Cell phone battery doesn't hold a charge

[cmosdes]

I recently bought a cell phone. I brought it home, played with it for a while, then noticed the batter was down to about 1/3 left on it so I charged it up. Within 2 days the battery was dead. I hadn't made a single call and the only time I took it out of sleep mode was to see how the batter was doing. I figured I had just not fully charged it so I charged it again, this time checking the batter meter and it was full. Once again, the battery was dead in about 2 or 3 days.

I brought the battery and phone back to the store and they exchanged them both. I fully charged the battery and again it was dead in about 2 or 3 days. I went back to the store and exchanged the battery again. They said to run the battery all the way down before trying to charge it up. So I did. Then I fully charged it and once again it looks like it will be dead in about 2 or 3 days.

This is a phone that should last for 18 days on standby. It is a Motorola Renew W233 phone. Any ideas what I could possibly be doing that the phone isn't holding a charge?

[Baracus]

How many bars are you getting at home? At work, my cell phone will vary between 0-1 bars and the battery will sometimes run down within a day. I always get a good signal at home and the battery will last a good week. It seems that the phone wastes a lot of juice trying to find a signal in my office.

[TroutMan]

I'm with Baracus on the probable cause. My parents have a place with poor cell coverage. Anyone who visits, their phone battery drains in a day or less, no matter how new or what kind of phone.

[cmosdes]

Interesting thought. I get no signal at my desk at work which could explain it. I hadn't considered that a cell phone would expend extra energy trying to find a signal. I'll just keep the phone off at work and see how things go.

[sevenwood]

Originally Posted by cmosdes

I hadn't considered that a cell phone would expend extra energy trying to find a signal.

My limited (and probably wrong) understanding of the situation is that to conserve its battery a cell phone will first attempt to contact a local cell tower at a low broadcasting power. If it can't locate a cell tower, it boosts its own broadcast power and makes another attempt. This process continues for (???) cycles until it's broadcasting at a fairly high power level in an attempt to locate a cell tower.

So if you're always near a cell tower your cell phone will generally retain a charge for its advertised interval. If you're not that near a cell tower, not so much - and if there are no cell towers available, your battery ends up fully discharged in a day or so.

When I had an AT&T cellphone and visited my mother in rural Missouri where AT&T had no coverage I had to either turn off my cell phone or recharge it every day or two.

[ChrisBooth12]

Whos your provider? With verizon dial a *228 to update your phone with new cell towers if they have been built after your phone was activated. Your phone tries harder to search for signals when it cant find any making the signal drain faster some (my tour) have an option to make it not even try if it cant.

[[Undecided] Adrian]

In addition to the coverage problem, there's also the possibility that you didn't wait long enough for the battery to reach its full capacity - it can take like 3-5 cycles (preferably with a complete discharge each time) to do that.

[chromaticity]

The Motorola Renew W233 uses a 910 mAH battery which is not so great, but it should definitely last you longer. From their website the standby time is 18 days, which is way more than you are getting even accounting for the conditions in which they measured it in.

You can increase your battery life by:

1. Putting your phone in flight mode when you cant get a signal.
sevenwood is exactly right, the phone keeps trying to get a signal boosting the power along the way. (Its why some phone manufacturers tell you not to block the antenna with your hand while calling)
2. Decreasing the brightness of your screen
3. Turning off Bluetooth and WiFi if you dont need it. (Maybe this phone doesn't have it)

Battery hysteresis is not such a big problem these days, but it would be nice to do at least a couple of complete power cycles with your battery before regular usage.

[gazpacho]

Phones don't transmit unless they can hear a base station. If the phone is not in listening range of a base station it spends more time with the radio on looking for a base station.

When the phone has found a base station the radio only turns on for a few hundred micro seconds every couple of seconds to listen for a message indicating that they have an incoming call or other message. The radio can be on only a short time because the phone knows exactly when to listen for the messages and at what frequencies to listen. Without being connected to the base station the phone must leave the radio on and search across frequencies trying to find a base station. That is where the power goes, keeping the listening portion of the radio on. Not transmitting information.

