Unit will not charge - Black & Decker 15.6 Volt DustBuster Vacuum

always charge any item that comes with its own charger that way you can not damage it by trying to charge it another way.
there is always other ways to charge things up but its best to use what it come with (more so for safety reasons)

Bissell LIFT OFF 29H3 User Manual

Hi make sure the unit is charging by checking it with a tester , i am not sure of the voiltage when charging but if you look on the charger it will have the amount it should be charging the battery, if it is charging and your battery is not taking the charge then replace the battery

If the unit itself is under a year I would take it back to the store. It sounds like the unit is not charging properly which you already know. Check to see if you actually have charge coming out of your charger. Usually there is a charge light. Is it bright when charging? If you have a volt meter you can check the voltage coming out of the charger to verify if there is indeed voltage coming out. Let me know what you discover.

This unit is recharged using any household 120v outlet. Remove the rubber cap from the recharge port on the top of the unit. Plug the barrel end of the adapter cord into this port and then the put the adapter into the wall outlet. Make sure the power switch is in the off position. To check the charge level push the button to the left of the 3 indicator lights. When the green LED lights up, the unit is fully charged, (yellow is moderate charge and red is minimum charge).
Try to charge the unit from the minimum (red) charge level to maintain the maximum battery life and use of the product.
If you have misplaced the manual I am providing a link to it from Black and Decker's site.
http://servicenet.blackanddecker.com/documents/English/Instruction%20Manual/90550872,VEC010BD.pdf
Have a great day.
Jim

Most problems with what you have stated have to do with bad contacts between the hand held unit and the battery charger. With the charger unplugged, make sure the contacts on both the charger and hand held unit are clean and not bent. Check to see what the "Light Indicator" should be when charging and reinsert the unit into the charger. If the light does not show what it is supposed to show, move the hand held unit around a bit to see if you can make the connection better.
If this does not do the job, depending on the age of the unit, might be time to replace the battery.

Reset the Roomba: hold down "spot" and "dock/demo" for fifteen seconds, then release and listen for the tune. Then charge the Roomba overnight. The next time you run it, the unit should run longer. If not, call support and let them know you may have a battery problem. 1-877-855-8593 (I strongly encourage you to have the Roomba with you if you call.)

Its the battery cell, its dead and unable to hold a charge. you will need to purchase another cell.

Checked and found that motor is definitely overheating for unknown reason. Since power unit is still under warranty, solution was to contact local service company for NuTone power unit and have them come out and fix/replace it free of charge.

Same thing happened to me, I called the company, and they told me to remove the battery, press the on button for 5 seconds, which clears the system, replace the battery and do a long charge 12 hours. I'm in the process of doing that now.