[Milsurplus] Running mobile on lead-acid batteries - WHY

[Hue Miller]

I haven't yet checked out all the replies on this, but i thank all who took 
time.
I should have spilled the game. I am thinking of the record of (supposed )
transmissions from Amelia Earhar's plane - AFTER the (supposed) 
crash-landing
somewhere, after her not finding the Howland airfield in July 1937.  This 
material
is well and interestingly described in the book "The Search for Amelia" just
recently published by the U.S. Naval Institute, book by R. Gillespie - same
person who will be leading an evidence seeking  expedition to Nikumaroro
( Gardner ) Island later this year.

I was trying to get a handle on how long her radio would hold up if running
solely on battery charge. The aircraft, Lockheed 10E, is similar to a Beech
18, twin engine, with a V type aerial with from front to twin tails. The 
ship
had 2 batteries; i assume simply paralleled for higher capacity. The 125 AH
figure i guesstimated from looking at WalMart at the biggest deep cycle
marine battery, which was 115 AH, and the biggest car battery, i think this
said 950 "cranking amps" - there was some other number in common, any-
way i guesstimated the AH for the car battery generously at 125 or so.
The radio was 100W input transmitter running at 12V in, suppressor 
modulated,
so there's no exact military equivalent i can think of, altho the BC-375 
seems
to pull about the same B+, approx. 1000 volts at mayb 150 mA. So i was
wondering how long transmissions could continue in a key-down manner,
continuous broadcast. The factors are the AH of the battery, the discharge
slope when about 50 amps are being drawn, and the point where the
transmitter power greatly declines or even stops due to low tube heater
emission.  ( The schematic of the Western Electric transmitter aboard
her plane is published in some 1930s text on "aircraft radio" - uncommon but
not rare. I think it may be in the book by "Morgan", author. )  I am 
guessing
the radio would quit about 8 volts, but that's a total guess. The tubes
in final if i recall were a pair of WE 212. ( Try to find those today. )  In 
this
little exercise, of course we can well understand there would have been no
concern with causing damage to the aircraft's batteries.
There was a matching WEco receiver, operated by control box also; this i 
would
dearly love to find.  Can't recall its type number offhand, type 12? Type 20 
?
Anyway the above exercise may seem a pointless effort but
apparently to some of us at least, an engrossing continuing mystery with at
least some chance of resolution.  ( The group doing the Niku expedition
and behind the book publication is "TIGHAR" - google will bring you their
website which has a number of articles resulting from their reseach. If you 
do
happen to check it out, i would appreciate your comments, direct mail to me. 
)
Well, that's about it.  -Hue Miller