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nuckolls.bob(at)aeroelect
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 Posted: Fri Dec 10, 2010 5:54 am Post subject: Odyssey type batteries require a special type of charge |
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At 09:35 PM 12/9/2010, you wrote:
| Quote: |
<ftyoder(at)yoderbuilt.com>
What kind of Alternator do you get that produces 3 sequential charge
currents for the Odyssey?
Well, I thought it was funny.
Tim
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Exactly.
We considered launching into just such a protocol
for the next generation alternator regulator.
About 10 years ago I did a design study on a
microprocessor based regulator that would produce
a behavior not unlike the 'ideal SLVA battery
recharge curve'.
Having sized the task we then had to decide how
to merchandise the thing. It was going to be
about as expensive as an LR series regulator.
Further, since the marketplace was moving
decidedly toward the automotive alternators
with built in regulators, selection of my new
offering would demand other "inconveniences"
be embraced to modify the alternator for
external regulation.
What could I tell the customer about the value
for adding "the kitchen sink" to his suite of
system accessories? It was decided that the
economics of adding that expense to the cost
of ownership for an OBAM aircraft was not
justified. Selling the device would require
the kinds of advertising you encounter for
most other products and services . . . like
"new and improved".
The project was shelved.
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Fri Dec 10, 2010 6:08 am Post subject: Odyssey type batteries require a special type of charge |
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Actually most chargers will reduce the amount of current being fed to the
battery as the battery accepts charge. In effect as the battery accepts a
charge it becomes a large resistor to the current feeding it. The only
thing the three step charge does is lower the input requirements for the
charger.
The current demands on a constant voltage charger is
a function of what the battery is presently accepting at
that voltage. The only way the charger knows the battery
is charged is to monitor recharge current versus time. When
the recharge current has dropped below some target vale for
some minimum period of time, the smart charger switches to
the maintenance mode by dropping the output voltage to a
value just above the battery's open circuit voltage.
. . . just enough voltage to support the battery's internal
leakage losses but not enough to produce unwelcome charging.
Thus the battery is prevented from running itself down during
a long term maintenance interval.
This is why when you put a discharged battery on to charge it draws maximum
current and when the battery is close to full charged the current is
minimal. It is possible for chargers when they come to the end of a charge
cycle to increase the voltage fed to the battery causing the battery to boil
dry.
This IS the salient feature of the so-called "trickle"
chargers of yesteryear. They offer constant current
outputs that are not programmed to terminate when the
battery is charged. So even if the "trickle" is small,
say 100 mA, subjecting a battery to a month of small
but persistent "overcharge" is potentially terminal for
an SVLA battery.
Bob . . .
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Fri Dec 10, 2010 3:39 pm Post subject: Odyssey type batteries require a special type of charge |
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Thanks Bob...
Now I have to look up SVLA 
Noel
The current demands on a constant voltage charger is
a function of what the battery is presently accepting at
that voltage. The only way the charger knows the battery
is charged is to monitor recharge current versus time. When
the recharge current has dropped below some target vale for
some minimum period of time, the smart charger switches to
the maintenance mode by dropping the output voltage to a
value just above the battery's open circuit voltage.
. . . just enough voltage to support the battery's internal
leakage losses but not enough to produce unwelcome charging.
Thus the battery is prevented from running itself down during
a long term maintenance interval.
This IS the salient feature of the so-called "trickle"
chargers of yesteryear. They offer constant current
outputs that are not programmed to terminate when the
battery is charged. So even if the "trickle" is small,
say 100 mA, subjecting a battery to a month of small
but persistent "overcharge" is potentially terminal for
an SVLA battery.
Bob . . .
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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