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K2 qrp battery drain estimation

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RobertG

K2 qrp battery drain estimation

If I'm operating a K2 at 5w cw, in S&P contest mode, I compute the
current drain under the stated conditions as follows:

conditions:
50% listening, 50% transmitting
CW 50% duty cycle

current:
200ma receive, more or less
1.0a transmit, more or less

current draw per hour:
100ma [30min rcv] + 250ma [30min xmit @ 50% duty cycle] = 350ma per hour

10Hr requires a 3.5Ahr battery
20Hr requires a 7.5Ahr battery
etc...

Is this more or less accurate, or have I missed something? Thanks.

...robert
--
Robert G Strickland, PhD ABPH - KE2WY
[hidden email]
Syracuse, New York, USA
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daleputnam

Re: K2 qrp battery drain estimation

Hi Robert,
The percentages that you use would be accurate for a casual contester, one that would do slow scan S&P...
If, on the other hand, you are trying to beat the record, and are intent on making the 10 ten box, the percentages
would be more accurate at 80% tx and 20 % rx. and remember that a battery drops voltage when it get close to discharge.
Will look for you /p during the next 'test, or FD.

Have a great day,

--... ...--
Dale - WC7S in Wy

> Date: Fri, 14 Jun 2013 22:28:10 +0000
> From: [hidden email]
> To: [hidden email]
> Subject: [Elecraft] K2 qrp battery drain estimation
>
> If I'm operating a K2 at 5w cw, in S&P contest mode, I compute the
> current drain under the stated conditions as follows:
>
> conditions:
> 50% listening, 50% transmitting
> CW 50% duty cycle
>
> current:
> 200ma receive, more or less
> 1.0a transmit, more or less
>
> current draw per hour:
> 100ma [30min rcv] + 250ma [30min xmit @ 50% duty cycle] = 350ma per hour
>
> 10Hr requires a 3.5Ahr battery
> 20Hr requires a 7.5Ahr battery
> etc...
>
> Is this more or less accurate, or have I missed something? Thanks.
>
> ...robert
> --
> Robert G Strickland, PhD ABPH - KE2WY
> [hidden email]
> Syracuse, New York, USA
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

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Bruce Beford-2

Re: K2 qrp battery drain estimation

In reply to this post by RobertG

> Is this more or less accurate, or have I missed something? Thanks.

You missed the fact that you really can't/shouldn't try to discharge the
full capacity of the battery. The life span of SLA batteries for instance,
are greatly reduced if you routinely go to greater than 50% depth of
discharge.
73
bruce
N1RX

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ny4g

Re: K2 qrp battery drain estimation

Bruce is right. QST had an article last month for a programmable LED to monitor battery voltage. It is easy to make. You should monitor the resting voltage to provide some margin from over discharging

Ariel NY4G

Sent from my iPhone

On Jun 14, 2013, at 7:17 PM, "Bruce Beford" <[hidden email]> wrote:

>> Is this more or less accurate, or have I missed something? Thanks.
>
> You missed the fact that you really can't/shouldn't try to discharge the
> full capacity of the battery. The life span of SLA batteries for instance,
> are greatly reduced if you routinely go to greater than 50% depth of
> discharge.
> 73
> bruce
> N1RX
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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Don Wilhelm-4

Re: K2 qrp battery drain estimation

In reply to this post by RobertG

Robert,

You are assuming you can draw the full rated Ahr from a battery - that
is not a good assumption, go with closer to half that amount of energy.
You will not be able to completely discharge the battery.

Secondly, your transmit current at 5 watts is a bit low, it will
generally be closer to the 1.4 to 1.9 Amp range (I just measured a K2
with T4 wound for "high efficiency at 5 watts" and it was drawing 1.2
amps with a 13.8 volt supply). Remember that the K2 tries to maintain
the requested power output, so as the battery voltage drops, the current
must increase to maintain the same power output. If the overall transmit
efficiency is 30% (you have to run the entire transmit chain, not just
the PA), you will have to put 15 watts in to get 5 watts output.