[TroutMan]

Originally Posted by gazpacho

Phones don't transmit unless they can hear a base station. If the phone is not in listening range of a base station it spends more time with the radio on looking for a base station.

...That is where the power goes, keeping the listening portion of the radio on. Not transmitting information.

Listening takes relatively little power compared to transmitting. Most phones will will go into a low power-usage mode anyway if there is truly no signal, only briefly scanning for a signal periodically. The real power drain comes when there is a weak signal, and the phone increases its transmitting power to communicate with the station.

[gazpacho]

Originally Posted by TroutMan

Listening takes relatively little power compared to transmitting. Most phones will will go into a low power-usage mode anyway if there is truly no signal, only briefly scanning for a signal periodically. The real power drain comes when there is a weak signal, and the phone increases its transmitting power to communicate with the station.

I disagree. The phone only very rarely needs to transmit anything. It only needs to transmit when it moves to a new cell or when it wants to initiate a call. The power drain comes from not sleeping because you are looking for a base station. When it does try and communicate with the base station it only transmits for a very short time.

[racer72]

My new Nokia phone needs to be charged every 2 or 3 days, according to what I have found online, this is normal.

[TroutMan]

My personal experience has been with no signal, the battery lasts fines. With a very weak signal, it drains rapidly. I think it transmits more frequently than you say, as it loses and re-establishes contact with the station.

I don't disagree that less sleep time will drain the battery faster, I just don't think this is the primary factor in rapid drain with a weak signal. Receiving a weak signal doesn't take more power than receiving a strong one. Transmitting to a distant base takes much more power than transmitting to something close.

[sevenwood]

...and if you really want to se your cell phone battery lose it's charge quickly, just purchase one of those Golf GPS apps for it. (This, of course, assumes that your cell phone has an internal GPS unit.)

Apparently constantly using its internal GPS unit takes a fair amount of energy. I barely get a full four hour round in before the battery dies on my Motorola W385 cell phone, and my golf buddy had to purchase a beefier battery pack for his iphone to get it through a four-hour round.

(Apparently under normal circumstances your cell phone only uses its internal GPS unit when you make a 911 call. I had to change an internal setting on my Motorola W385 before it would even let the Golf GPS app access its internal GPS unit.)

(The relevant apps are GPSGolfShot in the case of my Motorola W385 phone, GolfShot in the case of my buddy's iphone.

[Nametag]

I might add that Bluetooth will also drain your battery, though not as fast as a bad signal, or having 3G or GPS on all the time.

[cmosdes]

The cell phone I have is about as cheap a phone as you can get. As I mentioned in another thread, I rarely, if ever, will use the phone and I got one with minimum features. No bluetooth, no camera, no 3G.. just a phone with texting on it. I have it sitting at home where I get a very strong signal and I'll see how long it lasts in that mode. I'm not even sure I can change to phone to flight mode. I'll have to check on that. I'm hoping I can so I don't have to try and remember to turn it off before I come into work.

[Fear Itself]

Originally Posted by sevenwood

Apparently constantly using its internal GPS unit takes a fair amount of energy.

I will confirm this. I use Verizon Navigator GPS, and if I don't plug it in while I am in the car, the battery drains quickly.

[Mohamed F. El-Hewie]

The very definitive way to make your cell phone stay charged for three of four days is as follows:

1- Lower the intensity of Backlight (Tool/Display/Backlight) to minimum = 7 seconds

2- Lower the Brightness of Backlight to 2 out of 10
(slide the bar towards dark, away from bright)

Those two steps spare the great energy spent in illumination.

Done.

Mohamed F. El-Hewie

[md2000]

Cellphones handshake with the tower every few seconds.

There is a blank 144 characters in the 256-character handshake of digital cellphones, hence the 144-char text message limit to use that space in the handshake. Essentially, the phone companies would charge you 10 cents to transmit data they already had to transmit anyway.

