My phone battery went from lasting all day to dying by mid afternoon, and I assumed it was just old age. Then I borrowed a friend’s cable for a weekend and my battery life suddenly came back. The cable had been the problem all along.

A bad charging cable does not just charge slowly. It can actually wear your battery down faster.

The signs of a cable gone bad

Before you blame your phone, watch how it charges. A failing cable gives itself away.

• It charges slowly even when plugged into a good wall adapter.
• The connection drops if you move the phone slightly, so you have to find a magic angle.
• The cable or the plug gets hot while charging. That heat is a warning sign.
• The metal end looks dark, corroded, or wobbly.

That last one, the heat, is the dangerous part. A cable with a loose or worn connection creates resistance, and resistance creates heat. Heat is what degrades a battery over time.

What to actually buy

You do not need the fanciest cable, but you do want one that is properly certified. For iPhones, look for MFi certification on the box. For anything USB-C, a cable that meets the USB standard and is not a dollar store knockoff.

The dead giveaway is price. I bought a pack of three cables for the price of a coffee once, and all three were garbage that charged slower than the phone drained.

My rule now: if a cable gets hot or needs the magic angle, it goes in the recycling. A twenty dollar quality cable is cheaper than a hundred dollar battery replacement.