K2 Low Voltage Cutout

[k6dgw]

I, and a friend, purchased "12V 9.8Ah" Li-ion batteries.  Unfortunately,
all the specs plus everything on the battery is in Chinese, which more
unfortunately, the locals at the Sechuan Cuisine can't really decipher.
  Mike has moved on to an A123, probably a wise move, he hikes up big
mountains to put them on the air for SOTA.

I've discharged and charged this battery several times, and it really
appears to be a 7 or so Ah battery.  I know that the input voltage to my
K2 is regulated down to something quite a bit less, and it really
doesn't care what I feed it until it gets to some low point.  I'm taking
it to a SOTA activation at Leviathan Peak over Field Day.

The battery seems to have a more or less linear voltage vs discharge
curve.  Question:  At what voltage should I consider switching to an
alternate battery so my K2 doesn't die mid-Q?

Now, ALL ... this is a very specific question, the answer is a number,
in volts, that's all I'm looking for. This is not intended to start a
very long thread on battery chemistries, buying from China, better
batteries, how Elecraft could make the K2 better, interfacing a P3 with
my K2, KPA500 cables, ... and I really hope you get the idea.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
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[Phil Kane-2]

On 6/10/2011 9:02 PM, Fred Jensen wrote:

> Now, ALL ... this is a very specific question, the answer is a number,
> in volts, that's all I'm looking for.

I use 11.5 volts as the cut-off point to be safe. YMMV.

---
73 de K2ASP - Phil Kane
Elecraft K2/100   s/n 5402

>From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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[Dave KK7SS]

On 6/10/2011 9:02 PM, Fred Jensen wrote:

> Now, ALL ... this is a very specific question, the answer is a number,
> in volts, that's all I'm looking for.

The spec sheet on the K2 states the voltage range as being from 10V to 15V, so 11.0v would have a nice safety buffer built in.

The problem with using Li-ion batteries for SOTA operation is that their voltage and discharge rates are heavily dependant on ambient temperature.
The colder they get the quicker the voltage drops and their useful life is dramatically shortened,
And with summits.. the higher, the colder!!

Visit this page
http://www.ibt-power.com/Battery_packs/Li_Ion/Lithium_ion_tech.html
  and look at the second "Typical Discharge Graph"
and you'll see what I mean.

The standard discharge curves might also be of interest.

--
Dave G  KK7SS
 Richland, WA

'59 Morris Minor 1000
'65 Sprite - in process
'06 Honda Civic Hybrid
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[Mike Maloney]

Hi Fred, 
I would vote for 11.0 or possibly even 10.5 Vdc, if K2 specs say opr range is 10-15V.
Too bad you couldnt borrow an Astro Whattmeter from an RC plane or car enthusiast. With that you could actually measure the Ah demand of the K2 as well as get a good idea of the actual energy and operating time available from the battery.   
73, Mike  AC5P



--- On Fri, 6/10/11, Fred Jensen <[hidden email]> wrote:


From: Fred Jensen <[hidden email]>
Subject: [Elecraft] K2 Low Voltage Cutout
To: "Elecraft Reflector" <[hidden email]>
Date: Friday, June 10, 2011, 11:02 PM


I, and a friend, purchased "12V 9.8Ah" Li-ion batteries.  Unfortunately,
all the specs plus everything on the battery is in Chinese, which more
unfortunately, the locals at the Sechuan Cuisine can't really decipher.
  Mike has moved on to an A123, probably a wise move, he hikes up big
mountains to put them on the air for SOTA.

I've discharged and charged this battery several times, and it really
appears to be a 7 or so Ah battery.  I know that the input voltage to my
K2 is regulated down to something quite a bit less, and it really
doesn't care what I feed it until it gets to some low point.  I'm taking
it to a SOTA activation at Leviathan Peak over Field Day.

The battery seems to have a more or less linear voltage vs discharge
curve.  Question:  At what voltage should I consider switching to an
alternate battery so my K2 doesn't die mid-Q?

Now, ALL ... this is a very specific question, the answer is a number,
in volts, that's all I'm looking for. This is not intended to start a
very long thread on battery chemistries, buying from China, better
batteries, how Elecraft could make the K2 better, interfacing a P3 with
my K2, KPA500 cables, ... and I really hope you get the idea.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
______________________________________________________________
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