[Elecraft] KX3 Battery charging

[Matt Zilmer]

Yes, 13.8VDC is required to charge.  The voltage drop has to be above
a certain value to properly regulate the charge voltage and current
level.

I had a set of 1750s that I put in the KX3 and charged.  They charged
faster than the nominal C/10 rate, but still charged up just fine.  I
think the 1900 mAH minimum is stated so that the charge rate is C/10
or less.  But lower capacity cells will also charge, just at a higher
rate.

I'm using a 9A variable switcher set to 13.9VDC output.  This PSU also
powers other loads.  It had to be "ferrited" half to death to kill the
switching harmonics.  :)

73,
matt W6NIA

On Mon, 08 Apr 2013 16:22:35 +0200, you wrote:

>And do not forget that the supplied voltage needs to be correct to 
>charge the cells.
>
>I use 2400 mAh cells (Sanyo Eneloop XX) without any problem.
>
>As stated in the KXBC3 manual:
>only NiMH cells rated at 1900 mAH or greater may be charged with the KXBC3.
>
>As far as I know the voltage applied should be more than 13.5 volts. 
>Using a standard lead-acid battery as a source will not work.
>
>However I have tried to lower the voltage while charging. At 13.8 Volt 
>the current drawn from my power supply is 330 mA. Initially I could sink 
>the voltage to  12.7 Volt keeping 330 mA. Under that voltage, current 
>dropped gradually and at 12.0 I got the "low supply" message on the KX3 
>display. While charging, the voltage needed to be increased at times to 
>maintain the 330 mA current flow and the "low supply" message showed at 
>12.5 volt, which proves that you cannot get a full charge on that 
>voltage level.
>
>The bottom line is: Use a power supply that can deliver at least 0.5 
>Amp. at 13.8 Volt as a "charge only" option.
>
>
>
>73,
>Peter - PA0PJE
>
>Op 2013-04-06 21:22 schreef Matt Zilmer:
>> Any capacity NiMH cells are OK.  They will charge at the rate of 200
>> mA.  Your 1900's should charge from 0SOC to fully charged in about ten
>> hours.
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