Curiosities: Why batteries lose their spark

Last weekend, I grabbed my cordless drill to hang a few shelves, only to find the battery gave up after 10 minutes. It used to last an hour. Had I done something wrong or do batteries really lose their spark with age?

The truth is not mystical at all. Rechargeable batteries, whether in power tools, mobile phones or laptops, store energy through chemical reactions. Every time you charge and discharge them, the materials inside expand, contract and slowly break down.

In lithium-ion batteries, the kind most of us use now, chemical deposits gradually build up on the electrodes and tiny structural changes occur that trap lithium ions or prevent them from moving freely. That wear and tear means fewer ions can shuttle back and forth, so the battery holds less charge than it once did.

Heat, cold and long periods of disuse all speed up the decline. Storing batteries fully charged or completely empty also shortens their life. Ideally, keep them at around 40-60% charge if you are not using them for a while. So yes, your old drill battery really is fading and your laptop’s will too eventually.

To make them last, keep them cool, avoid leaving them plugged in unnecessarily (though modern devices often manage this automatically) and use them regularly. Old batteries do not lose their memory; they lose their chemistry.