[jiml8]

In the recent past, I have suddenly encountered a LOT of threads and information that indicates a problem with the iPod mini battery.

Now, my daughter got an iPod mini for her birthday in August, so I am interested in this; I don't want to have to deal with what so many others are dealing with.

However, I have seen enough that I have formed a tentative hypothesis about the cause of the problem and a workaround for it.

Now, by background and training I am a physicist. I have worked with electronics, computers, and various types of complex systems for over 35 years. It also happens that I have flown radio controlled model airplanes for nearly 40 years, and that has caused me to acquire a considerable store of knowledge about the care and feeding of rechargeable batteries.

What I am seeing suggests strongly to me that the battery is being charged incorrectly by the iPod mini. This idea is not based on any hands-on testing and analysis; I have not torn my daughter's apart in order to study the charging circuitry. But the idea is consistent with the observed problem and it immediately suggests a workaround.

Modern rechargeable batteries are sensitive to how they are charged. More than likely the particular battery is a nickel metal hydride cell, and these can easily be overcharged - which will quickly kill them. Typically, these are charged by a pulse width modulation system that varies the duty cycle, turning down the effective charge rate as the battery charges and turning it off when the battery is fully charged.

If the charging process does not stop when the battery is full, the battery will be damaged.

Now, I propose that the iPod mini is using a rudimentary charging mechanism driven off the USB port, and is NOT checking - or not properly checking, or experiencing frequent failures due to a design flaw - and is therefore NOT stopping the charge when the battery is full.

This suggests that the best solution is to not leave the iPod connected to the computer for any longer than is necessary to charge the battery. In fact, it would probably be best to remove the iPod a few minutes before the battery is full.

If what I propose as the problem is indeed the problem, then doing this will greatly lengthen the life of the battery.

A friend of my daughter's has an iPod mini and also has an Apple cradle for it. This cradle turns it effectively into a boom box, as I understand it (I have not seen this myself). According to my daughter, her friend has had no problems with the battery in her mini, but it spends most of its life in the cradle.

Granting this is anecdotal, it could also mean that proper charging capability is built into the cradle and a mini so maintained will have its battery last.

I don't know; I am only guessing. My guesses are highly informed from a substantial and appropriate background, but they are still no more than guesses. If I wind up having to tear my daughter's mini apart, I'll hook up an oscilloscope and have a look at the charging mechanism, then I'll know more. But until and unless that happens, I won't know.

I have instructed my daughter to proceed as I have outlined here. It happens that she does not have the habit of leaving the thing plugged into the computer for long periods anyway, so perhaps her battery has not been substantially damaged. I guess we'll have a better idea in a few months.

[jiml8]

One addendum. If the battery is a lithium ion battery, then the details of how it is charged are different than the nickel metal hydride, but the effect of overcharging is the same.

[linskyjack]

Sounds interesting. I actually cracked mine open and put a new battery in. I am going to have my son put your theory to practice and see if he can improve the batteries life. By the way, if you are going to buy one of the replacement batteries and try to install yourself, I hope you have a steady hand, because removing the plastic end pieces is very difficult (they are glued) and there is so very little space between the plastic and the aluminum housing that it is almost impossible to remove them without marring in IPOD. My son's works fine now but he isn't happy about the cosmetic damage. I will keep you abreast of how things are going with your charging idea.

[applecrisp]

I didn't read the other posts but Im just gonna say apple need better batteries!!

Really annoying :eek