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I have a car key fob whose batteries recently died. The coin slot says it accepts two cr2025 coin cell batteries.

But I was thinking, since a majority of coin cell batteries run at 3v, I should be able to simply substitute the battery with the biggest capacity available. So in this case I could use a cr2032.
Fortunately, the bigger batteries fit in the key fob.

But are there any side effects to using bigger capacity batteries in place of smaller capacities?

I heard rumors that bigger batteries demand more current consumption from the load, or else the chemical reaction inside the battery will slow down, thus making the battery life shorter(assuming the load has a p-channel MOSFET to cut power from the load and a button to turn on the power).

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  • \$\begingroup\$ I would stick to the specs, even though I don't see any downside if it fits in. \$\endgroup\$
    – Eugene Sh.
    Jun 28, 2017 at 17:16

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If the thicker 2032 battery does fit into 2025 coin place of your key fob, there is absolutely no side effects. Your keyfob will just last longer.

The rumors you heard are utter nonsense. If a battery has no load, it means it is in "shelf", storage mode, and in the shelf mode no "chemical reaction" happens other than the normal storage aging , as in any other battery, 2016, 2025, 2032, or else. ("chemistry slows down", if you wish).

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