Sony's batteries develop a problem over a period of time that isn't a "memory effect" but the net effect is similar - your camera shows the battery's got hundreds of minutes in it, then wham - it needs CPR. Likewise, when you charge it, it goes from flat to (a significant number: 90+? 200+? depending on battery) in just a few minutes.
If this describes the problem you're having, go to http://www.bealecorner.com/trv900/battery/lithium.html and have a read. The advice on this page has been duplicated on many other sites, so I guess it has some credence.
HTH

Hi Nick. At DVinfo we direct all "where to buy" questions to our sponsors, since they make the site possible. You can get genuine Sony NP-F970 batteries for $104.95 at B&H: http://www.bhphotovideo.com/c/produc...tery_Pack.html

Or Impact clones for $79.95: http://www.bhphotovideo.com/c/produc...n_Battery.html

I don't use my VX-2000 anymore, but I could get almost 8 hours run time with the older NP-F960 Sony batteries, so the 970's should really be champs. I bought two genuine Sony 960's in 2001 and one of them died in 2004. The other one just stopped taking a charge a few days ago, so I guess you might expect 3 to 6 years life based on this very unscientific experience.

This thread might also be of interest: http://www.dvinfo.net/conf/showthread.php?t=103435

ok, thanks a lot!

Sony NP570 Does Well Also
 

I never have to use my large NP960, as the small NP570 I got, lasts for more than 2 hours of shooting and that's more than I've ever needed. It doesn't poke out the back of the battery compartment, the way the larger ones do.

I know this threads a bit old, but I thought I'd help out.

There's a permanent vanadium-lithium battery that manages the functions of the clock and whatnot in the PD150.

It should be recharged by leaving the AC adapter connected for 24 hours with the camera power switch turned OFF.

If it doesn't, see pg. 157 of the PD150 User Manual for more options.