http://evdl.org/docs/bb600_nicd.pdf Christopher Zach may have some thoughts. He's used BB600s for years.
Yep, that's the official doc.
That said, I'd be inclined to do more for their care than Christopher did. I'd probably spring for a modern charger with a true NiCd profile. I might add a DC:DC converter or two to run the lights and/or lift, so as to avoid imbalancing the battery. However, Christoper seems to have had pretty good results with the old GE boat anchor and battery taps. I expect he'll chime in with more info.
I'd agree, my "run it as is" works, but one should be able to get better capacity and such from a real charger. One of the key elements is these batteries like a *lot* of current on charge, and the on-board charger is kind of limited to a thousand watts or so. A charger that could do 1500 watts would be a lot better, and a real NiCD one that handles the batteries using the proper profile would be really good.
Putting more cells in parallel just reduces the charge current to each cell string. So buy the biggest charger you can.
In terms of voltages, the high charge voltage should be 1.54vpc or 46 volts. The E20 charger really can't get the pack above 42v at most, so there will be some lost capacity. I used to get around 20ah of use per string.
Leaving all the strings tied together is a "eh, it works" idea. A better solution would be to put a contactor on each string, with the first string always connected with a contactor that would "open" it if energized. That way you could tie the other contactors to the key switch signal, bonding all the strings only when driving (also let the charger do that as well for charging). Then you don't have to worry as much about self discharge of the strings into each other.
I don't really use taps anymore: I wire the lifts to run straight off 36 volts on front and rear. Use a real quality lift switch and a 15-20 amp fuse to protect the lift if it locks up and you should be happy with the attachments hopping like frogs in a dynamite pond. Likewise for lights just get a 36 to 12 volt inverter that's on when the lights are on and you will be in business.
the brake works in parking brake mode, but doesn't seem to do much otherwise. I have the manual, and am going to attempt to adjust the crown nut as described
Adjust the nut, clean up the brake, all that. It's a heavy tractor and if you're mowing up and down hills you can use the brake a lot.
Also make sure the pivot is in good shape on the brake pedal. You really don't want it to bind. Getting it out is a pain, but once out you can properly clean and lube it, then put in a washer on the pivot shaft to keep the pedal from binding.
C