I finally got around to getting the printer working and trying out the battery. Then I fought IR for a while...
I had to baby that print head to finally get it to work. It took about 12hrs hot constant hot water + soap exposure to get it to stop releasing more ink.
Tranxit may be a proprietary IR interface and IrDA may be a more standardized version. This laptop is from '94 which I think predates IrDA.