RJT> large quantities of automotive-type batteries also needs to
 RJT> consider the potential hazards involved with the fact that
 RJT> you're generating hydrogen gas during the charging process,
 RJT> which is more explosive than gasoline,
 BB> Yes, but I just learned something while this conversation is 
 BB> going on. If I am charging at a high rate and I want to break 
 BB> the circuit which is going to cause an arc, do it on a 
 BB> side-post battery rather than on a top post battery and you 
 BB> won't get an explosion. Top posts will explode, side posts 
 BB> won't. That may sound silly at first glance, but it makes 
 BB> sense. The gas is rising out of the battery and up into the 
 BB> atmosphere and if you break the circuit on a top post battery 
 BB> you are producing an arc right next to an open cell. If you 
 BB> break on a side post, it is below the level of the rising gas 
 BB> and much further away so it doesn't explode.
This whole procedure is a *LOT* more risky and trouble-prone than anything 
that *I* want to mess with.  I'll stick with charging situations which have 
transformers to isolate things,  and switches in the circuit which are far 
enough away from what's going on that I don't need to worry about it...
You may very well feel perfectly comfortable with what you're doing,  but I 
don't even care for the idea of doing things that way,  and am sure as heck 
not likely to mess around with it,  not when I've got alternatives.
Good luck!
--- 
---------------