[Elecraft] KBT-2 out of radio battery charging

[Charles Greene]

GM,

Powersonic sells automatic chargers for SLA batteries that do just what you 
described, Don,  The PSC 12500A is the right charger for the KBT-2.  That's 
the 0.5 amp charger.  I keep my KBT-2 on float/charge with the PSC 12500A 
with the battery switch off unless I am on battery power, and it seems as 
good as new.  It was purchased with my K2 S/N 462 in 1999.  It has two 
lights; both light when it is in the stage 1 or 2 modes, and a single light 
stays on when it is in the stage three mode.

73,  Chas

At 11:36 PM 9/7/2005, W3FPR - Don Wilhelm wrote:
>Vic,
>
>Thanks for adding that - in my haste, I forgot to say that indeed for a
>Smartcharger, the current must be set with consideration for the battery.
>OTOH, I believe the thing that is usually adjusted is the 'bulk current'
>which is the high current part of the 3 stage charging cycle.
>
>Reviewing the UC3906 3 stage controller chip, I found that Stage 1 was the
>bulk current stage - where the resistance can be changed to limit the
>maximum current.  When the terminal voltage reaches 95% (13.7v) of the full
>charge voltage, stage 2 is triggered which increases the voltage (to 14.4
>volts for a 12 volt SLA), and the charging continues until the current drops
>to a small value - then stage 3 begins which limits the voltage to 13.8
>volts (trickle charge value).
>
>
>73,
>Don W3FPR
>
> > -----Original Message-----
> >
> > W3FPR - Don Wilhelm wrote:
> >
> > > Of course, an even better system is to use a 3 stage charge controller
> > > specifically designed for SLA batteries - something like the A & A
> > > Smartcharger would do a fantastic job.
> >
> > Keep in mind that the Smartcharger (and most likely other 3-stage
> > chargers) has an adjustment for the amount of trickle current.  If the
> > charger is designed for an automobile battery this will be too much for
> > a small gel cell and will destroy it.
> >
> > How do I know?  Because I have a Smartcharger and I made an error in
> > arithmetic when I selected the value of the resistor that controls the
> > trickle current, and the rest -- including my 4ah gel cell -- was history.
> >
> > --
> > 73,
> > Vic, K2VCO
> > Fresno CA
> > http://www.qsl.net/k2vco