I want to replace the battery.

the 2007 DV batteries are NLA from HP and have been for 15 years, so no new packs from HP - even the many clone OEMs stopped making them years ago though some still do.

These laptops have a big reason why: I don't know if you were around for this, but this era was infamously for GPU failures years ago where nearly all of them died in 12-18 months from bad GPUs, so very few still work today. This basically makes it so the batteries left are expensive compared to others without rampant failures, or current models -- or the battery you bought is NOS on a shelf from 5 years ago. They are readily available on Amazon but the prices vary wildly so keep that in mind: https://www.amazon.com/hp-dv6500-battery...

While you can still buy batteries, they are borderline extinct and are significantly more expensive then the current street value of these laptops (basically scrap, nobody buys them). Anything from this generation left that works is a ticking time bomb - buy something new as soon as possible. I have the F500 Compaq variant and it somehow works, but I got it in a junk lot and trust it like a fart so if you have a working unit, nobody buys a battery - we use it with the dead pack and not put a dime into them. Yes, my pack is stone dead and no, I will not buy one for it because of how unreliable they are.