From: ohland@charter.net   
      
   Rick, though I love posing possumbilities in obtuse waze, this battery   
   thing is past being deduced.   
      
   Let's put this on the back burner until we either have a battery pack   
   -OR- an actual 180W PSU so we could measure voltages and examine the   
   charging circuit.   
      
   Rick Ekblaw wrote:   
   > 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   
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