I bought a transformer prime for my Mom for Christmas. She did not have any problems with it until I got the asus keyboard/docking station for her. Every time we have connected the keyboard to the tablet the battery charge goes dead in a short time. Now we've just quit using the keyboard so that she can use the tablet. This seems to be a waste of my money, as I bought it to extend the battery power. We have made sure the tablet is locked in securely. What could we be doing wrong?
Welcome to the forum :)
Sadly, it sounds to me as if you have bought a faulty dock as it should "just work". However, here are some troubleshooting routines to work through for you...
1. Charge the tablet only for 8 hours
2. Charge the dock only for 8 hours
Now use the combination together. Get the app dual battery widget from the Play Store (there is a thread all about it in the Battery & Charging guide thread which is linked from the Master Help Guide in my signature) & monitor the charge levels of the batteries.
There is an often reported bug with the combination that causes either random rebooting of the combo when sleeping or rapid battery drain - sometimes both together.
The fix for this is either to return to Asus - they have a mixed record of success in fixing it. Sometimes they swap out main boards - sometimes they don't and return the device as "no fault found"
A low tech solution to the problem revolves around doing two things...
1. Do not leave an SD card in the dock
2. Do not leave the combo together (ie docked) when not in use
Hope that helps. :)