The short answer is Yes. Power supplies are used to convert the alternating current (AC) or direct current (DC) from a power source, such as mains electricity or a battery, into the AC or DC an electronic device needs to function. Battery chargers can also do this but primarily supply a constant voltage or constant/limited current to rechargeable batteries to replenish their state-of-charge.
Most power supplies and battery chargers cannot be used interchangeably because power supplies do not have the ability to terminate charging once complete.
What are power supplies?
The main feature of a power supply (also known as an electric power converter) is that it converts AC or DC from a power source to the correct AC or DC, voltage, and frequency to power an electronic device. Power supplies can contain additional safety features to, for instance, limit the current requested by the device to a safe level, shut off the current in the event of a malfunction, and prevent electronic noise or voltage surges from impacting the device.
Most commonly, power supplies are connected to plugs/wall worts or embedded within a device where they convert the AC from mains electricity into the DC that the electronic device requires. However, in the event of mains electricity failure (power cut) to maintain power to critical medical or industrial devices, an uninterruptible power supply can be used to perform the same AC or DC conversion but from batteries, supercapacitors, or flywheels.
In other applications, such as remote instrumentation or military, there may not be any AC mains available. Therefore, some power supplies use rechargeable batteries as their power source and convert the DC from the battery into that needed by the device (for example, a military radio, pager, or ground-based monitoring instrument). The military can also use power supplies to harness DC from a vehicle outlet or to utilize any AC or DC source.
What are battery chargers?
At a basic level, a battery charger is a power supply, but one that has been designed to charge a particular type of battery, or one that is complex enough to charge many types of battery. To give the simplest example, the most basic type of charger is one that charges a lead acid battery. It provides a constant voltage (CV) and either a constant current (CC) or a current limit. When the charger is connected to a battery, the current flows from charger to battery until the battery reaches a pre-set voltage, then the current starts to taper down towards zero to stop the charging. The most basic sort of charger does nothing else, although some will have a timer to stop charging after a set period. A more complicated charger has a multi-step design that may include pre-charge, bulk, top-up, and maintenance phases with each having a pre-programmed voltage, current and time. To function properly and safely, a charger must have the correct current and voltage, known as a charging profile.
Some chargers will also monitor battery temperature, via. a sensor inside the battery, to prevent or stop charging if the temperature is/or becomes too high. Temperature can also be used as a charge termination method, most commonly in Nickel Metal Hydride batteries where the change in temperature caused by the exothermic reaction can be used to detect when the battery is fully charged.
More advanced ‘smart chargers’ require communication between the battery and the charger. In this scenario, the charger becomes a programmable power supply where it is the battery that dictates the charging voltage and current, communicated to the charger over a 2-wire interface. The battery determines when it is fully charged and commands the charger to stop charging. The charger will also respond to alerts from the battery if it gets too hot. Smart chargers allow batteries of different voltages, capacities, and chemistries to be charged using a single charger, which can provide future proofing benefits.
Just as with power supplies, there are environments where battery chargers may not have access to AC mains, such as in military applications. Using military as an example, to make matters worse, there can be a wealth of equipment on the dismounted soldier that contains a battery and power failure in the field could have severe consequences, so charging batteries without AC mains can be a necessity. Therefore, solder-worn power management systems can be used to charge all the batteries in these multiple devices via. a single standalone battery whilst the solder is on-the-move.
When the soldier can stop moving or goes inside a vehicle, larger tactical chargers can be used, where standalone batteries or equipment (such as radios) are fitted into bays. Some tactical chargers are capable of transferring energy from one partially depleted battery into another partially depleted battery to produce a fully charged one. Tactical chargers can also harvest energy from renewable power sources like solar panels or wind, as well as connecting to AC mains or portable power generators where available.
Conclusion
Despite similarities, power supplies and battery chargers fulfil different but critical functions in environments where AC is either readily available or unavailable. Selecting the right power supply or charger for your needs depends on if AC mains is available, the type of AC or DC your electronic device requires, as well any required safety features.
Ultralife manufactures a wide range of power supplies and battery chargers, specialising in applications where power failure is not an option (such as industrial, military, and medical).
