Why does my battery die faster when it’s cold?

You know that feeling when you step outside on a freezing morning and immediately regret your life choices? Your phone battery feels it too. In fact, it’s even more dramatic about it. And if it gets chilly enough, it can be clinically dead at 20%. But why?

Your battery runs on chemistry, not hope

A phone battery works by shuffling ions between two internal layers. That movement is what gives the phone its power. When temperatures drop, the ions move sluggishly, like they’ve been forced to run a marathon after Christmas lunch.

The battery ends up with:

• higher internal resistance,
• lower available current output,
• and slower chemical reactions.

When you start using your phone, the battery tries to deliver the current your apps, screen and processor ask for. But because the cold has slowed everything, the battery cannot produce that current fast enough. And it shuts off.

Even if the battery technically still has charge left, it cannot deliver it at the speed the phone needs. This is why your phone may pretend to drop to 20% and die when you’re on a walk, only to bounce back to 30% once it warms up indoors. The charge was there, the battery just could not access it efficiently.

Is this why people refrigerate batteries?

Well, kind of. But also because they believe an outdated fact.

When a battery isn’t in use, it slowly loses charge through internal chemical reactions that happen all the time. These reactions are tiny, but over months, they nibble away at the stored energy. Cold temperatures slow these unwanted reactions too. So, if you put unused, traditional batteries (AA, AAA, camera batteries, etc.) in a fridge, the rate at which they self-discharge drops. And this can extend their shelf life.

So, they’re not trying to get more power out of the battery while it’s cold. They’re simply keeping it cold when it’s passive and warming it back to room temperature before use.

With old battery chemistries like nickel metal hydride, this made a bigger difference. With modern lithium-ion batteries, self-discharge is already very low, so the benefit is much smaller, and you’re generally advised not to refrigerate them because condensation can ruin them.

Can I stop my battery from acting like that?

Mostly, yes. How?

• Give your phone your body heat. Keep it in your pocket, not your bag.
• Use a case that gives it some insulation.
• Avoid charging it in low temperatures (yep, no powerbanks).
• If you can, warm it slightly before using it.
• Turn off/close any unnecessary battery-eating features.

The good news is that once temperatures go back to civilised, your battery life will also return to normal. So, be kind to your phone and remember that it’s simply trying to survive winter like the rest of us.