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From: Kenneth Cooperstein <cprstn54_at_att.net>
subject: [Paddlewise] HX460S and external battery packs
Date: Wed, 16 Oct 2002 08:41:13 -0400
A while back I posted a message stating that the HX460S will drain an
external 7.2 volt NiMH pack before drawing on its internal Li-Ion
battery.  This desirable result was based on info from Standard that
over 6 volts at the power jack will run the radio but under 9 will not
trickle charge the Li-Ion battery.

Well, it turns out to be a little more complicated than that.  In my
test, the radio scanned and did RX for 48 hours before dieing.  From
time to time, I opened the external supply circuit and observed that the
radio immediately died -- suggesting that the Li-Ion battery would not
come on line when the voltage dropped at the external jack.  However, at
the end of the test, both batteries were flat.

It appears that an external pack that runs low (as opposed to open
circuit) *will* cause the internal Li-Ion to power the radio (or try to
charge the external pack).  At what point and why the internal battery
kicks in as a 7.2 volt external pack runs down is not yet known. 
Standard is looking into it.

I am trying the same experiment right now with an external 10-AA NiMH
pack (12V).  After 24 hours, it is evident from the LED that the
external pack is powering the radio and trickle charging the Li-Ion
battery -- as would be expected.

I am hoping -- but not confident -- that putting a diode on one of the
external pack leads will give the desired result: The radio runs off the
external pack and dies when the pack runs out, regardless of the state
of the Li-Ion battery.  Right now, the only way to assure this result is
to remove the Li-Ion battery while the external pack is plugged in.

Ken C
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