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Author Topic: Good battery ?  (Read 8835 times)
KD8QOI
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Posts: 11




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« on: March 23, 2014, 05:04:15 PM »

Hey all

 I was wondering what would be a good battery for QRP? In the size of a 7amp lead acid battery?

I am thinking of
http://www.batteryspace.com/LiFePO4-26650-Battery-12.8V-9.9Ah-126.72Wh-21A-rate-with-PCB.aspx

Which is very close to the size of the 7ah lead acids
« Last Edit: March 23, 2014, 05:08:16 PM by KD8QOI » Logged
AA4PB
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Posts: 13032




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« Reply #1 on: March 23, 2014, 05:21:11 PM »

A 7AH battery would normally be fine for QRP. The lithium you are looking at is pretty expensive for my taste.  A 7AH SLA battery can be had for $12. http://www.batterysharks.com/12-Volt-7-Amp-Seal-Lead-Acid-Battrery-p/12v-7ah_b12-7.htm

By "normally" I mean that you aren't expecting the battery to power the station 24/7 for two weeks straight.  Wink
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K5LXP
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Posts: 4536


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« Reply #2 on: March 24, 2014, 06:19:48 AM »

QRP what?  A week long back country hike, SOTA expedition, afternoon at the city park?  Lithiums can be great power sources but you'll pay a premium for them.

Even retail a 7Ah gel is about $20 (as is AA4PB's deal, after shipping).  That's about $3/Ah and 1.4Ah/lb.

The lithium is $14.80/Ah, but the upside is 4Ah/lb.  A clear winner for Ah/lb but if you're driving to the operating spot, then it's not an advantage.

So the application matters, unless your budget doesn't. 


Mark K5LXP
Albuquerque, NM
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K8AG
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Posts: 352




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« Reply #3 on: March 24, 2014, 09:10:58 AM »

The chargers for LiPo and related batteries tend to be a bit more involved than those for SLA.  There are actual dangers in not using one that monitors each cell while charging.  If you don't already have one it adds to the expense.

73, JP, K8AG
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W1VT
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Posts: 898




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« Reply #4 on: March 26, 2014, 11:15:41 AM »

http://www.towerhobbies.com/help/ama_lipo/

The Academy of Model Aeronautics says that LiPos are significantly more dangerous than older technologies.

The AMA has made it possible to fly model airplanes in many areas by providing the insurance required by land owners.

http://www.modelaircraft.org/



« Last Edit: March 26, 2014, 11:17:43 AM by W1VT » Logged
KI5WW
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Posts: 75




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« Reply #5 on: March 27, 2014, 09:16:03 PM »

On the small li batterery packs from china. Generally these are sold as internal packs which is great. But ive found to take the advertised ah's and divide it by two. Yea typical china stuff. Dont try to recharge li packs with a nimh or standard charger. Mark your Li charger as such with a label easy to see. Buy two packs and take both with you and a screwdriver. These cells are not 1.5volt cells. There more like 3.5 volts. Or 3.7 volts?  Each cell.
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KU7PDX
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« Reply #6 on: March 29, 2014, 09:48:13 PM »

http://www.towerhobbies.com/help/ama_lipo/
The Academy of Model Aeronautics says that LiPos are significantly more dangerous than older technologies.

The AMA has made it possible to fly model airplanes in many areas by providing the insurance required by land owners.
http://www.modelaircraft.org/

First, this "alert" from the AMA was sent in early 2004 when LiPo technology was extremely new and not many understood how to properly charge batteries. Second, those that did experience "thermal runaways" were because they used lead-acid, NiMH, or NiCd chargers, all of which would cause a lithium-polymer battery to be overcharged. Third, now most universal chargers will have a setting specifically for lithium-polymer batteries and (fourth) we even have better lithium batteries like lithium-manganese or lithium-nickel-manganese-cobalt (like what's in my Nissan Leaf EV) that won't experience a thermal runaway even if you saw them in half with a hacksaw. Grin

The AMA now welcomes the (proper) use of lithium-technology batteries and you'll be hard pressed to find anyone still using NiMH or NiCd batteries anymore in the modeling hobby.

