## Thursday, January 22, 2009

### Cell phone battery and the fridge

A month ago, during the 0 °F cold snap, it looked like my cell phone whose (18 months old) battery used to last for 10 days at the very beginning got discharged after 2 days or so. Even with a new battery (not from the same company but arguably having the same capacity), the energy disappeared quickly. What would you think was the reason?

I decided that the cold weather could have something to do with it. When it's cold outside, the energy from the Li-ion battery is not released efficiently and some circuits might think that the battery is already getting empty. However, the battery emptied itself in 2-3 days even when the cell phone was kept at home, around 20 °C.

This looked hopeless. Maybe, the cell phone is not being charged completely, because of some memory effects or a wrong idea about the voltage needed to have a full battery. But if there is a mistake based on a wrong calibration, the argument above must be revertible: if you recharge your cell phone in the fridge, the circuit must think that it's not yet full, and it will try to charge it more fully than if the recharging occurs outside the fridge.

I tried to charge the cell phone in the fridge and indeed, it seems that the lifetime has been extended, at least to 4 days (and counting). Do you think it's possible, reproducible, and that my explanation is correct? Do you need to be a chemical engineer who studies Lithium batteries to give me a sensible answer? ;-) If you agree with my method, is the battery fixed for another year or do I have to charge it in the fridge all the time? Will it work? Can I recommend it to others to fight the aging of their batteries?

Dramatic update

Unfortunately, I have bought a new battery.

However, when I turned the "Cell Info" (Czech: "Informace o buňce") service off, the lifetime between two recharges went from 2.8 days to 11.8 days (assuming the same light usage)! The "Cell info" service is showing the location of the closest "cell" - your location (i.e. your neighborhood) on the main screen of the cell phone. However, it needs to communicate with the "cell" frequently which consumes the energy very quickly.

#### 3 comments:

1. Great blog,congrats on the 2008 award.

2. Fantastic blog. Kudos and congratulations.

3. I think you have to never do such kind of experiment in your house. There can be possibility of any mistake done or you are harmed with unobvious thing.