(ET) Battery Charging

[TVWAHL webtv net (THOMAS V WAHL)]

I just got the charger controller from Harry Landis and put it into an
aluminum box. I made it so that it is used outside of the tractor. The
tractor charger plugs into the controller and the controller connects to
AC. This is done with the solid state relay supplied. The disadvantage
to this is that the timer also cycles and must be readjusted
periodically to be "on" but maybe I will bypass it later. The controller
also has two wires to monitor the battery pack voltage. The controller
is a microcontroller meaning it is a small computer.

I did not change Harry's pot setting and recorded the following; When
the battery pack voltage falls to 38.8 volts the controller turns the
tractor charger on. When the voltage eventually reaches 43.6 volts the
controller turns the charger off. It takes some time for the pack
voltage to again fall to 38.8 volts causing the cycle to repeat. Thus
the cycle range is 4.8 volts for the pack (43.6-38.8). The measured
voltage  for each cell on average would then be  2.16 to 2.42 volts or
6.47 to 7.72 volts per battery.

There are no doubt other ways to attain this type of automatic control
but Harry has a device that appears to work well, is compact and
relatively simple, and apparently does what is needed to produce longest
battery life.