Instant draining of cell phone battery - what's the cause?

I am just curious: occasionally, my cell phone battery will go from a partial charge, say 2/3 charged, to absolute zero dead, with no warning. Is this a fault of the battery, or is the phone somehow mysteriously instantly sapping all the energy out of it? It has happened with more than one battery, though none have been new batteries. Normally, it just runs down little by little. I have an old Motorola Rizr Z3.

You may just be getting an incorrect charge reading… not sure if the phone’s software calculates that or if it just passes the value along from an IC on the battery. I’ve had phones that were extremely optimistic about battery charge, and it sucks.

Could also be the phone had been in near standby for some time and perhaps the battery appeared to be in a better state of charge until some load was put on it like activating the RF deck by making a call or something along those lines.

It might be the memory effect.
If you keep charging a battery before it needs to be charged
the battery can stop being capable of holding a charge below that
The phone doesn’t know about this new limit on its power supply,
so it can’t show how much of a charge is left.:smack:

Cell phone batteries are usually lithium and do not have a memory effect.

NiCad are the ones with memory effect and completely draining them will rectify that effect. All batteries to the best of my knowledge do better being maintained at a high charge, and draining them completely shortens their life.

Battery University - Memory: myth or fact?

Your battery has reached the end of it’s ability to hold a charge, it’s time for a new one.

This is why Santa brought the Mr a new battery for Xmas, for the exact same phone.

Worked a charm, issue entirely resolved for $40.

NiMH can develop memory as well, a simple complete discharge will not necessarily resolve memory that’s developed in a NiCD. Regular, complete discharges, and regular, complete full charges are what are needed for NiCDs, and they need a regular reverse-voltage conditioning cycle once in awhile as well to alleviate formation of crystals on the plates.

My new battery arrived two days ago. $6 on eBay (new).

My phone started doing this a month or two ago - turned out it was the new (and bloody expensive) holster case I’d bought for it.

The case had a big metal spring clip to attach it to the belt and a big flat piece of polymer magnet to close the flap - one or both of these features must have been blocking the signal, causing the phone to ramp up antenna power to maximum, draining the battery in a very short time. Different (cheap, velcro closing) case, battery as good as new.

I understand that those devices/covers designed to (suppposedly) protect the user from (supposedly) harmful radiation do pretty much the same thing, except on purpose.

ETA (I also reported lionshining’s spam post above mine)

Relevant Straight Dope column.

And I’m pretty sure it applies to lithium, thought to a much lesser extent. In particular, I’ve seen a problem with people who keep their phone plugged up in their car while they are using it. A friend who works at a cellphone company says that this is often the reason phone batteries wear out before they should. Then again, I would think that, if this was common, the phone should know to stop charging when it is actually in full use.