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KBT2 charging question

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Mike Markowski

KBT2 charging question

The KBT2 manual says 14.0V +/- 0.2V is needed to charge the battery. Does that
mean something like an Astron putting out 13.8V is enough or is that too close
to the edge? I seem to recall someone saying it was not enough ideally but
can't find the note now...or maybe I'm remembering incorrectly!

Thanks for any info,
Mike ab3ap
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Don Wilhelm-3

RE: KBT2 charging question

Mike,

The 'float voltage' that must be applied to an SLA battery terminals should
be 13.8 volts to maintain a full charge on the battery. The K2 has a series
diode in the power supply line for reverse polarity protection - that diode
drops about .2 volts.

What that means is: to obtain 13.8 volts at the battery terminals, one must
connect a supply of 14.0 volts to the K2 to maintain full charge on the
battery.

There is an intenal pot in the Astron to adjust the output voltage, so it
may be a simple matter to increase the Astron voltage - locating the correct
pot may be more of a challenge, be certain you adjust the proper pot.

73,
Don W3FPR

> -----Original Message-----

>
> The KBT2 manual says 14.0V +/- 0.2V is needed to charge the
> battery. Does that
> mean something like an Astron putting out 13.8V is enough or is
> that too close
> to the edge? I seem to recall someone saying it was not enough
> ideally but
> can't find the note now...or maybe I'm remembering incorrectly!
>
> Thanks for any info,
> Mike ab3ap
>

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Fred (FL)

RE: KBT2 charging question

In reply to this post by Mike Markowski

Sounds like an Elecraft design glitch! Why would
one want to adjust their DC 13.8VDC Astron, to make
up for it? Circuit needs a mod.

Fred
N3CSY

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Don Wilhelm-3

RE: KBT2 charging question

Fred,

Not a design glitch IMHO - there is no way that Elecraft can redesign the
float voltage for an SLA battery!! plus:
I for one would not eliminate the series protective diode, so unless someone
comes up with a protective diode with zero voltage drop, we just have to
deal with those two parameters.

One can always just connect whatever power supply voltage that is available
and accept the results. The battery will have some level of charge with a
13.8 volt supply connected, but it will never come up to full capacity
charge.

73,
Don W3FPR

> -----Original Message-----
>
> Sounds like an Elecraft design glitch! Why would
> one want to adjust their DC 13.8VDC Astron, to make
> up for it? Circuit needs a mod.
>
> Fred
> N3CSY
>

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Mike Markowski

Re: KBT2 charging question

In reply to this post by Don Wilhelm-3

Thanks, Don & Tom, for your help. Now I'll scout around the web for the Astron
schematic and try to find that pot.

I'm still debating whether to build a K1 to bring along to places with me or to
build a fully kitted K2 QRP cover (ant. tuner and battery). The K2 cover is
cheaper, the K1 building is more fun.

73,
Mike ab3ap

Don Wilhelm wrote:

> Mike,
>
> The 'float voltage' that must be applied to an SLA battery terminals should
> be 13.8 volts to maintain a full charge on the battery. The K2 has a series
> diode in the power supply line for reverse polarity protection - that diode
> drops about .2 volts.
>
> What that means is: to obtain 13.8 volts at the battery terminals, one must
> connect a supply of 14.0 volts to the K2 to maintain full charge on the
> battery.
>
> There is an intenal pot in the Astron to adjust the output voltage, so it
> may be a simple matter to increase the Astron voltage - locating the correct
> pot may be more of a challenge, be certain you adjust the proper pot.
>
> 73,
> Don W3FPR

Earl W Cunningham

Re: KBT2 charging question

In reply to this post by Mike Markowski

Fred, N3CSY wrote:

"Sounds like an Elecraft design glitch! Why would one want to adjust
their DC 13.8VDC Astron, to make up for it? Circuit needs a mod."
==========
The diode in series with the power input to a radio is good design
technique. Without that protection, if you accidentally connect the
power with the wrong polarity, pop goes the radio!

73, de Earl, K6SE
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Ian Stirling, G4ICV, AB2GR

Re: KBT2 charging question

In reply to this post by Don Wilhelm-3

On Thursday 02 November 2006 09:55, Don Wilhelm wrote:

> There is an intenal pot in the Astron to adjust the output voltage, so it
> may be a simple matter to increase the Astron voltage - locating the correct
> pot may be more of a challenge, be certain you adjust the proper pot.

