[Kenwood] thg71a charging question

[Emil E. Hrivnak]

I disagree with some things in your 1st paragraph. If the charge rate is 
limited or controlled by a charging circuit internal to the radio, as most 
are, then whether you use a 500 ma. power supply or a 50 amp power supply 
makes no difference. The battery will only draw what the charge controller, 
in the radio, is set for.

Also an external charger has no knowledge of the battery voltage or 
temperature as you implied. Voltage level and temperature may be sensed by 
the internal charge controller and control the rate.

If the radio uses the same power input jack for charging as well as 
operating, then as long as the external supply can provide enough current 
to charge the battery and power the radio, and has a low enough ripple to 
not cause hum, there is no problem in using a big supply (not the little 
charger that comes with the radio), and charging and operating at the same 
time. Have done it for years.

Emil
N3EH


At 11:34 AM 12/07/2002, you wrote:
>Roy,
>
>It is not a good idea to use a bench power supply to charge ni-cad
>batteries.  Most chargers that come with a radio are designed to control
>both the voltage and the current based upon the internal impedance
>and/or temperature of the battery.  If the individual cells are not
>designed for rapid charging, you should not try to speed up the
>process.  Cells that can handle a three-hour charging cycle are designed
>to absorb the gases generated, and they can handle the higher
>temperatures.  If a rapid-charge battery pack is not available for your
>radio, you might be able to use NiMH cells in your dry cell holder.  Of
>course, you'll need a separate charger that is designed for NiMH cells.
>
>Re your other question, you should not have the radio turned on while
>charging the battery.  To do so diverts some charging current to run the
>radio, lengthening the time it takes to fully charge the battery.  Some
>radios draw enough standby current that the battery will never charge if
>the radio is turned on.  Since the charging current does not need to be
>filtered much, the ripple will modulate the carrier if the radio is
>keyed while in the charging stand- a big no-no!
>
>73, Eric Lemmon WB6FLY