73,
Don W3FPR

On 6/14/2013 6:28 PM, Robert G Strickland wrote:

> If I'm operating a K2 at 5w cw, in S&P contest mode, I compute the
> current drain under the stated conditions as follows:
>
> conditions:
> 50% listening, 50% transmitting
> CW 50% duty cycle
>
> current:
> 200ma receive, more or less
> 1.0a transmit, more or less
>
> current draw per hour:
> 100ma [30min rcv] + 250ma [30min xmit @ 50% duty cycle] = 350ma per hour
>
> 10Hr requires a 3.5Ahr battery
> 20Hr requires a 7.5Ahr battery
> etc...
>
> Is this more or less accurate, or have I missed something? Thanks.
>
> ...robert

Don Wilhelm-4

Re: K2 qrp battery drain estimation

In reply to this post by ny4g

Actually, the K2 has a built-in alarm that can be used to indicate a low
battery voltage.
It is the CAL CUR menu setting. Its use for that purpose is a little
bit 'convoluted' because it depends on the way the K2 power control
operates to keep the requested power level no matter what the voltage
may be.
To set it before your battery operation, connect the K2 to an 11 volt
power source (assuming you want the alarm to trigger when the battery is
11 volts or less), then tap the DISPLAY button and transmit with the
power set to your desired level -- observe the current.
Now set CAL CUR to that value. When you begin to see HiCur messages, it
is time to change the battery.

After your portable battery powered event, restore the CAL CUR menu
setting to the normal 3.50 setting.
Yes, I know the normal base K2 manual says 2.50 for CAL CUR, but with
the KDSP2 installed and some other options, HiCur messages can be
produced with the power control set fully to the max. I do not
recommend that power be set higher than 10 watts, but some operators
insist on squeezing every bit out of it, then object to the HiCur
messages. Do not go higher than 3.50 on the CAL CUR menu setting.

73,
Don W3FPR
.
On 6/14/2013 7:21 PM, Ariel Jacala wrote:

> Bruce is right. QST had an article last month for a programmable LED to monitor battery voltage. It is easy to make. You should monitor the resting voltage to provide some margin from over discharging
>
> Ariel NY4G
>
> Sent from my iPhone
>
> On Jun 14, 2013, at 7:17 PM, "Bruce Beford" <[hidden email]> wrote:
>
>>> Is this more or less accurate, or have I missed something? Thanks.
>> You missed the fact that you really can't/shouldn't try to discharge the
>> full capacity of the battery. The life span of SLA batteries for instance,
>> are greatly reduced if you routinely go to greater than 50% depth of
>> discharge.
>> 73
>> bruce
>> N1RX
>>
>>
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Michael Babineau-2

Re: K2 qrp battery drain estimation

In reply to this post by RobertG

Robert :

If you are planning to use Lead-Acid technology (SLA or wet-cell )
then, as others have suggested, you should double your calculated capacity, as you never want
to drain a Lead-Acid battery by more than 50% ..

so

10 hr requires 7 Ah
20 hr requires 15 Ah
etc.

The reality is that you will probably spend somewhat more than 50% of the time listening and tuning around
for stations when you are S&P so the real split may be more like 30% TX and 70% RX, but 50/50 is probably
a good guess.

One further point .. don't discharge a Lead acid battery below 10.5 v. Repeatedly doing this will shorten
its lifespan. Don's suggestion of setting the low voltage indication on the K2 to 11v is a good idea.

For picnic-table-portable operations, battery booster packs (intended to jump-start cars) work very well
and it is easy to find one with an SLA in the 10Ah to 20Ah range, often on sale. You can take the plastic
case apart to install some fusing and even powerpole connectors to customize it for your application
(I also removed the jumper cables from mine). Some of these packs now even come with USB ports to allow for impromptu
powering/charging of i-Devices. It is often cheaper to buy one of these than to purchase just the equivalent capacity SLA
battery .. so you get a nice carrying case with a handle and other goodies for free.

Best of luck ...

Michael VE3WMB

>From: Robert G Strickland <[hidden email]>
>Date: June 14, 2013 6:28:10 PM EDT
>To: Elecraft <[hidden email]>
>Subject: [Elecraft] K2 qrp battery drain estimation

>If I'm operating a K2 at 5w cw, in S&P contest mode, I compute the current drain under the stated conditions as follows:

>conditions:
>50% listening, 50% transmitting
>CW 50% duty cycle

>current:
>200ma receive, more or less
>1.0a transmit, more or less

>current draw per hour:
>100ma [30min rcv] + 250ma [30min xmit @ 50% duty cycle] = 350ma per hour

>10Hr requires a 3.5Ahr battery
>20Hr requires a 7.5Ahr battery
>etc...