I have an Astron VS-35, ten dollars more than the RS-35,
and it has front panel adjustable voltage to 15 volts and
adjustable current limiting.

Ian, G4ICV, AB2GR, K2 #4962
--
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John Lonigro

Re: KBT2 charging question

In reply to this post by Don Wilhelm-3

Don et al:
I've never tried this, but I've been wondering if any protection would
be given the K2 if there were a reverse-biased diode running from the
+13.8V input to ground. Put a 5 amp fuse in the positive line between
the diode and the power socket and it should immediately blow if the
diode senses a reverse hookup. With a correct hookup, the K2 would get
the full voltage from the power supply. My guess is the K2 might still
experience some damage before the fuse blew, but I'm not smart enough to
know that for sure and I'm definitely NOT going to try it on mine! I
haven't noticed any problems with the series diode.

Just some food for discussion, but let's not have a food fight over it (hi).

73's,

John AA0VE

Don Wilhelm wrote:
> Fred,
>
> Not a design glitch IMHO - there is no way that Elecraft can redesign the
> float voltage for an SLA battery!! plus:
> I for one would not eliminate the series protective diode, so unless someone
> comes up with a protective diode with zero voltage drop, we just have to
> deal with those two parameters.
>
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Don Wilhelm-3

RE: KBT2 charging question

In reply to this post by Mike Markowski

Mike,

BAMA has Astron schematics, see if your supply is in the list there
http://bama.sbc.edu/astron.htm

The K2 will provide full band coverage as well as SSB, and double the power,
but it weighs more - the decision will have to be based on your wnats and
desires.

73,
Don W3FPR

> -----Original Message-----
>
> Thanks, Don & Tom, for your help. Now I'll scout around the web
> for the Astron
> schematic and try to find that pot.
>
> I'm still debating whether to build a K1 to bring along to places
> with me or to
> build a fully kitted K2 QRP cover (ant. tuner and battery). The
> K2 cover is
> cheaper, the K1 building is more fun.
>
> 73,
> Mike ab3ap
>

Don Wilhelm-3

RE: KBT2 charging question

In reply to this post by John Lonigro

John,

While that method is used in many instances, remember that 'the transistors
will always protect the fuse!'

I have seen (and created myself <G>) instances where that parallel diode
will open as soon as it sees a large current impulse due to the reversed
polarity (and before the fuse reacts) and the protection mechanism itself is
gone. The series diode is much safer for the equipment.

The K2 does have that type protection circuit (RF Board schematic D12) as
well as the series diode, D12 is after the self-resettable fuse, so if you
want to try it, all that is necessary is to bypass D10 with a bit of wire
(not on my K2 please) <G>

73,
Don W3FPR

> -----Original Message-----
>
> Don et al:
> I've never tried this, but I've been wondering if any protection would
> be given the K2 if there were a reverse-biased diode running from the
> +13.8V input to ground. Put a 5 amp fuse in the positive line between
> the diode and the power socket and it should immediately blow if the
> diode senses a reverse hookup. With a correct hookup, the K2 would get
> the full voltage from the power supply. My guess is the K2 might still
> experience some damage before the fuse blew, but I'm not smart enough to
> know that for sure and I'm definitely NOT going to try it on mine! I
> haven't noticed any problems with the series diode.
>
> Just some food for discussion, but let's not have a food fight
> over it (hi).
>
> 73's,
>
> John AA0VE
>

Tom McCulloch

Re: KBT2 charging question

In reply to this post by Don Wilhelm-3

I couldn't get thru to the BAMA site but found the schematics at
http://www.repeater-builder.com/astron/astron-index.html

I have the RS-35M, and wasn't aware of the 13.8 volts needed for full
charge, so I'll be \inside the Astron this weekend. (looks like R 104 on the
RS-35M)

Thanks for the info.

