My 3347 has been perfectly reliable.
I replaced the original power supply with one of the Belkin 12V DC-output UPS's that are meant for AT&T UVerse (»www.belkin.com/us/gatewaybattery ). Either the Rev. A or the Rev. B will work fine. These are expensive (around $130) new, but they can be found in used-merchandise venues (thrift stores, swapmeets, etc.) for a few dollars. If the battery is defective, this won't matter, but I would recommend disconnecting the defective battery (leave it installed in order to provide weight).