[Elecraft] KXBC3 charging

[Greg Troxel]

Mike Weir <ve3wdm at hotmail.com> writes:

> 1. Batteries that are installed are Ansmann 2850 MaH NiMH brand new
> min charge on them if any.
> 2. Put time on KX3 for 16 hours of charge time and left the Astron
> power supply for full 16 hours.

16h * 200mA = 3200 mAh.  That's not enough to fully charge 2850 mAh
batteries, but it's close enough that it doesn't explain what else you see.

> 3. In the morning after charge time tried to turn KX3 on with just
> battery power. It would not and found out needed to lower min voltage
> from 10v to 8.5v.

Did it indicate that the charge time completed successfully?  While you
may want lower BAT MIN, batteries coming off charge should be above 10V.

> 5. Took rig to the park this morning and it failed to start
> again. Double checked at home to make sure the new min volt setting
> saved and it did. I then moved the min
> setting to the lowest value which was 8.2 volts.

8.2V is 1.025 volts per cell.  This is pretty discharged, and that kind
of voltage is only reasonable under TX load.  If it's at that voltage on
receive, I don't expect TX to work.

> 6. On the display I am getting the following now PS. 13.6 volts (not
> sure way that as voltage on my Fluke meter at the Jack before it goes
> into the KX3 reads 13.8v)

That sounds ok, given the protection diode.

>     BT is reading 8.8v but is is fluctuating from 8.1v to 8.8v at times.
> Now even with an internal battery reading of 8.8 or a little less the
> rig should still turn on?? The only other thing I can think if is the
> 2850 MaH batteries need more than 16 hours of charge time?

You should see close to 11V after the batteries are charged, but not yet
used.  After light use, say 10 min of RX, no TX, they should still be
well above 10V, almost 11V (BT reading while there is external power, so
there isn't battery load).  A fully-charged NiMH resting voltage will be
about 1.3V (of course dropping under load).

So I would say that either one or more of your batteries is defective,
or they didn't really get charged.   Check to make sure they are all
installed the right way.

I'd recommend a refresh-analyze cycle in a Maha C9000 charger to qualify
the batteries before use, and annually or so to see if they are still
ok.  (I'd also recommend Maha/Powerex Imedion or Sanyo Eneloop, and to
avoid off-brand batteries.)

73 de n1dam