🚀 go-pugleaf

From my previous post (Pseudo-static RAM Summary) you may know that I'm looking
into building a high capacity RAM Disk. While it is expensive (about $108/meg)
by my figuring's I can get a whopping 21+ Mbytes/sec transfer rate. With this
kind of performance it's worth taking a crack at it.

To do this however I need a power source. I'd like to use Radio Shack (RS)
High capacity NiCad batteries. The D size battery has a huge 4.3AHr capacity
at 1.25V! From what I read in previous messages this capacity is valid and
has been tested by Consumer Reports or somesuch.

I want to know a little more about how to feed these puppies. All I know I've
read from an article in Circuit Cellar Ink (July-August 1992) on Data Logger
construction. It has all kinds of battery and low-power goodies. Here's the
scoop I gathered (please feel free to amend or correct):

1. Standard NiCads can be charged at 1/10 of rated capacity (.1C). 
2. When charged at .1C it takes about 14 hours to charge to capacity.
3. Cells cannot be overcharged at .1C rate. The article implied that charging 
   power can be applied to the cells indefintely at this rate without damaging
   the cells.
4. Faster charging rates can be used to quick charge but special circuitry
   to detect temp. is necessary to shut off the charging process.

Are these correct?

The circuitry shown in the article described a very, very simple circuit:

Wall wart -> Limiting resistor -> Diode -> Battery -> Diode -> Chips

Is it that simple? The diodes were germanuim (sp) to ensure a low voltage drop
across them.

Any other suggestions or tips?

The article also described "float voltage". It seemd to be high than the rated
battery voltage. Why is that?

Lastly can anyone suggest a low power voltage regulator that requires low
voltage overhead? Something suitable for battery powered operations?

I'd like to keep a wall wart plugged into the batteries all the time even
though my off the cuff calculations indicate that I can get up to 18 weeks 
of usage from a single charge.

Thanks for any help you can give.

BAJ
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Another random extraction from the mental bit stream of...
Byron A. Jeff - PhD student operating in parallel!
Georgia Tech, Atlanta GA 30332   Internet: byron@cc.gatech.edu