Nikon EN-EL9 Battery

I lost my battery charger. I'm thinking of getting an aftermarket charger because they are cheaper.

I'm wondering what does the S stands for on the battery?
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Do they need to be charged as well? Like is it used to get the battery charged? Since there are three pins n the charger.
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because the one i'm planning to get doesn't have that, only two - for positive and negative.

Please answer!

Learn how to post links we can click on, please!
These things are cheaper for a reason. Cheaper quality.
Buy Nikon!

The third pin is for internal circuitry that senses the battery's charge and for controlling charging. If the charger you plan to buy has only two pins, you risk it not working, or damaging your batteries. Sometimes buying cheap doesn't turn out to be cheap in the end.

Spend the little extra and by the Nikon charger.

Third party chargers have been known to overheat batteries with can reduce the life of the battery and in extreme cases catch fire or even explode. One with only two pins surely falls into that category of chargers

That third pin communicates with the battery so that it does NOT overheat and so that the charger will shut off once the battery is fully charged. Think of the extra cost as insurance.

I agree with the rest of the answers that you'd be better off with the NIKON, I picked up a third party charger after my Nikon branded one died and it does a decent enough job, it has a light that lets you know when the battery has been charged I wouldn't leave any charger that's actually charging batteries unattended, best to keep an eye on them and unplug them after they have done their stuff.

You only need two pins to charge. The third one is for data. I'm not sure about how Nikon uses that third pin. To be safe, don't get the cheapest charger.