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" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; <[email protected]>
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: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; <[email protected]>
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,
[EMAIL PROTECTED] 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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