Hey all, Was hoping someone could shed some light on this mysterious situation for me. I have a Dell Inspiron 8100 Laptop. I've had it since 9/2001. My original Li Ion Battery started going out about a month ago, meaning it barely holds a charge for 20 minutes now when running on it, so I bought a new battery. I got a newer model battery since they have changed in the last year and a half. I got the new 4460Mah Battery that lasts longer than my original one. The new one will last me an average of about 3 hours depending of course on what I am doing. Here is the interesting part: My Laptop has a slot for both batteries. So just for fun I put both my old and new battery in to see how long they would last. I expected to get maybe 3:30, the time I have with each battery invidually, but instead I get about 5 hours! It seems somehow by using both I get alot more power from my old battery and the system drains them both slowly rather than one, then the other like I figured it would. So I'm getting alot more juice that I expected. I'm just wondering, is there any downside to doing this? Could using the old battery with the new one hurt it at all? I just spend $100 on the new one and just don't want to go out again soon having to get another. Thanks for any input. This has got me quite curious.