I am attempting a DIY hack that involves (among other tweaks) replacing a battery pack with a PoE power supply. The battery pack in question uses 8 1.5v D-cells in a series-parallel configuration that produces 6v.

How do I go about figuring out how many amps my power supply will need to support? The device in question is an LED lantern, and the only likely-looking spec I can find is the marketing claim that 8 alkaline D-cells will last 32 hours on the high setting.

Also, am I correct in my vague understanding that amperage is generally a capacity, and thus more amperage is generally not harmful? Whereas too little amperage will result in a voltage drop? (I did study basic electronics in the military, but that was a very long time ago…)


1 Answer 1


Measure it. If you already have the device you want to know about, wire an ammeter in series with the existing batteries and find out the peak current needed.

Most multimeters have an inbuilt ammeter.

Here's a good guide.

Yes, the amperage rating of a power supply is the maximum current it can safely supply for the given voltage. Over-speccing your power supply should not cause a problem so long as you don't short it.


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