My Phone Died at 20 Per Cent in Spiti

Kunzum Pass is more than four and a half kilometres up, and the wind there behaves as if it has a personal grudge. Papa stopped the car so we could see the prayer flags snapping against a sky so blue it looked fake, and I climbed out, took off one glove with my teeth and lifted my phone. It said twenty per cent. It showed me the camera for exactly one second. Then the screen went black.

I pressed the button. Nothing. I pressed it again with the kind of force that has never once fixed anything. My sister, who had been asleep for most of Lahaul, opened one eye and said, “You should have charged it,” and closed it again.

The odd part came an hour later, lower down, in the warm car. I had given up and put the phone in my jacket’s inside pocket, mostly so I didn’t have to look at it. When I took it out, it switched on. Twenty per cent. As if nothing had happened. As if it hadn’t abandoned me at the single most photogenic spot of the whole trip.

So I asked Papa, who designs the wiring for buildings and therefore, in our family, has to answer every question with a plug at the end of it.

A phone battery, he said, doesn’t hold electricity the way a bucket holds water. It holds lithium. When it’s charged, lithium has been packed into the layers of graphite at one end. When you use the phone, lithium atoms give up an electron each and drift as ions through a liquid called the electrolyte to the other end. The electrons can’t go through the liquid, so they take the long way round, through the phone’s circuits, and that flow of electrons is the current that runs everything.

The trouble is that every part of that journey slows down in the cold. The electrolyte gets thicker, so the ions wade instead of swim. The reactions at each end, where lithium has to let go of an electron or pick one up, happen more slowly, because fewer of the jostling particles have enough energy to get over the hump. Together, Papa said, all that sluggishness shows up as something electricians understand very well: resistance, inside the battery itself.

Then he drew it on the back of the toll receipt. A battery’s voltage at its terminals is what its chemistry can supply, minus what it loses pushing current through its own insides. Small current, small loss. But a phone doesn’t ask for a small, steady current. When you open the camera, the processor wakes up, the screen brightens and the image chip starts working, and the current jumps. With the battery’s inner resistance raised by the cold, the loss jumps too, and for a moment the voltage dips. The phone keeps watching that voltage. Lithium cells are damaged if they are drained too far, so below a set level the phone decides the battery must be empty and shuts itself down to protect it.

“So it wasn’t empty,” I said.

“It wasn’t empty. It was cold. It just couldn’t hand over the charge fast enough.” In my pocket the battery warmed up, its resistance fell, and the same twenty per cent was usable again. Nothing had leaked away. It had been there the whole time, stuck behind a traffic jam.

He added one more thing, which I’ve since found out is true and important: if a lithium battery is very cold, you shouldn’t charge it. Push lithium back in too fast when it can’t slip into the graphite properly, and some of it plates onto the surface as metal, which never comes back out. That’s why some phones won’t charge at all when they’re freezing.

For the rest of the trip my phone lived inside my jacket, next to me, like a small, warm, unreliable pet. I came out only for photos, took them quickly, and put it back. At Chandratal, the lake was the colour of a peacock and the phone said nineteen per cent, and it stayed on.