A friend and I both have G3 Pismos. His apparently discharged completely, or thats what we thought. (A mutual friend of ours said that if the Powerbook ever completely discharged, you needed a good battery to "jump start" the charging system. Apparently this is erroneous.)
In any case, I brought his powerbook home, stuck my battery into it, plugged in the power connector, and tried to fire it up. No good. Took the (dead) battery from his and put it in mine, and it came right up.