XPost: alt.home.repair, sci.electronics.repair   
   From: occassionally-confused@nospam.co.uk   
      
    wrote:   
   >> I always did positive first.   I will switch!   
   >   
   >    Think it out  first  -   then decide.   
      
   I'm thinking... I'm thinking... I'm trying to think this thing out.   
   I don't think it matters all that much which cable goes first or last.   
      
   As far as I can think about it, the last connection is the one that sparks.   
   And that means the first disconnection is the one that sparks.   
      
   Since you don't want that spark to be near any concentration of flammable   
   hydrogen gas, I guess the theory that I'll concoct is you want the negative   
   cable to be as far from that hydrogen gas as possible.   
      
   That makes it the negative cable to be the last to connect.   
   And the first to disconnect.   
      
   Now, if the theory is to proceed accordingly, we have to decide which   
   battery has the most chance of having excess hydrogen gas.   
      
   The answer likely is neither will have any, but if we have to choose, which   
   battery will have more hydrogen outgassing?   
      
   (A) The donor battery (which is likely already topped off)  or   
   (B) The recipient battery (which is likely taking the greater charge)   
      
   The answer seems, to me, to be neither battery will have excess hydrogen   
   gas, but if I was forced to choose, I guess the battery being charged the   
   most has the most excess hydrogen gas, which would clearly be the donor.   
      
   All this is just "thinking it out" so tell me if I'm wrong so I learn from   
   your expertise (the royal your that is, as everyone has something to say).   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)