>Is this more or less accurate, or have I missed something? Thanks.

>...robert
--
>Robert G Strickland, PhD ABPH - KE2WY
>[hidden email]
>Syracuse, New York, USA
______________________________________________________________
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Phillip Lontz

Elecraft K3 drain at 5 watts CW only.

So, for Field Day running CW only any ideas about what the required amp hours will be?

Sent from my iPad

On Jun 15, 2013, at 8:06 AM, Michael Babineau <[hidden email]> wrote:

> Robert :
>
> If you are planning to use Lead-Acid technology (SLA or wet-cell )
> then, as others have suggested, you should double your calculated capacity, as you never want
> to drain a Lead-Acid battery by more than 50% ..
>
> so
>
> 10 hr requires 7 Ah
> 20 hr requires 15 Ah
> etc.
>
> The reality is that you will probably spend somewhat more than 50% of the time listening and tuning around
> for stations when you are S&P so the real split may be more like 30% TX and 70% RX, but 50/50 is probably
> a good guess.
>
> One further point .. don't discharge a Lead acid battery below 10.5 v. Repeatedly doing this will shorten
> its lifespan. Don's suggestion of setting the low voltage indication on the K2 to 11v is a good idea.
>
> For picnic-table-portable operations, battery booster packs (intended to jump-start cars) work very well
> and it is easy to find one with an SLA in the 10Ah to 20Ah range, often on sale. You can take the plastic
> case apart to install some fusing and even powerpole connectors to customize it for your application
> (I also removed the jumper cables from mine). Some of these packs now even come with USB ports to allow for impromptu
> powering/charging of i-Devices. It is often cheaper to buy one of these than to purchase just the equivalent capacity SLA
> battery .. so you get a nice carrying case with a handle and other goodies for free.
>
> Best of luck ...
>
> Michael VE3WMB
>
>
>
>> From: Robert G Strickland <[hidden email]>
>> Date: June 14, 2013 6:28:10 PM EDT
>> To: Elecraft <[hidden email]>
>> Subject: [Elecraft] K2 qrp battery drain estimation
>
>
>> If I'm operating a K2 at 5w cw, in S&P contest mode, I compute the current drain under the stated conditions as follows:
>
>> conditions:
>> 50% listening, 50% transmitting
>> CW 50% duty cycle
>
>> current:
>> 200ma receive, more or less
>> 1.0a transmit, more or less
>
>> current draw per hour:
>> 100ma [30min rcv] + 250ma [30min xmit @ 50% duty cycle] = 350ma per hour
>
>> 10Hr requires a 3.5Ahr battery
>> 20Hr requires a 7.5Ahr battery
>> etc...
>
>> Is this more or less accurate, or have I missed something? Thanks.
>
>> ...robert
> --
>> Robert G Strickland, PhD ABPH - KE2WY
>> [hidden email]
>> Syracuse, New York, USA
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

ny4g

Re: Elecraft K3 drain at 5 watts CW only.

For a K2 or K3, using 2 amps as a reasonable current drain on TX and 50% duty cycle. Operating for a 24 hour period - 12h will be on TX. A safe bet will be to have a 20Watt panel keeping a 30amp-hour SLA reasonably topped up for night time operation allowing for a 15 a-h drain maximum will get you 7.5h of TX time. Better to have more and not need it than otherwise. That will be my set-up for Field Day using a KX3. Since the current drain on a KX3 is lower than that of a K2 or a KX3 on TX and RX, approximately 1 amp on TX, I could probably get by without a solar panel with a 30 a-h SLA or use 15a-h with a panel. For a K2 or K3 in QRP mode I would go the full 30 -h SLA and a panel. In the above, overestimating the duty cycle approximates the receive duty since that was not explicitly calculated.

