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In regard to the battery regulator charging voltage numbers, I’d like to
throw out something that has always bothered me.  A great deal of
engineering went into the seemingly simple mechanical regulator to
insure that it tracked the temperature/charge curve requirements of the
battery.  The spring used was actually bi-metallic in order to change
the voltage regulation point with temperature.  This in part is why it
is mounted near the battery in cars, so it can sense the ambient
temperature and compensate.  I am new to Lancairs as I’m currently in
the process of trying to acquire one, but in my Thorp T-18, the battery
was in the cabin, and the regulator on the firewall, totally at odds
with temperature sensing.  This scenario is reversed in a Bonanza I
recently had the occasion to fly in.  So, is this not a problem in the
Lancairs?  I guess the point I’m trying to make is that it is important
that the battery and regulator be co-located for temperature sensing
purposes, else that is another way to have charging problems.  For
interest’s sake, the voltage has to go up for colder.  From a service
clinic given by Motorola in 1957 the numbers given for the middle of the
normal specification range were:
15.4 V  @ 45 degrees F
14.2 V  @ 125 degrees F
13.6 V  @ 165 degrees F
So you can see that temperature can have a significant effect on the
ability of the battery to be charged and discussing setting it to tenths
won’t help unless it tracks and is co-located.

Charles R. Patton

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Please send your photos and drawings to marvkaye@olsusa.com.