If Research in Motion’s BlackBerry PlayBook is to succeed at market the way the company hopes, there are a few engineering hurdles to overcome. The most significant, according to Kaufman Bros. analyst Shaw Wu, is the device’s relatively poor battery life.

Sources tell him the tablet currently lasts just a few hours per charge, compared with rivals like Samsung’s Galaxy Tab, which lasts about six, and the iPad, which lasts upward of 10. If true, that’s an untenable situation for RIM, which really needs to hit the mark with the PlayBook, and it may cause a delay of the launch–if only for a bit.

“From our understanding, this 1 8 is 3 8 likely why RIMM pushed out its launch to the May 2011 quarter,” Wu writes. “Keep in mind that QNX (the OS on which PlayBook runs) wasn’t originally designed for mobile environments but rather for devices like network equipment and automobiles where battery life isn’t as much a constraint.”

In other words, as promising as plugging QNX into a tablet form factor with a dual-core processor and a gig of RAM sounds, it’s proving to be a bit of a challenge. So what’s the solution? Most likely a bigger battery. But obviously that will add to the heft of the device and perhaps require a design concession or two.

Given that, Wu takes a conservative view of PlayBook’s prospects; He figures RIM will sell 700,000 units in 2011, far less than the 1 million to 8 million that other analysts have been calling for. “As we have said before, we are not convinced that tablets outside of the iPad will see high volume success,” he concludes.