Naked Science Forum

Non Life Sciences => Technology => Topic started by: pirunner on 13/12/2007 02:03:41

Title: Reverse Charging Effect
Post by: pirunner on 13/12/2007 02:03:41

I have experienced the following with my cell phone AND laptop. That said, I have now learned my lesson, but WHY does it happen?

I used to leave my cell phone ALWAYS plugged in and charging. Some with the laptop. Both would be off. Eventually (like a year later)the battery life on both were close to NOTHING. My cell phone for example constantly sounds the low battery beep. Why would my charging have this REVERSE effect?

Title: Reverse Charging Effect
Post by: another_someone on 13/12/2007 02:27:47

Laptop batteries are notoriously short lived.

Old NiCad batteries (and to a lesser extent, NiMH batteries) needed to be regularly deep charged or they would have a memory effect, but most modern laptops and phones would use LiIon batteries, and should not have the same problem.

The problem with laptops (and I suspect maybe ultra compact mobile phones) is trying to squeeze too much power from too light a battery, so trading energy density for longevity.

Title: Reverse Charging Effect
Post by: daveshorts on 14/12/2007 11:15:21

I have been told by my brother who is an electronic engineer and had lectures on this sort of thing, that deep discharging Li-ion cells or definitley leaving them uncharged is bad for them, but I don't know the mechanism

Title: Reverse Charging Effect
Post by: another_someone on 14/12/2007 15:51:47

Quote from: daveshorts on 14/12/2007 11:15:21

I have been told by my brother who is an electronic engineer and had lectures on this sort of thing, that deep discharging Li-ion cells or definitley leaving them uncharged is bad for them, but I don't know the mechanism

Recently I something about this on the web - but again, don't know the background to it (don't even recollect where it was, or how reliable the source was).