More accurately:
K2 or K3
Outflow = 12h(2 amps) + 12h(0.2 amps) = 26.4 a-h
Inflow = 12h*50%efficiency*1 amp = 6 amp-h
Net Outflow ~ 20 amp hr
Need 40 a-h battery with a 20w panel
So if the TX duty cycle is lower than 50% - you might be able to get by with a 30 a-h battery with a panel

KX3
Outflow = 12h(1 amps) + 12h(0.15 amps) = 13.8 a-h
Inflow = 12h*50%efficiency*1 amp = 6 a-h
Net Outflow ~ 7.8 a-h
Need 16 a-h with a panel or 30 a-h battery without a panel

Ariel NY4G

Sent from my iPad

On Jun 15, 2013, at 10:15 AM, "Philip Townsend Lontz" <[hidden email]> wrote:

>
> So, for Field Day running CW only any ideas about what the required amp hours will be?
>
> Sent from my iPad
>
> On Jun 15, 2013, at 8:06 AM, Michael Babineau <[hidden email]> wrote:
>
>> Robert :
>>
>> If you are planning to use Lead-Acid technology (SLA or wet-cell )
>> then, as others have suggested, you should double your calculated capacity, as you never want
>> to drain a Lead-Acid battery by more than 50% ..
>>
>> so
>>
>> 10 hr requires 7 Ah
>> 20 hr requires 15 Ah
>> etc.
>>
>> The reality is that you will probably spend somewhat more than 50% of the time listening and tuning around
>> for stations when you are S&P so the real split may be more like 30% TX and 70% RX, but 50/50 is probably
>> a good guess.
>>
>> One further point .. don't discharge a Lead acid battery below 10.5 v. Repeatedly doing this will shorten
>> its lifespan. Don's suggestion of setting the low voltage indication on the K2 to 11v is a good idea.
>>
>> For picnic-table-portable operations, battery booster packs (intended to jump-start cars) work very well
>> and it is easy to find one with an SLA in the 10Ah to 20Ah range, often on sale. You can take the plastic
>> case apart to install some fusing and even powerpole connectors to customize it for your application
>> (I also removed the jumper cables from mine). Some of these packs now even come with USB ports to allow for impromptu
>> powering/charging of i-Devices. It is often cheaper to buy one of these than to purchase just the equivalent capacity SLA
>> battery .. so you get a nice carrying case with a handle and other goodies for free.
>>
>> Best of luck ...
>>
>> Michael VE3WMB
>>
>>
>>
>>> From: Robert G Strickland <[hidden email]>
>>> Date: June 14, 2013 6:28:10 PM EDT
>>> To: Elecraft <[hidden email]>
>>> Subject: [Elecraft] K2 qrp battery drain estimation
>>
>>
>>> If I'm operating a K2 at 5w cw, in S&P contest mode, I compute the current drain under the stated conditions as follows:
>>
>>> conditions:
>>> 50% listening, 50% transmitting
>>> CW 50% duty cycle
>>
>>> current:
>>> 200ma receive, more or less
>>> 1.0a transmit, more or less
>>
>>> current draw per hour:
>>> 100ma [30min rcv] + 250ma [30min xmit @ 50% duty cycle] = 350ma per hour
>>
>>> 10Hr requires a 3.5Ahr battery
>>> 20Hr requires a 7.5Ahr battery
>>> etc...
>>
>>> Is this more or less accurate, or have I missed something? Thanks.
>>
>>> ...robert
>> --
>>> Robert G Strickland, PhD ABPH - KE2WY
>>> [hidden email]
>>> Syracuse, New York, USA
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

Ray Cadmus

Re: K2 qrp battery drain estimation

In reply to this post by RobertG

You might want to check out the battery estimator spreadsheet from:

http://www.wa0itp.com/

Other good links there as well :-)

ray W0PFO

--

On 06/14/2013 05:28 PM, Robert G Strickland wrote:

w1pns

Re: K2 qrp battery drain estimation

In reply to this post by Michael Babineau-2

Dunno if this would be of any help, but the Four States QRP Club has a battery-use estimator on its website. I've found it helpful...

http://www.4sqrp.com/Battery_Capacity/index.php

With best regards,

Pete
W1PNS

----- Original Message -----
From: "Michael Babineau" <[hidden email]>
To: [hidden email]
Cc: [hidden email]
Sent: Saturday, June 15, 2013 10:06:06 AM
Subject: Re: [Elecraft] K2 qrp battery drain estimation

Robert :

If you are planning to use Lead-Acid technology (SLA or wet-cell )
then, as others have suggested, you should double your calculated capacity, as you never want
to drain a Lead-Acid battery by more than 50% ..

so

10 hr requires 7 Ah
20 hr requires 15 Ah
etc.

