing too much of its capacity.
Other electronic devices that use NiMH batteries include;
- Flashlights
- Portable Vacuum Cleaner
- Portable power tools (drills, jigsaws, circular saws, sanders, grinders, etc)
- Electric toothbrushes
- Electric razors
- Camcorders
Lithium batteries
Next up are Lithium batteries.
The most common of lithium batteries used in portable electronic devices is the Lithium Ion. So, going forward this type of Lithium battery will be used.
Just like the NiMH battery, the lithium ion battery is aptly named due to it using lithium ions.
During the discharge cycle, the lithium ions move from the negative terminal (cathode), through an electrolyte to the positive terminal (anode).
Different types of Lithium Ion Batteries
Lithium Ion batteries come in a variety of shapes for different applications.
- Small cylindrical (single cell with, solid body, with no terminals)
- Large cylindrical (single cell,solid body, with threaded terminals)
- Flat or pouch (soft, flat body)
- Rigid plastic case (large threaded terminals)
- AA
- AAA
- 9V (rectangular)
Electronic devices that use Lithium batteries
Lithium batteries have a much lower specific power rating compared to NiMH batteries. But, this reduction in specific power results in higher specific energy which means they can provide current for longer periods of time.
This is ideal for devices that do not require high currents, but need to operate for longer periods of time.
Devices such as;
- Smartphones
- Smartwatches
- Wireless keyboard/mouse
- Wireless speakers
- Wireless earphone/headphones
- Vaping devices
- Electronic toys
Can you replace NiMH batteries with Lithium?
Now that we have learnt about some of the crucial characteristics, as well as a little about each battery, we can delve into whether we can replace a NiMH with a Lithium battery.
All batteries have the same task, which is providing power to electrical and electronic devices. But, as we saw there a set of characteristics that ultimately determine the ideal application where a battery will be used.
NiMH have higher specific power, making them ideal for applications that require a large hit of current for short periods of time.
Lithium batteries on the other hand have higher specific energy, which is perfect for devices that require less current, but need to last for longer.
At the beginning of the article we saw that you might be able to replace a NiMH with a Lithium battery, however this is not the best idea.
But why?
This comes down to the specific power and energy of each battery.
Say you have a portable vacuum cleaner. The vacuum cleaner requires a high current to run the motor to suck dirt on the ground.
A NiMH battery is best suited for a vacuum cleaner as it can provide this high current.
Now, if we replace this NiMH battery with a Lithium counterpart, the lithium battery is not going to be able to provide the sufficient current to run the motor of the vacuum cleaner.
But, there are many high current devices that use Lithium batteries. How is this possible?
These batteries are designed specifically for certain applications and are not your typical consumer batteries that can be bought off the shelf at your local electronic store.
They are designed to have high specific energy and power.
For example, electric cars require high current for the motors, and need to last a long time as well (otherwise you won’t be able to get very far).
What’s the best option if you need to replace the NiMH batteries?
If you need to replace a NiMH battery, your best option is replacing it with another NiMH battery of the same specification (voltage and current capacity).
This way the performance of the device it is being used in will not be affected.
