Hi again Roy
On (02 Nov 96) Roy J. Tellason wrote to Alec Cameron...
 AC> Maybe you remember the old Tungar chargers- these were a 1/2 
 AC> wave setup, a glass tube mercury diode the size of a 150 watt
 AC> lamp having a plate lead at top and a GES base 
 RJ> The unit I remember my grandfather having didn't seem to be a whole lot
 RJ> larger than a pretty standard light bulb,  maybe it wasn't that heavy a
 RJ> current charger.
When I say 150 watt I refer to today's compact size, roughly 6cm dia and 14 
m
high. My foot rule has been borrowed!
 AC> For that reason, some large batteries are provided with "end
 AC> cells". The charger floats across [say] 55 cells but the load 
 AC> is connected across only 50 of these. When an emergency arises 
 AC> and the battery volts fall after [say] 15 minutes loading, a 
 AC> contactor would automatically switch in the rested 5 end cells. 
 AC> Presto! 110 volts at the loads isntead of maybe 125 immediately 
 AC> at the start of the emergency.
 RJ> Hmm.
Last weekend I spoke with another ex- Utility employee, he reminded me of the
"counter- emf cells" sometimes used. Similar idea, but during the initial
period of emergency lighting, these end cells would depress the load volts
and receive a small charge via the load current and later these same cells
could be reversed to boost the falling voltage at the load. Fancy switching!
This is 1950s technology.  Cheers...ALEC
... FLASH! Energiser bunny arrested, charged with battery.
--- PPoint 1.92
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