How do I change the battery pack on a PHV1800 black and decker dustbuster

Carol, Black and Decker USA Factory-Reconditioned CWV9610R Dust Buster 9.6V Cordless Wet and Dry, does sound like you got a bad battery in the unit, replace battery or return if warrantied.
https://ca.answers.yahoo.com/question/index?qid=20070525003616AAhjgrS

Black Decker CWV9610 DustBuster 9 6V Cordless Wet and Dry Hand Vacuum

96V Wet Dry Cordless Hand Vac

DUSTBUSTER 9 6V HAND VAC

Either the battery pack needs replaced or the charger is not working correctly.

it is probably the brushes on the motors are wore out or stuck and not making contact. pretty much junk unless you feel confident enough to attempt repair.

If you need further help, reach me via phone at https://www.6ya.com/expert/steven_a67ead41eb5fc62a

if you've changed filters and checked for blockages it may need a new suction fan ,,you can download the diagram off the link below
http://www.ereplacementparts.com/black-and-decker-phv1800-dustbuster-parts-c-4167_8887_8897.html

I had the same issue, then i just found the manual, in charging part, it says:"The charging indicator will be lit as long as the
appliance is connected to the plugged-in
charger."
Also it says:"While charging, the charger may get warm, this is
perfectly normal and safe. It can remain on
charge indefinitely without damage or danger. It
is not possible to "overcharge" the battery cells
with the charger provided"

I have bad news. That part is no longer available; check out the info here:
http://www.ereplacementparts.com/black-and-decker-fve9610-dustbuster-parts-c-4167_8887_8911.html
I actually have exactly this kind of dustbuster, and I was able to renew the battery pack, but I had to do it by using eight individual cells and soldering them together. The size of cell (I think it's called a sub-c) is not common to consumers, but is fairly common to battery pack manufacturers. Quite honestly, your dustbuster with no battery is worthless, even when it was available, the pack was $46.46 as a spare - probably more than the thing is worth. Buy a new one from wal mart! If you really, really want to look at getting a new pack for this one, then your only option is to find a specialist battery store (I know there's one in my city) that can 'remanufacture' them. Basically, they take the old pack, and rip out the old cells, and put in new ones. They have the special equipment to weld the connections without frying the cells too, and they have access to Sub-C cells, of course. It'll be expensive. Good luck, you're gonna need it. Sell it at a garage sale; it looks nice.

If you are handy with a soldering iron, and don't mind spending a few hours building a new battery pack using 1.2 volt "sub c" cells, you can disassemble the PHV1800, and rebuild the pack yourself. I just did it tonight, and the vacuum works like new.

However, I'm not going to do this again. The PHV1800 doesn't use a single battery pack, but 2 packs that have to be assembled with very little room for error. You can purchase a combination battery pack/motor assembly for $75 (US currency, price currect as of 10/2011), unscrew the screws that hold the vacuum together, and replace the battery/motor unit as one.

If you are handy with a soldering iron, and don't mind spending a few hours building a new battery pack using 1.2 volt "sub c" cells, you can disassemble the PHV1800, and rebuild the pack yourself. I just did it tonight, and the vacuum works like new.

However, I'm not going to do this again. The PHV1800 doesn't use a single battery pack, but 2 packs that have to be assembled with very little room for error. You can purchase a combination battery pack/motor assembly for $75 (US currency, price currect as of 10/2011), unscrew the screws that hold the vacuum together, and replace the battery/motor unit as one.

Hi pwolft...
Amazon offers pretty large number of black decker replacement batteries, click here Finally charging for our multi device world and pick one (which fits).
Hope this was helpful.
enjoy

Leave it in the charger for at least 7 hours and then try and see if it works on a full performance time of roughly 3 minutes.