I buy a new laptop battery from http://www.laptop-battery-chargers.com/toshiba-pa3536u-1brs.html we replaced the battery with the new 9 cell one . Unfortunately, the Toshiba laptop says that the battery is not connected. Sometimes when I reinstall the battery it says connected but not charging.....then will go back to battery not connected. I thought that this might just be the computer, but when I feel the charger it is not getting warm which is an indication that the unit is not charging. I then let the computer run on battery power until it when into sleep mode and then tried to recharge it. I received the same messages. I need help, any suggestions? When I put the old battery back in everything works fine.'
i contact the seller,they would like to resend me a new one,but i urgent
so any suggestion?

Had the same problem with my Dell laptop. Finally, after changing a couple of new batteries it worked. Infuriating but what can one do. Sometimes they have a mind of their own.

Well, for one, if you are good with a multi meter you can check to see if the contacts are working and charging. Check the laptop battery, the contacts of the unit and the contacts of the battery---make sure the pins have ample spring or resistance enough to make good contact (they get worn).

You can see if the unit runs the battery just on AC.

You can ask the client how old the unit is and if they leave the battery in every time they hook up to the wall as well---in this case the battery probably had all the life cycles it had available used up---especially if the unit has some age and/or wear or both. Some computer systems cycle through the battery even when the AC is used if the battery is not dislodged---this is still a wear on the battery and cycles it through what ever life it had---they only have so many.

More than likely it is a bad battery---or used up: More than likely if it runs on AC without the battery installed or with the battery installed and the battery just tests out with little or no current then it's just an old battery.

There is more but you get the idea. I’d check for known issues with the unit as well.

Regardless, I think it safe to hazard a guess that the battery is just dead if the criteria above have been met.

Other than that, yep, you can try another battery. I ever had a similar problem with my dell 1545 battery.

If you find something different then I'd like to know.

I hope this helps.
-Will