The reality is that you will probably spend somewhat more than 50% of the time listening and tuning around
for stations when you are S&P so the real split may be more like 30% TX and 70% RX, but 50/50 is probably
a good guess.

One further point .. don't discharge a Lead acid battery below 10.5 v. Repeatedly doing this will shorten
its lifespan. Don's suggestion of setting the low voltage indication on the K2 to 11v is a good idea.

For picnic-table-portable operations, battery booster packs (intended to jump-start cars) work very well
and it is easy to find one with an SLA in the 10Ah to 20Ah range, often on sale. You can take the plastic
case apart to install some fusing and even powerpole connectors to customize it for your application
(I also removed the jumper cables from mine). Some of these packs now even come with USB ports to allow for impromptu
powering/charging of i-Devices. It is often cheaper to buy one of these than to purchase just the equivalent capacity SLA
battery .. so you get a nice carrying case with a handle and other goodies for free.

Best of luck ...

Michael VE3WMB

>From: Robert G Strickland <[hidden email]>
>Date: June 14, 2013 6:28:10 PM EDT
>To: Elecraft <[hidden email]>
>Subject: [Elecraft] K2 qrp battery drain estimation

>If I'm operating a K2 at 5w cw, in S&P contest mode, I compute the current drain under the stated conditions as follows:

>conditions:
>50% listening, 50% transmitting
>CW 50% duty cycle

>current:
>200ma receive, more or less
>1.0a transmit, more or less

>current draw per hour:
>100ma [30min rcv] + 250ma [30min xmit @ 50% duty cycle] = 350ma per hour

>10Hr requires a 3.5Ahr battery
>20Hr requires a 7.5Ahr battery
>etc...

>Is this more or less accurate, or have I missed something? Thanks.

>...robert
--
>Robert G Strickland, PhD ABPH - KE2WY
>[hidden email]
>Syracuse, New York, USA
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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RobertG

Re: K2 qrp battery drain estimation

In reply to this post by Michael Babineau-2

Most folks point out that SLA batteries are best *not* drawn down to
their bottom. I'm thinking of using newer LiFePO4 batteries. What's the
draw-down limit, if any, on these items?
...robert

On 6/15/2013 14:06, Michael Babineau wrote:

> *Robert : *
> *
> *
> *If you are planning to use Lead-Acid technology (SLA or wet-cell )*
> *then, as others have suggested, you should double your calculated
> capacity, as you never want*
> *to drain a Lead-Acid battery by more than 50% ..*
> *
> *
> *so *
> *
> *
> *10 hr requires 7 Ah*
> *20 hr requires 15 Ah *
> *etc.*
> *
> *
> *The reality is that you will probably spend somewhat more than 50% of
> the time listening and tuning around*
> *for stations when you are S&P so the real split may be more like 30% TX
> and 70% RX, but 50/50 is probably*
> *a good guess. *
> *
> *
> *One further point .. don't discharge a Lead acid battery below 10.5 v.
> Repeatedly doing this will shorten*
> *its lifespan. Don's suggestion of setting the low voltage indication
> on the K2 to 11v is a good idea.*
> *
> *
> *For picnic-table-portable operations, battery booster packs (intended
> to jump-start cars) work very well*
> *and it is easy to find one with an SLA in the 10Ah to 20Ah range, often
> on sale. You can take the plastic*
> *case apart to install some fusing and even powerpole connectors to
> customize it for your application*
> *(I also removed the jumper cables from mine). Some of these packs now
> even come with USB ports to allow for impromptu *
> *powering/charging of i-Devices. It is often cheaper to buy one of
> these than to purchase just the equivalent capacity SLA*
> *battery .. so you get a nice carrying case with a handle and other
> goodies for free. *
> *
> *
> *Best of luck ...*
> *
> *
> *Michael VE3WMB *
>

--
Robert G Strickland, PhD ABPH - KE2WY
[hidden email]
Syracuse, New York, USA
______________________________________________________________
Elecraft mailing list
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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