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Author Topic: Battery Pack Revisited  (Read 26767 times)

KD8IIC

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Battery Pack Revisited
« on: March 11, 2015, 10:20:59 PM »

  Forgive the new guy here Please.
  I imagine this question has been beat to death here in the past.
  From your personal experience running QRP portable what is your preferred battery or battery pack setup?
  I am looking to have current draw of 1 ampere during xmit in CW mode.12 volts and would like to be able to recharge
  from automobile DC. Was considering a garden tractor lead acid cell but I'm open to any suggestions.
  Seems like battery technology is very quick to change.  73 and Thanks, lane  de n8aft  sk  ..  :)
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G4AON

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RE: Battery Pack Revisited
« Reply #1 on: March 12, 2015, 02:09:13 AM »

I have a page on battery choice for slightly higher current, but the principles are the same...

http://www.qsl.net/g4aon/batteries/

73 Dave
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KB1GMX

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RE: Battery Pack Revisited
« Reply #2 on: March 12, 2015, 03:07:35 AM »

Yes it has...  And still its a problem...

Question... you said the TX pulls 1A...
  *How long do you want to operate?
  *How much power are you using in receive?

Without a complete picture we can at best give you an authoritative guess
which is barely as good as an opinion.

A lawn tractor battery is in the 28-33Ah range so you can comfortably run
that transmitter for a weekend and likely longer.

A 7A gell bat should give a few hours or longer depening on the RX drain and
how much transmitting you actually do.

Allison
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K5LXP

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RE: Battery Pack Revisited
« Reply #3 on: March 12, 2015, 06:04:15 AM »

Garden tractor batteries are not deep cycle and likely flooded, so I would skip those for portable operating.

For lead batteries, small gel cells lend themselves to portable operating and can charge directly from an automobile in most cases.

Primary cells (alkaline or lithium AA's) offer good energy density, easy availability and no need to recharge.

NiCd and NiMH are still worth a look in some applications.  Good energy density, but will need some kind of charge controller to recharge from vehicle power.

The current favorite is some form of lithium battery.  Best Ah/lb, low internal Z and lots of charge cycles.  Expensive per Ah but it's offset by cycle life.  Requires a charge controller.

Per GMX's post, the more data you provide about your application, the more specific a solution you'll get in return. 


Mark K5LXP
Albuquerque, NM
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W4KYR

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RE: Battery Pack Revisited
« Reply #4 on: March 12, 2015, 06:21:39 AM »

I would suggest some solar option for more flexibility.

Have two 12volt 7 AH batteries, while one is being used to transmit and receive, the other one could be charging up with a small solar panel and charge controller. Swap the batteries every few hours. This can be built together in a small box with removable lid and attach the solar panel upside down in the box so that it gets protected during transit. When you operate the radio, remove the lid and flip it over so the solar panel will face the sun and start charging the battery.

The quick and dirty way is to get one of those small auto jump starters and mount your QRP portable to the back of it and mount a small removable solar panel to the front of it. Cut off the battery clamps to make it more compact.

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W8JX

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RE: Battery Pack Revisited
« Reply #5 on: March 12, 2015, 07:54:03 AM »

Have two 12volt 7 AH batteries, while one is being used to transmit and receive, the other one could be charging up with a small solar panel and charge controller. Swap the batteries every few hours. This can be built together in a small box with removable lid and attach the solar panel upside down in the box so that it gets protected during transit. When you operate the radio, remove the lid and flip it over so the solar panel will face the sun and start charging the battery.

This equals weight and bulk to carry and no good cloudy days or nights. If you carried the same weigh in lithium, you will not have to worry about switching or solar cells or day/night. Many over complicate things. You get minimum of 4x more power per pound with lithium vs gel cell. So which do you want to carry? You can get 4x run time same weight or 2x run time with 1/2 the weight. Tuff choice huh?  Maybe for a guy that thinks XP is a good viable OS still.
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WB6BYU

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RE: Battery Pack Revisited
« Reply #6 on: March 12, 2015, 09:15:58 AM »

I've done a lot of portable operating with a 4.5Ah lead gel battery and a Ten-Tec Argonaut 505 that
draws about 1A on CW transmit.  The battery was normally good for about 5 days to a week of
backpacking with intermittent operation in the evenings, or 24 hours of more focused operation.
But I'm not a very serious operator, either:  a 7Ah battery would be better for something like
Field Day, and even that might not be enough, depending on how much time you spend cooking
and sleeping.  (It isn't uncommon to hear chirpy signals from battery-powered QRP stations
on Sunday.)

For me, 4.5Ah was available, and was small and light enough to work in a backpack.  It wouldn't
be the best choice for everyone else, especially as battery technology has advanced since that
time.  I'm presenting these numbers as a rough guide for how much operating time to expect
from a particular battery capacity - that will also depend on how much current your rig draws
on receive.

Lithium is probably the best choice for power density, but is more expensive.  For frequent long
treks, that would be the best choice.  But for shorter or less-frequent trips, and if cost is an
issue, there are other alternatives.  1A is a bit much for Alkaline batteries, but at lower power
levels a set of disposable AA batteries from Costco might not be a bad choice, especially if
you arrange to use the same cells in your flashlights, GPS, and any other electronic devices.
One advantage of designing your system for AA batteries is that you can use NiMh rechargeables,
alkalines, or Lithium camera batteries in it depending on your needs for each trip.