To the OP, have no fear with lithium batteries, just do your proper research, remember to use a charger for the correct chemistry of battery, and use a voltmeter or lipo alarm to make sure you don't discharge the battery below its recommended level.
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73,
Chris - KU7PDX
W4KYR
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Posts: 621




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« Reply #7 on: March 30, 2014, 06:09:59 AM »

Lead acid/Gel cells can be charged with a solar panel and a charge controller. Does Lithium batteries need a special solar charger? Or can any standard charge controller work?
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Still using Windows XP Pro.
KB1GMX
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Posts: 828




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« Reply #8 on: April 04, 2014, 08:56:51 AM »

Lithium needs more care in charging in general and with solar that means
using the right solar controller. 

That means the peak charging voltage across the battery should never exceed the
maximum full charge voltage (for LION typically 4.2V cell,  LIPo4 lower) and
not exceeding the recommended charge rate (typical is .2C to .7C range).
With solar limiting to the max voltage is often the need  as open circuit for 12V
standard panels is 21.5 to 22.3V and best power point is around 17 to 18V.
There are panels for charging batteries that have lower voltages but in
poor sun conditions you get less or no charging so its better to have higher
voltage and manage it.  So limiting the voltage electronically for the lithium
battery in use is practical and useful besides a requirement.

Current limiting is often less an issue as the size of the solar panel is a limiting
factor for example a 12W panel will do at most around 700-800ma and that fine
for many lithium batteries greater than 1000mAh.  For larger batteries like my
10.4AH to get to .7C  charge rate I need a 100W panel, too large for portable
though doable for field day so current is often self limiting due to physical
panel size. 

For running my FT817 for extended periods I built up a 4P3S using 18650
tabbed lion cells and a suitable CMB (charge management and protection board).
The cells used are Tenergy 2600mah each and the result is a 10.4ah 11.1V nominal
(full charge is 12.8 and cutoff is 9.6) and perfect for FT817 radios .   Less than half
the weight of Lead easily but about 80$ to assemble.  Based on other smaller packs
made with similar cells and in use I expect many years of service beyond what
gelled lead has done for me.  A battery of this size is more than sufficient to run a
FT817 a weekend of Field Day activity with 20W of solar help assuming 4 hours
of good sun per day

The charge controller for solar I want to use for lithium cells is still in the works as
I need a about 7A current limit and the peak voltage must be no greater than
13.1 V for safety.  The design I'm working on is a MPPT design.  This is so a
50W panel can give me the maximum power transfer at 13V under all conditions
efficiently.  Current testing says at best power point of 18V my 50w of panels will
do 2.78A down converted thats 3.46A (assuming MPPT is 90% efficient).

Lithium chemistry unlike lead has a better life if not fully charged and not fully discharged.
Lead prefers a full charge and a partial discharge for best cycle life.  This is an advantage
for solar portable where the sun may not be able to fully charge the battery.


Allison


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KV7W
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Posts: 136




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« Reply #9 on: May 20, 2014, 07:19:05 PM »

The setup I'm working is on is something like this, too. I have a foldable solar panel rated for 27W. It has three outputs, 2 usb and one 12v, (unregulated). I just picked up a 10,000mAH Lithium power pack for cell/gps, etc. It has three outputs, 2 usb, (2A), and a micro usb. The pack was only $30 on Amazon. Has 4 little micro leds to show charge level and comes in a case that's just a little smaller than my radio.

I might be able to run my radio directly off the panel, but building a regulator isn't a deal breaker. The pack is charged from the micro usb. I have a little x1m that draws about 1.4A on transmit. I picked up a boost converter for $6, just got it. Has a display and tactile button to switch between input and output voltage, and can be held in for a few seconds to turn the display off for power save. I haven't built up a resistor load yet, just powered up and adjusted so far. Not sure how much noise it's going to produce - might just throw a toroid in there somewhere.

Hope it works. If I power all my qrp stuff off usb - that really opens up a lot of opportunities. I might not even need that 12V output.

 

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KB1GMX
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Posts: 828




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« Reply #10 on: May 22, 2014, 07:03:37 PM »

>>>I might be able to run my radio directly off the panel, but building a regulator isn't a deal breaker.

Not likely.  Think of a solar panel (nominal 12V 36 cell type) as a battery of 22V with a series resistor  when in bright sun.
In dim sun the voltage might be 22V but the internal resistor is not really large value limiting current.  So what the radio
could see is near 20V on receive and near 9V on transmit depending on the size in watts of the panel.  A battery to
absorb power on receiver and support the peak current of transmit is a must.  The regulator/charge controller is to protect
the battery and the radio.


