(ET) Leaves and BB600 maintenance

[Chris Zach <cz alembic crystel com>]

Been doing leaves all day. When the tractor really slows down I noticed 
that turning off the deck and blower got me some more power to the main 
motor. So something is wrong with the battery pack.

Drove it till it was pretty much dead, then parked, put the blower and 
the deck on and started checking voltages on the BB600 cells. Most were 
at 1.0v (pretty low) however one cell in pack 1 was down to .4 volts 
under load, 2 in pack 2 were down to .4 and .6 volts, and one in the 
third pack was reading a solid 0.0v. Not good. So I turned off the 
blower+deck and checked voltages again. Aside from the dead cell in pack 
3, rest of cells came up to 1.1 or so volts.

Time to pull the bad cell. Put the rest of the pack on charge, checked 
the cell and it was at 2.00 volts to 3 volts. Bad. Pulled it out, took 
it to the shed, and on a lark hooked it up to a 1.5 volts power supply.

Sure enough it was pulling 2a no problem. Interesting. I then remembered 
one of the bolts was a bit loose, and the interconnects were pretty 
filthy. So I cleaned it up, cleaned up the bolt threads on the wire 
wheel, sprayed electronics cleaner into the bolt holes on the battery 
with a straw, cleaned up the nickel plated interconnects, and put it 
back in the battery. Now it reads a happy 1.4v under charge and after a 
drive was reading 1.0 under load at the end with the rest of them.

You can't kill these damn batteries. Well unless you overcharge them 
terribly with a bad E15 charger and a cap that takes the pack voltage to 
45v.

I then checked the other cells that were low: Pulled two of them, 
cleaned them up, cleaned the contacts, put them back in. Now they are 
reading better. I think I'll pull the last one that's reading low and 
clean it up as well.

So BB600's are nice, and do live for awhile, but the interconnects are a 
true pain: Tighten the stainless steel bolts too tight and they will 
break off. Not tight enough and the interconnects lose contact. But they 
do seem to last....

C