From: ekblaw@vnet.ibm.com   
      
   Louis Ohland wrote:   
   > Rick, the simplest [and slowest!] rate is c/1, a lot SIMMpler control   
   > circuit and it makes the least heat. I've seen c/5 mentioned, much   
   > shorter time, but more heat and it slaps the battery pack like the   
   > naughty boy it is.   
   >   
   > So... if you got to SEE the battery charging circuit, could you   
   > guesstimate capacity?   
   >   
   > The pittances we have of 26v and 40mA could mean whatever you wandt.   
   > Measuring the output connector in the battery well -MIGHT- tell us the   
   > actual charging voltage, which could be less than 26v. Maybe the charger   
   > input is 26v at 40mA?   
      
   OK, let's go back for another round of the guessing game.  If IBM did   
   not go for custom-built NiCD cells, you have a few common cell sizes to   
   choose from:  C size, sub-C size, AA size, AAA size, VARTA size pucks (3   
   cells stacked that are roughly a dime diameter, a bit less than an inch   
   long), the individual pucks used in the VARTA batteries that can stacked   
   to whatever length you desire in series, and then a handful of odd sizes   
   that largely never caught on.  Given that the battery pack must fit   
   within a 9.25" x 1.75" x 1.875" space, if the AA size was used, they   
   could be in a 3x3x4 configuration and the wiring would likely be 3x4 in   
   series, 3 stacks of 3x4 in parallel, giving you a nominal pack voltage   
   of 14.4V.  Each cell would likely be 600mAh meaning the pack would be   
   21.6 Wh.   
      
   If sub-C cells were used instead of AA, the configuration would likely   
   be 2x2x4 and the pack voltage would be either 9.6V or 19.2V depending on   
   whether you wired it as 2 parallel 2x4 or every cell serial.  Neither of   
   those choices seems likely, so I suspect the pack used AA sized cells.   
      
   Knowing that the pack has a 3 wire connection suggests positive,   
   negative and sense wires (most likely).  It could also mean one negative   
   and 2 positive if the sub-C cells were used and the pack was providing   
   two 9.6V outputs.   
      
   You could also get into some wonky possibilities if the battery backup   
   was ONLY providing 5V DC power, letting the hard drive "slide" for that   
   10 or 11 second period of backup power, but thinking about that makes my   
   brain hurt.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)