"Sanjaya" wrote in message thlink.net...
Radio... Degen DE1102
Batteries charge in the radio via a procedure
described on p.3 of the English manual.
One selects a number of hours to charge
depending on the capacity of the batteries by
pressing the 1...9 number keys.
My problem... I don't know how to implement
this. The included rechargeables are 1100 mAh.
I want them fully charged, but don't want to
overcharge. And if I switch to my own 1800 mAh
batteries I'd want to charge them fully as well
without damage to the batteries or radio.

You would want to find out the various charge rates per key selected.
IE: 100ma, 500ma, etc...In general, a slow charge is rated as charging
with 1/10 battery capacity for current, for 15 hours. So if you had
the 1100 mah battery, you would want to charge at appx 110 ma, for 15
hours. The 1800, 180 ma for 15 hours. But the current used is not
critical. It will just vary the overall time it takes to get a full
charge. The best way to determine full charge is by watching the
voltage. If the batteries are nicads, you will see about 1.4 volts per
cell when you have a full "float charge". The normal resting voltage
with the charger unhooked will be about 1.2v per cell. So lets say you
have a battery
that is a total of 7.2 volts. "six 1.2v cells". When charging, the
voltage will gradually rise while charging. When fully charged, the
voltage will rise to appx 8.4 volts or so. The battery is fully
charged, and should be disconnected to avoid overheating. The nickle
hydrides are slightly different. The charge voltages are about the
same, but when they are fully charged, the voltage peaks, but then
slightly drops off a bit. This indicates full charge. This is why they
have separate chargers, or switchable ones that do both types for
nicads vs nickle hydride. A voltmeter is the best way to check charge,
and avoid overheating. But if you know the exact charge rates, you can
guestimate it and get pretty close. The battery will be warm when
fully charged. Thats one "caveman" method of estimation...:/ You have
to really start to overheat one before it will be damaged. You could
leave it a while extra, and it's not going to kill it. It's also
simple to build a charger that will limit current when the battery is
fully charged. Works about the same as a trickle car battery charger
that tapers off as it gets to full charge. I've built simple ones
using diodes.
What voltage battery is it? Probably 7.2, 9.6, or 12 volts. The
respective full float charge voltages would be appx 8.4, 11.2, or 14
volts. MK