Do You Need a Power Supply or a Battery Charger?

Custom Battery Charger

The terms “Power Supply” and “Battery Charger” are often used interchangeably, but they perform distinct functions.

A power supply is designed to supply a constant voltage to a load. As the load requirements change, it continues to supply a fixed DC level.

A true battery charger generally supplies a regulated current, first to charge the battery, and then switches to a regulated voltage mode. This is specifically required for Li-Ion chemistry where overcharging is not only damaging to the battery cells, but can also pose a possible fire hazard. A smart battery charger will not only never overcharge cells, but can also monitor battery temperature, switching off a fast charge when certain parameters are exceeded.

A power supply used as a charger cannot do this, and will continue to pump energy into a battery regardless of its condition; fully charged, battery fault, or shorted cells.

In order to achieve maximum battery service life, a properly designed charger should always be used to charge cells.

2 Replies to “Do You Need a Power Supply or a Battery Charger?”

  1. Can a 6 volt power supply which is designed to be used to charge a small wine bottle opener (which uses 3 ni-cad batteries) be used to charge a 6 volt dry-cell (I guess) hand Coleman air compressor.
    The power supply is rated as output 80 mA and measures a 6.25 volt output.
    The transformer is rated at 7.5 volt output
    I ask this question because both the power supply and the transformer have the same output male plug!
    Also, are DC outputs from power supplies measured differently transformer outputs? I have long wondered about that!

    1. Hi Dan,
      Ni-Cad batteries have their own charging profile, which might not be suitable for whatever type of batteries your compressor uses. We would not recommend using it for other than it’s intended purpose.
      Generally, outputs from power supplies are well regulated over line and load, whereas transformers are very sensitive to input line, and to a lesser extent output loading.

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