>>> The pack is charged from the micro usb. I have a little x1m that draws about 1.4A on transmit. I picked up a boost converter for $6, just got it. Has a display and tactile button to switch between input and output voltage, and can be held in for a few seconds to turn the display off for power save. I haven't built up a resistor load yet, just powered up and adjusted so far. Not sure how much noise it's going to produce - might just throw a toroid in there somewhere.

Now that might work and then you might spend a lot of time trying to kill the internal converters switching noise.
If noise is an issue both sides (input and output) must be treated as the solar panel and its leads may be the antenna!

Note: mode of those USB packs are one 3.7V lipo (one I have has a 4700mah cell) so to get 5V they up-convert
as well as regulate the output to 5V with a max current of .5A per port (what mine does).  Some max out at 1.5 or 2A
but in the end you are limited in voltage.  Also some will not turn on and stay on if there isn't a minimum load present,
again, mine must see a 50ma draw or it shuts off.

Its better to use a battery built for the purpose.

Remember Lithium tech has a maximum voltage that its safe to charge to. Trickle charging is not allowed.  There is a
minimum voltage for discharge as going lower can ruin or compromise the battery.  The amount of applied charging
current also has safe bounds too low and the battery looses capacity or never charges adequately for use.  Excessive
current can cook the battery (thermal runaway or fire) or weaken it.  Lithium are too expensive to ruin.  They are when
handled properly longer lasting and great power per pound (or kilogram).

If you do it right Lithium tech batteries are great, wrong is a real pain if it stops working or fails destructively.
if simple is desired then NiMh or even lead is the way to go.  Both are far cheaper and more tolerant of charging
and discharge abuses.


Allison
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KF7DS
Member

Posts: 192




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« Reply #11 on: May 25, 2014, 09:55:57 AM »

I am an avid model airplane flyer and ham, and have a 'OT of experience with batteries. I use Lipos for my aircraft and use them with extreme caution but they work well in this application, especially given the physical size required for model aircraft.

A much better bet for portable ham use are LIFEPO4 batteries-better characteristics than lipos, very light and safe.

Check out the 3 and 6 mah batteries from Bioennopower (www.bioennopower.com). I can run my kx3 at 12w for a good 3+ hours cw without any issues. The 6mah battery would last a good 6 plus hours. Very light and come with their own charger and power poles.

Don KF7DS
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KV7W
Member

Posts: 136




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« Reply #12 on: May 25, 2014, 10:40:37 PM »

>>> The regulator/charge controller is to protect
the battery and the radio.

Yep, I tested on a nice sunny day and I'll need to rig up a 317. I have everything in my junk box for a smart charger except an IC I've been eyeballing. I'll also be hunting for some load resistors at the ham fests this summer - could have used them the other day. I don't know how many times I've seen them for give away prices, but figured I wouldn't need one.

Fortunately, My panel will charge my lithium pack off the supplied usb. I tested the pack over the last couple days running my GPS. I was on the road, so wasn't bench testing, but guess the GPS with dead battery running off the pack drew about 500 mil until the battery was peaked. (The pack got pretty warm, but not that bad.) I didn't know they up converted. When I looked at the specs that came with the pack it states the 10Ah rating is @3.7V....I was hoping to have a little fudge in there to "make" the pack work, but it's not worth destroying it to open the case at those specs.

I really like the LiPo's I have, just don't like having to carry around a dedicated charger. That's one of main issues for me; there are so many different styles of batteries, each with their own voltage and charging requirements. I like to go portable, long distance on a motorcycle portable. My cell, gps, and my ebook all run off usb. If I bring a tablet it'll run off usb, (even my analyzer runs off usb). Then there is my qrp and other radio gear running old school 12V. Kind of like the transition from cassette to CD. Now every car has CD - and who buys CD's when you can blutooth off your cell phone?

I've been kicking around an ultracap project for years now. The maxwell 2.7v 350F cells dropped down in price to about $12 each. I think I could probably rig something together with a small footprint and relatively little weight that would power my power hungry qrp during the day and for a few hours at night. I could charge it through 5V solar or usb pack. It would also give me the option to quick charge in a few seconds off my bike battery. These buck/boost converters are surprisingly accurate and cheaper than I can buy the parts to build. (Still need to see what the noise level is.) Seems like a lot of work when a 8Ah sla is about $25, but there's the cool factor.   
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