Adventures In Computing: Mystery of the Rapidly Draining Phone
For a while now, I’ve wondered why my phone charge was losing ~2.5%/hour. Even when not really doing anything. Not that it was a problem. When the battery got low, I just turned on the power strip it sat plugged in to. Spoiler, I just gave away the cause.
The Dilemma
A number of years back I got a new phone. While I didn’t bother nailing it down at the time, it felt like the battery was draining rather quickly. But my usage model had it easy enough to charge. Whenever needed, just throw the switch. Sure, I had to do that every day or so. But it was no big deal.
Yes, using my phone a bunch would drain the battery faster. But just sitting there, idling as it were, seemed to drain it faster then expected.
The Observation
Then I was visiting my parents for about a week. I charged my phone up before leaving. And didn’t need to charge it while there. Mind you, with all the other activities I didn’t realize it at first.
Once I did, I tested a few times. Confirming that I was using battery charge at the rate of ~2.5%/hour when at my residence. But when visiting parents, it was something around 1% every 4 hours. I’ve got less data on that side, but the difference was both significant and obvious. The cause though, that took a bit to figure out.
The Considerations
My first thought was signal strength. My parents place is out in the country, farther from the nearest cell tower then my place. Was the phone using… less charge for a longer signal? No, that would be silly. Plus, my phone is in airplane mode essentially all the time. Whether at my place or elsewhere.
If not the tower, might it be the distance to the WiFi router? My router is across the room, with nothing but open air between it and the phone. At my parents, the router is through a pair of walls and maybe a few feet farther away. Meaning that it should take more power at my parents. Another idea that didn’t fit.
Might it be the WiFi signal? Again, my parents have some distance to their neighbors. So the only WiFi signal is from their router. Whereas my place has neighbors nearby. Seeing a dozen WiFi networks is not unheard of.
Was the quantity of networks overwhelming the signal, thus needing more power to broadcast? Perhaps, but how to test. Using a tool I checked for what channel the various WiFi networks were using. Most of them were clustered around a pair of channels, leaving the rest unused. Seemed like a plausible explanation. So I tried changing my routers channel, and tracking battery charge for a few hours. A few days later, once I had tried all the channels and gathered the data, the answer was clear enough. No, channel was not making a difference. At least not an appreciable one.
The Discovery
For a time then, I gave up. It wasn’t critical, charging was easy enough to do every day or so. And I was out of obvious things to check. Although the question was still in the back of my mind, and I would think about it occasionally.
Because something had to be different. It was the same phone. It was the same settings. I made sure not to change anything, just unplugged my phone and left. While the infrastructure at both locations was different, that shouldn’t really matter. Especially when I tested what I could.
Then one day, while packing up to leave, as I unplugged my phone, I realized I don’t plug it in at my parents. Not unless I’m charging it, which almost never happens there.
I didn’t do anything with that insight until I got back from that trip. But when I did, it made for a simple test. Put the phone back on the desk, just like usual. But don’t plug it in. Note the charge level, then come back in a few hours.
It took ~6 hours before the percentage went down 1. I then tested both ways, just to get enough data to be sure. Conclusion: Plugging my phone in leads to faster battery drain. The mystery of what is causing my phone’s battery to drain so quickly was solved.
The New Mystery
Mind you, that just led to the new mystery of why plugging it in mattered.
I don’t have any good ideas for that. Plugging the phone in connects it to a power strip and a keyboard. I wouldn’t expect the keyboard to use much power, especially when it’s sitting there unused. And the power strip isn’t doing anything. Yes, if something else was plugged into the power strip, I could imagine it draining power. And at times, other devices are plugged in. So there are a number of wires hanging off the power strip.
Which I suppose could be the answer to that mystery. Does a random assortment of wires slowly drain power? Even if they aren’t hooked up to anything on the other end? I don’t know, that’s well outside of my electrical expertise (or lack thereof).
In the end, that detail doesn’t really matter. It’s easy enough to only plug in the phone when I want to use the keyboard or charge it. And leave it unplugged the rest of the time.
And with that simple change, battery life is up to the point I only need to charge once a week or so. Quiet the difference.