KBT-2 out of radio battery charging

[Jack Brindle]

Now I have a question for the list regarding charging the K2 battery.  
I have the battery out of my K2 (while the KPA100 is installed), and  
I want to make sure the battery is charged. I have a Sears "1.5 Amp  
Fully Automatic Onboard Battery Charger Maintainer" that is designed  
to mount in a car well to keep a battery maintained when the car  
isn't driven for long periods of time. Should I use this with the  
GelCell in the KBT2, or should I find some other method?

I just want to make sure the battery doesn't die from not being  
charged so that next time I need it, it is ready to go.

Thanks!

-Jack Brindle, W6FB
=======================================================================


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[Don Wilhelm-3]

Jack,

I don't know the specs for that Sears charger, but many of those designed
for automotive batteries are nothing more than a cheap power supply.  A gel
cell can be maintained at a 'float voltage' level of about 13.8 volts at its
terminals and will do well - many security systems and small emergency
lighting systems use that method for the backup battery.

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.

73,
Don W3FPR

> -----Original Message-----
>
> Now I have a question for the list regarding charging the K2 battery.
> I have the battery out of my K2 (while the KPA100 is installed), and
> I want to make sure the battery is charged. I have a Sears "1.5 Amp
> Fully Automatic Onboard Battery Charger Maintainer" that is designed
> to mount in a car well to keep a battery maintained when the car
> isn't driven for long periods of time. Should I use this with the
> GelCell in the KBT2, or should I find some other method?
>
> I just want to make sure the battery doesn't die from not being
> charged so that next time I need it, it is ready to go.
>
> Thanks!
>
> -Jack Brindle, W6FB
> =======================================================================
>

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[Vic K2VCO]

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
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[Don Brown-4]

Hi

You could use one of my solar controller kits and a 15-18 volt wall wart or
power supply in place of the solar panel. You would just need a 5-10 ohm 10
watt resistor in series with the wall wart to limit the current and make the
supply simulate a constant current source like a solar panel. I still have a
few of the low current 1.5 amp versions left at $16 or the 16 amp version at
$30. For this application the low current version would be fine. This
controller is designed to keep a SLA battery charged and can be left
connected to the battery indefinitely

Don Brown




----- Original Message -----
From: "Jack Brindle" <[hidden email]>
To: "Elecraft List" <[hidden email]>
Sent: Wednesday, September 07, 2005 5:14 PM
Subject: [Elecraft] KBT-2 out of radio battery charging

> Now I have a question for the list regarding charging the K2 battery.
> I have the battery out of my K2 (while the KPA100 is installed), and
> I want to make sure the battery is charged. I have a Sears "1.5 Amp
> Fully Automatic Onboard Battery Charger Maintainer" that is designed
> to mount in a car well to keep a battery maintained when the car
> isn't driven for long periods of time. Should I use this with the
> GelCell in the KBT2, or should I find some other method?
>
> I just want to make sure the battery doesn't die from not being
> charged so that next time I need it, it is ready to go.
>
> Thanks!
>
> -Jack Brindle, W6FB
> =======================================================================
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

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[Don Wilhelm-3]

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
> --
>

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[Vic K2VCO]

W3FPR - Don Wilhelm wrote:

[re the A&A Engineering Smart Charger]
> 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.

Yes, you're absolutely correct -- it's the bulk current that's adjustable.

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Charles Greene-2]

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

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