[Elecraft] Re: Dead Battery

[Jeff Burns]

I am following up on my dead battery situation. I think what I have learned
may be helpful.

My battery most certainly failed from over-charging. I had originally
adjusted my voltage regulator using the K2 internal voltmeter taking account
of the drop across the diode. This method makes the assumption that the
power supply voltage is well regulated. Mine apparently is not.

When I measured the voltage at the battery terminals with the K2 off and no
battery connected the voltage was 14.15V.

I readjusted my regulator to give 13.8V at the battery terminals with the K2
off. When the K2 is turned on the voltage drops to 13.48V. If the K2 was
always on, the battery would now be undercharged, but since it spends most
of its time off it should be OK.

The old battery and my replacement are both made by Sentry Battery Corp, and
sold through Midstate Battery. It only cost $14.60 + shipping. The
specification is identical to the Power Sonic battery. It is possible that
this battery contributed to the short life, but for the price I decided to
give the brand a second chance.

Jeff Burns

AD9T

----- Original Message -----
From: "Jeff Burns" <jhburns@attglobal.net>
To: "elecraft_list" <elecraft@mailman.qth.net>
Sent: Sunday, June 30, 2002 22:46 PM
Subject: Dead Battery


> This year I started field day of running my K2 from the internal battery.
> Since the club was 5A I cranked the power up to 15w. Within a few minuets
I
> had a strange modulation of my side tone. The two-meter station even heard
> me, and I was on 15m CW. It took me an hour to figure out that the battery
> voltage was dropping below 8v causing the radio to reset with each dit and
> da. This was a surprise because the battery is less than a year old and is
> left on float charge all the time. Switching to an external battery fixed
> the problem.
>
> When I got home I charged the battery and measured the charge voltage at
the
> battery terminals. When the charger was first connected the voltage was
> 13.04V. After a day of charging it was at 13.89V. That looked good to me,
> but the battery will not hold a charge. If I leave it unplugged for a few
> hours it does the same thing it did on FD. Looks like I have a bad
battery.
>
> Now my question is what caused this battery to fail in less than a year?
The
> battery was purchased from a battery supply house I found on the Internet,
> rather than Elecraft. For a charger I use a laptop computer supply rated
19v
> and 2.64A (only cost $3). I made a box with a LM350AT voltage regulator to
> drop the 19v to 14v. Anything wrong with this setup?
>
> A higher amperage supply would be nice so I could run the K2 at full power
> with out the battery. I have also been tempted by the MFJ Miniature
> Switching Power Supply because of it would not need the voltage reducer.
Any
> thoughts?
>
> I will order a new battery in a few days, but do not want to have it
suffer
> the same fate as the last on.
>
> Jeff Burns
>
> AD9T
>
>