For non-backpacking applications where weight isn't the highest priority, a 7Ah gel battery is very
common and should provide operation for most of a day or so (again, depending on your radio and
your operating style.)  For Field Day where I can drive to the site I use some 33Ah gel batteries that
cost me $5 each (used), and easily power the rig for the full time even at 2A draw.  (But could be
marginal in a multi-operator group - by myself I rarely operate for more than about 12 hours.)


So careful consideration of your planned operating times and conditions is as important as the current
draw of your radio on both transmit and receive in choosing a battery type and size.

W4KYR

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RE: Battery Pack Revisited
« Reply #7 on: March 12, 2015, 09:20:49 AM »


This equals weight and bulk to carry and no good cloudy days or nights. If you carried the same weigh in lithium, you will not have to worry about switching or solar cells or day/night. Many over complicate things. You get minimum of 4x more power per pound with lithium vs gel cell. So which do you want to carry? You can get 4x run time same weight or 2x run time with 1/2 the weight. Tuff choice huh?  

Maybe for a guy that thinks XP is a good viable OS still.

About XP , I thought the OP's question was about batteries and QRP. By since you mentioned it.


 By all means upgrade to the latest and greatest if anyone feels so inclined. Anyone can spend their money on anything they wish, if they have the extra spare change and feel some compelling need to spend that extra money.

Or have the option of not spending extra money on unnecessary purchases and make do with as little as possible and get the job done. Many hams have 10 or 15 year old rigs and 5 or 10 year old computers that still work fine for their needs.

Back to the OP's question.

I mentioned solar for additional charging options. With a small inexpensive jump starter, gives the options of charging it from AC (if available) or charge it from the car (if you are in a car). Or use the solar panel to charge the pack up in the field during the day in sunny weather.  Jump starters are widely available everywhere for $35 and up and come with the AC cord (sometimes the DC cord) as well.

Lithium batteries are great, and as others mentioned...they cost more money. By all means go that route but keep in mind that these batteries are different than your typical gel cell battery. If you want charging flexibility such as AC/DC and/or solar for your lithium batteries. Read this.

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries


« Last Edit: March 12, 2015, 09:34:10 AM by W4KYR »
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W2IU

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RE: Battery Pack Revisited
« Reply #8 on: March 12, 2015, 11:08:43 AM »

I use 12v 7ah SLA's purchased from local alarm company for a couple of bucks a pop. You could buy a couple of them and bring them along. A little on the heavy side, but not nearly as expensive as LiFe and the harbor freight $7 float chargers keep them tip top!
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W8JX

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RE: Battery Pack Revisited
« Reply #9 on: March 12, 2015, 02:19:10 PM »


About XP , I thought the OP's question was about batteries and QRP. By since you mentioned it.


Your sig waves the flag that you are stuck with past solutions and likely to give same old solution for portable. Times change.....
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KD8IIC

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RE: Battery Pack Revisited
« Reply #10 on: March 13, 2015, 05:13:21 AM »

  Thanks for all the great info here. I'm just interested in casual CW QRP table or tailgate operation at the nearby parks and hilltops. Likely only less than about six hours at a time.
 Sounds like the 7Ah SLA type is readily available and easy to work with, easily kept charged.
With the small size and weight one could easily parallel two or a few for more Ah capacity if needed.
  Thanks Again and 73
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K5LXP

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RE: Battery Pack Revisited
« Reply #11 on: March 13, 2015, 06:54:37 AM »

Not sure if you have any, but power tool battery packs make for dandy portable power sources.  They're likely just sitting around anyway between projects, and come with rapid chargers.

One year I operated Field Day running my Ten Tec QRP rig from a DeWalt cordless drill battery and the other guys thought that was the coolest thing.  There's something to be said for repurposing something you already have vs going out and buying another setup which in this case, may be just a duplication.


Mark K5LXP
Albuquerque, NM
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W8JX

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RE: Battery Pack Revisited
« Reply #12 on: March 13, 2015, 07:27:55 AM »

Sounds like the 7Ah SLA type is readily available and easy to work with, easily kept charged.

For what its worth I have not bought a 7ah one fore over 10 years now. The only place I use them is in UPS backup power supplies and when I buy them it is 8 or 9ah version not 7 as they are all same size.
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Ham since 1969....  Old School 20wpm REAL Extra Class..

KD8IIC

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RE: Battery Pack Revisited
« Reply #13 on: March 14, 2015, 02:15:43 AM »

 Even Better, Thanks! The new rig should be here Tuesday evening. Hope to be almost ready to hit the great outdoors by the weekend!
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KD8IIC

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RE: Battery Pack Revisited
« Reply #14 on: March 14, 2015, 02:29:37 AM »

 Is there any special consideration as to recharging an SLA battery? I'm considering making a fused pigtail to go from the car's cigarette lighter to recharge to and from an outing. I can mount the battery in a vented enclosure for safety during transport and storage, might be a good thing to consider.
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