As I understand, the cellphone will vary its transmission power - the closer it is to the tower, the less power it uses, so that the tower hears all signals equally loud and local signals don't bother nearby neighbour towers unless they are getting within range to switch. As a result, if you are in a location with poor or no coverage (or you store your cell in a metal locker, or your metal mesh room) it will be blasting at maximum power in an attempt to contact the tower every few seconds continuously until the battery dies a quick and painless drain.

The tower(s) take note of the signal and compare relative strength with neighbours to decide when to hand off.

The real reason the FCC did not want people using cell phones on airplanes was not because it would override the autopilot or such; it's because at 7 miles up, your phone will sound almost as loud to a dozen or more towers, crowding out other signals and confusing the hand-off mechanism. As was amply demonstrated on 9-11, cellphones work just fine in an airplane.

[phxjcc]

[quote=md2000;15489509]The real reason the FCC did not want people using cell phones on airplanes was not because it would override the autopilot or such; it's because at 7 miles up, your phone will sound almost as loud to a dozen or more towers, crowding out other signals and confusing the hand-off mechanism./QUOTE]

Exactly correct.

[engineer_comp_geek]

Originally Posted by md2000

The real reason the FCC did not want people using cell phones on airplanes was not because it would override the autopilot or such; it's because at 7 miles up, your phone will sound almost as loud to a dozen or more towers, crowding out other signals and confusing the hand-off mechanism. As was amply demonstrated on 9-11, cellphones work just fine in an airplane.

Originally Posted by phxjcc

Exactly correct.

Not quite correct, actually.

The FCC has two reasons that it bans cell phones on planes.

For the first reason, the above is actually kinda close. The problem with early cell phones wasn't so much that they would contact multiple towers simultaneously, but that they would access multiple cell systems simultaneously. The systems hadn't been designed with that in mind, and it caused them all kinds of grief. Systems crashed, calls were dropped, that sort of thing. Over the years the systems got better, and now that sort of thing won't happen at all. However, an airborne cell phone still ties up multiple channels on multiple towers, and the FCC doesn't like that kind of waste of bandwidth.

The second reason is that the FAA bans them. And the reason the FAA bans them is the potential for interference on aircraft systems. Chances are an airborne phone won't make a plane drop out of the sky. Most commonly, all it does is make annoying noises in the pilot's headset while he's trying to talk to the tower. Pilots aren't idiots and they are good at their job, so they can land the plane safely even if their headsets are all going wonky. Still, it's not a good thing to have, so the FAA doesn't want it. Cell phones have also interfered with navigation and communication systems. But for those who think cell phones are perfectly safe, it is also believed that a cell phone caused a thrust reverser to accidentally deploy during takeoff, causing a plane to crash. Airplane systems are intentionally designed to be resistant to this type of interference, but on very rare occasions, bad things can happen.

That's probably enough of a hijack, but worth mentioning since the above quoted text wasn't accurate. There are plenty of other threads on the board about cell phones and planes.

Getting back on track with the OP (note - two year old thread, expect zombie jokes) the backlight suggestion by Mohamed F. El-Hewie will help conserve battery life, but in my experience the biggest drain on the battery is the phone cranking up its transmit power because it has a weak connection to the nearest tower. That part of the above posts is absolutely correct and the only way to avoid that is to turn your phone off if you're in an area with poor connectivity, or just deal with the battery getting drained.

Basically, the cell phone is constantly talking to the tower. If it has to shout to be heard, it's going to use up its energy a lot faster.

ETA: Cell phones (while being less than optimal with bandwidth use) do work fine on airplanes, up until about 5,000 feet or so. This is due to the directionality of cell tower antennas. There's no use transmitting energy up into space when you can more efficiently transmit it out in the direction where a cell phone might actually be. Above 5,000 feet the chance of getting a decent connection get worse and worse, and once you get above 10,000 feet it's almost impossible for your cell phone to get enough signal to connect. All of the 9/11 cell phone calls were made below 5,000 feet, IIRC (maybe 7,000 feet, not sure off the top of my head).