Tom
WB2QDG
K2 1103

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Mike Markowski" <[hidden email]>; <[hidden email]>
Sent: Thursday, November 02, 2006 5:37 PM
Subject: RE: [Elecraft] KBT2 charging question

> Mike,
>
> BAMA has Astron schematics, see if your supply is in the list there
> http://bama.sbc.edu/astron.htm
>
> The K2 will provide full band coverage as well as SSB, and double the
> power,
> but it weighs more - the decision will have to be based on your wnats and
> desires.
>
> 73,
> Don W3FPR
>
>> -----Original Message-----
>>
>> Thanks, Don & Tom, for your help. Now I'll scout around the web
>> for the Astron
>> schematic and try to find that pot.
>>
>> I'm still debating whether to build a K1 to bring along to places
>> with me or to
>> build a fully kitted K2 QRP cover (ant. tuner and battery). The
>> K2 cover is
>> cheaper, the K1 building is more fun.
>>
>> 73,
>> Mike ab3ap
>>
>
> _______________________________________________
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N2EY

Re: KBT2 charging question

In reply to this post by Mike Markowski

In a message dated 11/2/06 11:50:28 AM Eastern Standard Time,
[hidden email] writes:

> Sounds like an Elecraft design glitch!

It's not. It's actually a very good design.

Why would
>
> one want to adjust their DC 13.8VDC Astron, to make
> up for it?

Because it's what is needed.

Circuit needs a mod.
>
>
No!

Elecraft rigs are, above all else, QRP CW rigs. They are meant to be as
portable as possible, which is why the small size and provision for internal
battery.

The battery needs a certain voltage for charging. That's determined by the
type of battery used, and the power supply/charger must be adjusted to deal with
it, because the battery is not adjustable.

The blocking diode is a special low-drop part, to waste the minimum of power.
It serves two purposes:

1) to protect the rig from reverse-polarity applied to the power input jack,

2) To prevent discharging the internal battery into an external load.

In portable operation, and even at home, the diode prevents a lot of possible
problems. The design is very well thought out and needs no changes.

There's nothing magic about 13.8 volts, btw,

73 de Jim, N2EY
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Tom McCulloch

Re: KBT2 charging question

I want to make sure I'm following this. I

need to see 13.8 volts immediately after the protective diode. Is that
correct?

Thanks
Tom
WB2QDG
K2 1103

----- Original Message -----
From: <[hidden email]>
To: <[hidden email]>; <[hidden email]>
Sent: Thursday, November 02, 2006 10:22 PM
Subject: Re: [Elecraft] KBT2 charging question

> In a message dated 11/2/06 11:50:28 AM Eastern Standard Time,
> [hidden email] writes:
>
>
>> Sounds like an Elecraft design glitch!
>
> It's not. It's actually a very good design.
>
> Why would
>>
>> one want to adjust their DC 13.8VDC Astron, to make
>> up for it?
>
> Because it's what is needed.
>
> Circuit needs a mod.
>>
>>
> No!
>
> Elecraft rigs are, above all else, QRP CW rigs. They are meant to be as
> portable as possible, which is why the small size and provision for
> internal
> battery.
>
> The battery needs a certain voltage for charging. That's determined by the
> type of battery used, and the power supply/charger must be adjusted to
> deal with
> it, because the battery is not adjustable.
>
> The blocking diode is a special low-drop part, to waste the minimum of
> power.
> It serves two purposes:
>
> 1) to protect the rig from reverse-polarity applied to the power input
> jack,
>
> 2) To prevent discharging the internal battery into an external load.
>
> In portable operation, and even at home, the diode prevents a lot of
> possible
> problems. The design is very well thought out and needs no changes.
>
> There's nothing magic about 13.8 volts, btw,
>
> 73 de Jim, N2EY
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
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> Elecraft web page: http://www.elecraft.com

Douglas Todd

Re: KBT2 charging question

Take a look at the charging specifications from the datasheet:

http://www.powerfactorinc.com/Batteries/ps-1229.htm

It appears that the 100 - 200 mv drop across the shockey diode is
acceptable. This lowers the 13.8 volt output from the power supply to 13.6
to 13.7 volts. The float voltage can go as low as 13.5 volts across the
battery terminals.

Doug (KE7GYQ)

----- Original Message -----
From: "Tom McCulloch" <[hidden email]>
To: <[hidden email]>; <[hidden email]>
Sent: Thursday, November 02, 2006 8:26 PM
Subject: Re: [Elecraft] KBT2 charging question

