Why do my batteries suddenly discharge?

Question

I have a Dell Latitude D520. It's a little over a year and a half old. I started noticing something strange going on with my battery... it would discharge normally to about 40% then drop down below 10% instantly. I figured I needed a new battery, so I bought one. The new battery is doing the exact same thing now. To better illustrate what I'm talking about, I logged the battery Discharge Rate, Remaining Capacity, and Voltage while I let it run from 100% charge down below 5% where the status was critical and Windows hibernated.

Here's the graph...

http://img181.imageshack.us/img181/4269/batterydischargeqp7.jpg

This is happening with the old battery as well as the brand new battery. As you can see in the graph, the Discharge rate was fairly constant... there's no spike there that would have drained the battery... the capacity just dropped like a rock, from about 40% to 10% then seems to resume normal operation from about 10 to 5%

Any ideas what's going on?

Here's the graph of the other battery recharging...

http://img232.imageshack.us/img232/2637/chargingoriginalty8.jpg

I have tried recalibration... from what I understand, that entails completely discharging the battery, then fully charging it, correct?

Answer 1

Hi. Have you tried a battery recalibration? Many sites explain how this is done. My Dell has a similar problem and I have yet to figure it out. Drops from about 30% to empty very quickly.