Does a weak cell signal affect phone battery life? How much?

I’ve heard that if you’re getting weak signals for either wifi or cellular networks, it can affect battery life. Something about how with a weak signal the radios will be, I don’t know, cycling through channels or something, trying to improve the signal. I’m sure my explanation isn’t accurate, but is the result actually true, and if so, is it significant?

My boring reasons for asking:
My iPhone 4S only gets about 4-5 hours on a charge now, which could certainly be from iOS 7, or just that the battery is about two years old now, or a combination, but even before noticing a recent the recent reduction in battery life, it always seemed to just barely make it through the day. So as I try to find a reason for that, and look ahead to replacing it, I was wondering if the fact that I get terrible cell reception most of the day is a significant factor.

I’m on Sprint. During the work day at my desk I’m not on wifi, and the cell signal is reporting between 2-3 bars, or blips, or whatever they are now. At home I have a strong wifi signal, but cell coverage is even worse, from 1 to 3 bars, and often dropping off Sprint onto the extended network if I’m downstairs.

I knew Sprint was probably going to suck when I picked it 2 years ago, but I stuck with it because it’s the cheapest option for unlimited data. Unlimited, terrible data, barely adequate for streaming music around town even on 3G, with no LTE anywhere near me, but for whatever reason, I can rationalize that and will probably stick with Sprint for the next round, except for this battery thing. If my weak cellular coverage really is going to make a big difference in battery life, I think that might be what it finally takes for me to shell out for better service. Can anyone point me to some info on this?

My phone drops about 5-6%/hour just sitting around screen off at home (decent wifi, 0-1 bars of cell signal) compared to 2-3% at work (better wifi, 1-2 bars of cell signal).

It’s anecdotal, but I’ve heard the same things you generally have. Bad signal is going to make the radios work harder, and particularly before the LTE/3G divide was crossed (in 2011/early 2012, many phones with LTE had a fully separate LTE chip put in to access it, causing double power drain as it had to operate alongside the standard radio for other signal types), radios can definitely drain battery.

That said, screen on and rogue apps will consume far more in a general case.

I also keep Bluetooth on all the time because I’m always using it in the car, probably about 45-60 minutes of driving a day. To me, that seems like it should fall well within normal use of the phone, but I mention it now because it just occurred to me that maybe average users still don’t really use Bluetooth for much. It’s fun to try to figure all this out anecdotally!

Cell radios (most, probably all) have a variable amount of power draw. When they have a strong signal they reduce their power consumption (the amount varies by manufacturer and software version). As your signal gets weaker they increase their power, to stay in communication. This is a simplification of the algorithms but close enough to be accurate for a general consumer.

Just curious, how do you know there’s no LTE around you if you’re using the 4S, which has no LTE radios?

I mention it because LTE will give you around 10-15% better battery life on the 5S. If you DO have LTE where you work, that’s a good reason to upgrade right there.

Going by Sprint’s coverage map. I mean, you’re right, it wouldn’t have mattered either way in the last two years with my 4S, I was just stressing how unappealing they are as a carrier for everything except price.

I just dropped Sprint for T-Mobile. Oh what a feeling!

Weak signal definitely affects the battery a lot, although I can’t quantify it. :)

About unlimited. Analyze your usage over the last year, see how much data you actually consume, maybe unlimited data is not worth holding on to?

If you regularly use your phone(like a a full charge a day) then after 2 years your talking about hundreds of cycles. Getting 5 hours now sounds about normal I’d think.

You’re probably right, but I still have a hard time justifying it. I signed up with Sprint through some weird referral promotion I don’t think is offered any more, so right now, my bill is $70 (plus the few bucks in fees, so around $75) for unlimited text, data, and I think 500 minutes or so of talking (signing up for Sprint now would be $80 for unlimited everything, so still the cheapest). I use about 2GB of data a month, and the Verizon 2GB plan is $100, or $110 for the next step up to 4GB if I want a little breathing room. I could afford an extra $40 a month, but I really don’t want to. Like I said, Sprint’s coverage, at least in my area, has always been just barely tolerable, but I’ve stuck with it for the savings. It probably also helps that I’ve never had a 4G/LTE phone to know what I’m missing.

The value of Sprint’s pricing compared to service still something I reconsider frequently, so that’s why I was checking to see if the battery life is another factor I should seriously weigh when considering carriers for my next phone.

I made sure not to plug my phone in at my desk this morning to see how long it would last, so from fully charged this morning, it just shut off a moment ago. Plugging it in and checking the settings, it says I had 2 hours 43 minutes of usage, 5 hours 20 minutes of standby time. And it shut off with no warning, reporting around 34% charge left. So yeah, I think this battery has about had it.

edit: Hah, I’ve got 4 days left of AppleCare+ support, I was misremembering when I signed up, so I’ll at least try to see if they’ll replace the battery. I’ve heard that’s kinda hard to convince them of though.

Wow, that’s pretty terrible for a 4S. That’s the phone I’m still using, and I can still make it through a full work day and a bit of the evening before having to plug it in. With moderate use, i.e., not much gaming, and a lot of reading RSS feeds and Qt3 over both WiFi and 3G. I hope AppleCare will do something for you, but if not, you might be better off getting a battery case like the Mophie Juice Pack. Or, even better since you’re likely to upgrade to a non-4S form factor soon, a portable USB battery pack (The Wirecutter likes this one).

If a “genius” asks me if I force quit my apps I’m going to go outside, take my clothes off, throw a chair through the window, and set the place on fire.

You should just Force Choke the “genius”.

AppleCare+ comes through with a free battery replacement! And no condescension from any employees!

So that’s some relief for the immediate battery situation with my 4S, but I’m still close to abandoning Sprint when I upgrade in a couple months.