What Is a Battery?
A battery is a portable power source that converts the energy produced by a chemical reaction inside it into electrical energy. It enables operation independent of the mains.
Primary and Secondary
Primary batteries are single-use; they deplete and are thrown away (like alkaline). Secondary batteries are rechargeable and used again and again (like Li-Ion, NiMH).
| Parameter | Meaning |
|---|---|
| Voltage (V) | Depends on the cell chemistry |
| Capacity (mAh) | The amount of charge stored |
| C-rate | Safe charge/discharge rate |
Capacity (mAh)
Capacity shows how much charge the battery stores. A 2000 mAh battery can give roughly 2000 mA for one hour (or 200 mA for ten hours). Together with the current the device draws, it sets the runtime.
C-Rate
The C-rate expresses how fast the battery can be charged/discharged relative to its capacity. A high C-rate means being able to give high current; exceeding the limit causes heating and damage.
Where Is It Used?
Remote controls, phones, laptops, toys, uninterruptible power and all portable devices.
Series and Parallel Connection
When cells are connected in series their voltages add (e.g. 3.7V + 3.7V = 7.4V); connected in parallel the capacity (mAh) adds and the voltage stays the same. Depending on the device's need, cells are combined these two ways to get the desired voltage and runtime. To connect cells to a board or device, a battery holder is used.
Common Mistakes
- Charging a primary: charging a single-use battery is dangerous.
- Mixing series/parallel: mixing cells of different age/capacity creates imbalance.
- Over-discharge: fully draining a rechargeable battery shortens its life.
Frequently Asked Questions
What does mAh mean?+
Can every battery be charged?+
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