The reason why this battery lasted this long is the very low current. 176 years x 365 days x 24 hours x 1 nanoamp = 1.54 milliampere-hours - that's nearly nothing. A modern phone battery (3 ampere-hours) would run over 342,000 years if the current consumption was only this low.<br>But what really is remarkable is that this battery seems to have very little self-discharge. The alkaline batteries I bought the other day have an expiration date of 2021. Then their capacity is only at 80% even if they've never been used. That makes a self-discharge current of already 13.7 microamps - Though this capacity might even be sufficient to deliver an extra 1 nanoamp for a bell for several years.,(reply>), It is now 2022, so how did they turn out?,(reply>), @Emmanuel Rodriguez That is not true. You are confusing batteries with and without built-in circuits. I have loads of 18650 cells from dead laptop batteries which still have +4v in them. Only the ones I have in rotation are used and charged. The rest where voltage tested when I disassembled them and put away for storage. They are still holding voltage fine, of cause with some self discharge but nowhere near dead at all. The ones I have with circuits will self discharge much faster if the terminals touch metal. If I put a non conductive spacer in or storebox, they hold charge much longer.,(reply>), heyy, ur batteries got expired!,(reply>), Did the batteries expire on-time?,(reply>), @Ryan Stallard Batteries can only hold so many joules of energy per cubic centimeter of volume. Energy is amp-hours * voltage. So, let's say for a given volume, a battery can only hold 2kWh of energy. If the battery is at 5 volts, then it will only hold 400 Ah of charge. If the voltage is 2kV, then the battery will only hold 1Ah of charge. That is why the voltage is important. If it is a very high voltage battery, it would have to be huge to store a large amount of charge as well. If it is a very low voltage battery, then you can store a bunch of charge in a reasonably sized space.<br><br>Or, put another way, let's say that a cell is 1 cm^3, has a potential of 1V, and has a charge of 1Ah, and let's say that the battery shown has a volume of 2000 cm^3. Well, the cells could all be arranged in parallel, which would give a voltage of 1V and a charge of 2000 Ah. Or you could arrange them all in series, giving 2kV of potential and 1 Ah of charge. Or you could arrange them into some combination of series and parallel, such as 400 groups in parallel of 5 cells linked in series, which would give you then 5V, 400Ah battery from above.<br><br>So, again, for a battery of a given size, if the voltage is very large, then it won't be able to hold a lot of charge.