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92 February 2008
I'm learning electronics on a self
study basis. My main book has a brief
section on impedance matching. The
key idea is that power transference will
be at a maximum when the source
impedance is equal to the load impedance. It doesn't do a very good job
demonstrating the math. I need a more
#2081 Mark Jungmeyer
I am converting a 1981 DeLorean
into an electric vehicle and I need
advice on building a battery charger for
my series string of 13, 12 volt Deka
9A31 AGM (sealed absorbed glass
mat) batteries which are 100 Ah each.
The manufacturer recommends a three
stage charge cycle:
First, start with a constant current
of 30 amps until the voltage of each
battery reaches 14. 4-14. 6 volts (187.2-
189.8 volts for the string).
Second, charge at a constant voltage of 14. 4-14. 6 volts (187.2-189.8
volts for the string) until "the current
acceptance drops by less then 0.10
amperes over a one hour period;" max
time 12 hours.
Third, maintain a constant terminal
voltage of 13. 5 volts (175.5 volts for
It would be best to have an option
to operate off 110 volts when 220 volts
is not available and to optionally limit
the supply current so as not to overload
a low capacity circuit breaker when
charging away from home.
Ideally, it would be better to charge
each battery separately so they are
properly balanced, but using 13 chargers seem a bit too bulky. Any ideas?
#2082 Dave Delman
I'm trying to interface a thermal
IBM PC Compact Printer (Model
5181001) to a micro and need the
Tech manual, or information describing
the timing, commands, and pinouts of
the printer. I’ve searched the Web, but
can't locate any info other than it was
used with IBM PC Jr. Plenty of these
printers are for sale, just no documentation that I can find.
Does this printer have the same
interface as another printer that I might
be able to locate?
I need a cheap — but reliable —
remote liquid level sensor setup for my
home heating fuel oil tank.
[#11074 - November 2007]
Is there a unit or circuit to