I find it convenient to just leave the charger sitting on my desk, still plugged into the wall, so that I can just pop the battery in when I need it, but I wonder if this is bad for the charger in the long term?

It doesn't appear to be doing anything without the battery in place, and it doesn't feel warm, but could there be any damage or even safety issues to consider?

I realize this may not be considered on-topic for Photo.SE, but I am interested in this specifically for my Nikon MH-18a charger and my EN-EL3e battery for my Nikon D90, though I suspect (hope?) that this will be of general interest to owners of other gear.

6 Answers 6


No, this is safe as long as the battery is not in the charger. Some chargers may have a small power drain from being plugged in (even when not charging anything), but it shouldn't do any damage to the device to leave it plugged in.

  • 1
    I agree. I leave one of my Pentax battery chargers plugged in all the time, never had an issue.
    – Joanne C
    Nov 1, 2011 at 20:29

It wouldn't harm the charger, but it is a good practice to turn off the switch and save power.

  • 1
    Could you provide supporting details? When I plugged my Canon DSLR battery charger with no battery into a power meter, it did not register any draw.
    – dpollitt
    Nov 2, 2011 at 1:13
  • depends on the device. Some may for example have a "standby" LED, which drains a few milliwatts.
    – jwenting
    Nov 2, 2011 at 7:18
  • Are there any chargers that can be switched off? I have more than a dozen chargers for various equipment, but none of them has a switch.
    – Imre
    Nov 2, 2011 at 9:55
  • I was talking about the switch for where we plug-in our charger :)
    – akshay1188
    Nov 2, 2011 at 11:11
  • Okay then, not all countries have switches on electric outlets :)
    – Imre
    Nov 2, 2011 at 17:00

As far as power drain is concerned, yes it will drain power. Will it harm your device has many other factors to it. Current will flow through transformer circuit. If you consider that as a factor that might harm your device, then it will.

Giving complete technical details will be a little difficult here, but i'll try to explain with links to detail.

A typical battery charger has two components:

  1. A step-down transformer to step down a typical 220/110V house supply to a lower value that can be fed to electronic circuit.
  2. AC to DC converter that can be fed to battery.

The transformer is a pair of inductively coupled circuit. Ideally (if the coupling is 100% inductive) if one end of the circuit is open (ie without any battery to charge), there should be no current flowing through the other end. But we don't live in ideal world and there is no load power drained from supply.

I wish i could have given more details but most of the readers will not be interested in that :-).

  • Transformer-based power supplies are almost never used in these types of applications anymore, although there are probably plenty of them still around on older devices. Mar 1, 2016 at 22:45

I imagine any electric component has a certain life span. When the charger is plugged in, even without battery, there's still some current flowing and some heat generating. However, the current and heat are minimal on stand by. So, I would answer: technically - yes, it is harming the charger, but practically - no, it isn't. The charger will eventually break anyway, whether you're using it or not :)

  • electrical components degenerate whether they have current flowing through them or not.
    – jwenting
    Nov 2, 2011 at 7:19
  • @ jwenting - also true. Nov 2, 2011 at 7:46

Unless it's a REALLY messed up charger, you shouldn't have any problems leaving it plugged in (I do it all the time :)). Like some other people said, it might drain a little power, so it's best to keep it unplugged. But, since the terminals aren't connected to a battery (or anything for that matter), then you should be alright :)



With some inexpensive aftermarket chargers, I would say potentially YES. If you listen - literally - to some of these chargers while they are unloaded, they sound like an SMPS circuit that is running far off its intended operating point (a bit like a speedlight that is near failing or hasn't yet fully reformed after a period of disuse), and the fact they make a sound also means that there is substantial vibration and/or electrical pulse stress load to some inductive or capacitive component. That does not make these components better.

  • Could that have been equipment that was faulty to begin with?
    – xiota
    Nov 12, 2019 at 4:38

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