Subject:
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Continuous charging
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 16 Jan 1999 18:52:21 GMT
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Original-From:
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Will Bain <willbain@cs.umt.edu=stopspam=>
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Viewed:
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922 times
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Graham, J. Todd wrote:
<snip>
> Also, I guess no one had an answer on the earlier question of running the HB
> in a continuous-power mode (ie from a wall-wart).
If you use zap charge mode, you'll end up cooking your batteries unless
the HB draws just the right amount of current. If you use any motors or
other high current devices connected to the HB, trickle charge mode will
not supply enough current to charge the batteries, and may cause the
wall-wart to overheat after the batteries are drained.
Perhaps you could instead simply replace the battery pack with a DC
power source, regulated just enough to keep the HB voltage within
acceptable bounds across its current draw range. A wall-wart will
probably not suffice, since the voltage would probably vary too much
(high or low) depending on current draw. (Note: wall-warts also seem
to waste a lot of energy in the form of heat, so unplug them when
they're not being used.) Although it would be overkill, a power supply
from an old PC would do the trick; I've seen ones that have various
regulated voltage taps from which to choose.
The other alternative is to whump up a smart battery charger that kicks
in when the battery voltage falls below a threshold. The safe way to
quickly recharge NiCd batteries is to ramp up the voltage supply until
the current into the batteries is somewhere in the neighborhood of
[battery capacity] / [a couple hours], but you must cease charging when
the voltage across them stops increasing. Beyond this point, the
batteries will generate heat which will destroy 'em pretty quickly.
Given how toxic and expensive they are, we should strive to keep NiCads
alive as long as possible. Another (less reliable) method of charging
would cut out when a temperature sensor (glued to a battery cell with
thermal glue, perhaps) reaches a threshold. Still, charging batteries
while the HB is drawing current will require a more sophisticated
charger than would be needed for simply charging batteries on their
own. Hope this helps. Best of luck to you!
--Will
, ,
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Wendy Parson, Americans detest all lies except
Will Bain, lies spoken in public or printed lies.
& Tatoosh --Ed Howe
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