I have a new product, a long time coming, for the Fanuc Serial Pulsecoders. It has only been tested with the encoders I have available right now, but should work with a variety of them. It converts the sort-of absolute position data from the encoder to quadrature with index. It also puts out the commutation (or Hall) signals for an 8-pole motor.
The ABS pulsecoder does not need a backup battery. Other encoders cannot provide commutation or index alignment info until they have passed the index mark, so it is best to provide a backup battery to the encoder.

See it at