>I want to make sure I'm following this. I
>
> need to see 13.8 volts immediately after the protective diode. Is that
> correct?
>
> Thanks
> Tom
> WB2QDG
> K2 1103
>
>
>
> ----- Original Message -----
> From: <[hidden email]>
> To: <[hidden email]>; <[hidden email]>
> Sent: Thursday, November 02, 2006 10:22 PM
> Subject: Re: [Elecraft] KBT2 charging question
>
>
>> In a message dated 11/2/06 11:50:28 AM Eastern Standard Time,
>> [hidden email] writes:
>>
>>
>>> Sounds like an Elecraft design glitch!
>>
>> It's not. It's actually a very good design.
>>
>> Why would
>>>
>>> one want to adjust their DC 13.8VDC Astron, to make
>>> up for it?
>>
>> Because it's what is needed.
>>
>> Circuit needs a mod.
>>>
>>>
>> No!
>>
>> Elecraft rigs are, above all else, QRP CW rigs. They are meant to be as
>> portable as possible, which is why the small size and provision for
>> internal
>> battery.
>>
>> The battery needs a certain voltage for charging. That's determined by
>> the
>> type of battery used, and the power supply/charger must be adjusted to
>> deal with
>> it, because the battery is not adjustable.
>>
>> The blocking diode is a special low-drop part, to waste the minimum of
>> power.
>> It serves two purposes:
>>
>> 1) to protect the rig from reverse-polarity applied to the power input
>> jack,
>>
>> 2) To prevent discharging the internal battery into an external load.
>>
>> In portable operation, and even at home, the diode prevents a lot of
>> possible
>> problems. The design is very well thought out and needs no changes.
>>
>> There's nothing magic about 13.8 volts, btw,
>>
>> 73 de Jim, N2EY
>> _______________________________________________
>> 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

RE: KBT2 charging question

In reply to this post by Tom McCulloch

Tom,

Correct - That is usually the goal - BUT, if one wants to get 'picky' about
the real voltage required, that will depend on the temperature, state of
charge in the battery, the particular battery characteristics, and a whole
lot of other variables, specified or not.

So, the 13.8 volts can be regarded as a workable average - the actual
requirement for a particular battery will vary with the particular
circumstance - which gives rise to a +/- 0.2 (or 0.3) volt variation that is
sometimes mentioned. One battery could require 13.6 volts while another
could require 14.0. Sorry about any confusion, but such are the facts -
every rule has an exception that might apply in some cases, one could go
nuts trying to get everything exactly right, but with so many variables,
reality (and sensibility) force us to deal with average conditions unless we
have other specific details in hand.

73,
Don W3FPR

> -----Original Message-----
>
> I want to make sure I'm following this. I
>
> need to see 13.8 volts immediately after the protective diode. Is that
> correct?
>
> Thanks
> Tom
> WB2QDG
> K2 1103
> Checked by AVG Free Edition.
> Version: 7.1.409 / Virus Database: 268.13.23/513 - Release Date: 11/2/2006
>
>

Don Wilhelm-3

RE: KBT2 charging question

In reply to this post by Douglas Todd

Doug,

I finally looked at your reference, and find that your quoted voltage is
only a portion of the charging spec. While a float voltage at 13.6 to 13.7
volts is OK, it will not fully charge the battery until applied for a very
long time (many tens of hours, maybe even hundreds of hours).

Notice the 'float voltage' you quoted is only the last part of the
recommended charging cycle:
1) charge with a constant current of 580 ma until the terminal voltage
reaches 14.4 to 14.7 volts.
then 2) Hold the terminal voltage at 14.4 to 14.7 volts until the current
drops to 29 ma.
3) After that, stop charging or hold the float voltage at 13.5 to 13.8
volts.

The KBT2 uses a series resistor to limit current, and the series diode
voltage drop must be considered too. The KBT2 instructions correctly state
that a voltage of 14.0 volts is recommended.

For those who want to fully charge the internal battery and maintain that
condition properly, I refer you to the SmartCharger article on my website
http://w3fpr.qrpradio.com which shows how I connected an external 3 state
charger to my internal battery (fused for safety). I operate my QRP K2 from
the battery at all times (no other power source connected) and the 3 state
charger keeps the battery topped off. One could use a solar panel
controller to charge the battery in place of the AC powered SmartCharger
that I used - I am thinking of adding a solar controller here.

73,
Don w3FPR

> -----Original Message-----
> Take a look at the charging specifications from the datasheet:
>
> http://www.powerfactorinc.com/Batteries/ps-1229.htm
>
> It appears that the 100 - 200 mv drop across the shockey diode is
> acceptable. This lowers the 13.8 volt output from the power
> supply to 13.6
> to 13.7 volts. The float voltage can go as low as 13.5 volts across the
> battery terminals.
>
> Doug (KE7GYQ)
>