KX3/P3 external power source

[mmacro]

I need to work up a reliable external power source for my KX3 and P3. I also have RC aircraft and cars… So a LiPo or LiFe battery is an easy solution for me.

The battery would offer substantial weight savings and I already have the chargers and other equipment necessary to build the connections.

Is there anything that I need to be aware of? Would a 4S 14.8V 5200mAh 50C be workable?

What other advice would you have?

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[Matt Zilmer-3]

FWIW, I'm using a Turnigy 7.2AN, 4S LiPo for the KX3 and KX2.  Works
fine, though at full charge it's a little high on the voltage.

73,

matt W6NIA


On 6/7/2017 10:29 AM, Matthew MacRoberts wrote:

> I need to work up a reliable external power source for my KX3 and P3. I also have RC aircraft and cars… So a LiPo or LiFe battery is an easy solution for me.
>
> The battery would offer substantial weight savings and I already have the chargers and other equipment necessary to build the connections.
>
> Is there anything that I need to be aware of? Would a 4S 14.8V 5200mAh 50C be workable?
>
> What other advice would you have?
>
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--
"A delay is better than a disaster."
-- unknown

Matt Zilmer, W6NIA
[Shiraz]

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[Bob N3MNT]

Most people use the 4S LiFe vs LiPo as the fully charged voltage is closer to the KX3 requirements.  A quick search for LiFe will show many discussions. As you use these for your RC stuff, you know the requirements and cautions so you should be good to go.

[mmacro]

Are there any internal resistance or c-ratings that I should be aware of? (Like there are on RC vehicles)

Are Ham’s using any kind of low voltage cutoff with their batteries?

Internal Resistance and C-Rating

> On Jun 7, 2017, at 2:23 PM, Bob N3MNT <[hidden email]> wrote:
>
> Most people use the 4S LiFe vs LiPo as the fully charged voltage is closer to
> the KX3 requirements.  A quick search for LiFe will show many discussions.
> As you use these for your RC stuff, you know the requirements and cautions
> so you should be good to go.
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/KX3-P3-external-power-source-tp7631473p7631475.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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[Bob N3MNT]

I don't think you have to worry about "C-rating" running a KX3.  You are not drawing 20-80A, but  more like 2-3A.  As for low voltage cut off, you can set that in radio or use an external power /voltage meter to monitor it.  

[Grant Youngman-2]

I think a low voltage cutoff (or at least an alarm) with LiFe is a good idea, especially if you have other devices besides the radio directly connected to the battery, like a KX3, other 12v or USB-powered thingies, etc..  I currently use a Buddipole PowerMini which is a compact battery monitor, low voltage alarm/cutoff, and solar charge controller all in one.  There are other options out there, of course.


> On Jun 7, 2017, at 2:40 PM, Bob N3MNT <[hidden email]> wrote:
>
> I don't think you have to worry about "C-rating" running a KX3.  You are not
> drawing 20-80A, but  more like 2-3A.  As for low voltage cut off, you can
> set that in radio or use an external power /voltage meter to monitor it.  
>

Grant NQ5T
K3 #2091, KX3 #8342



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[k6dgw]

LiPoly or LiFePO4 are both good, the LiFe seems to be a somewhat more
stable and forgiving chemistry.  I use a4S1P LiFePO4 with my K2.  It has
a very flat discharge curveuntil the end and then it drops rapidly, the
K2 shuts down and the battery is protected from complete discharge.  I
can get about 93% of the energy before the K2 shuts down.  You really
want a cell balancing charger, but it sounds like you may already have one.

LiPoly's are lighter of course, but I had one catch fire while I was on
my KX1 so I'm a bit wary of them.  The LiFe is not that much heavier.

Beware of "hot deals" on Li batteries. I bought an allegedly 9 Ah Li-ion
batterywhich came from you know where.  It had a linear discharge curve
with a slope of about 1 and the K2 shut down after I'd used around 1.4
Ah of the stored energy. All the rest was inaccessible by my K2.

73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 6/7/2017 10:29 AM, Matthew MacRoberts wrote:
> I need to work up a reliable external power source for my KX3 and P3. I also have RC aircraft and cars… So a LiPo or LiFe battery is an easy solution for me.
>
> The battery would offer substantial weight savings and I already have the chargers and other equipment necessary to build the connections.
>
> Is there anything that I need to be aware of? Would a 4S 14.8V 5200mAh 50C be workable?
>
> What other advice would you have?
>

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[Bob N3MNT]

I do not recommend drawing either LiPo or LiFe batteries below about 35%-40% as it will shorten the life of the battery.

[Roger Meadows]

What would you recommend setting the shutoff voltage of a KX3 when using a LiFePo4 battery?

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

From: Bob N3MNT<mailto:[hidden email]>
Sent: Thursday, June 8, 2017 09:02
To: [hidden email]<mailto:[hidden email]>
Subject: Re: [Elecraft] KX3/P3 external power source

I do not recommend drawing either LiPo or LiFe batteries below about 35%-40%
as it will shorten the life of the battery.




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[k6dgw]

Not sure I understand your question Matthew. Lithiumbatteries [all
chemistries] have exceedingly low internal resistanceand consequently,
will deliver a huge current if shorted.  Power leads should be fused.  
The flat, automotive blade-type fuses seem to work best... large, low
resistance contact area.

The voltage vs time function during discharge is probably the primary
concern for ham QRP use because it determines the total energy you can
extract from the battery before your radio quits. Good quality LiFePO4's
have a discharge curve that is very flat after an initial drop from
full-charge.  Mine [an A123 4S1Ppack] maintains a terminal voltage above
11.5 V until it is nearly discharged.

Re low-voltage cutoff: Some packs have a cutoff internal.  My K2 shuts
down [draws negligible current] at about 10.5Vhowever I've only had that
happen once. Most of the time, other factors [weather, tired butt, bugs]
will terminate an outdoor session well before the battery depletes.

73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 6/7/2017 11:34 AM, Matthew MacRoberts wrote:
> Are there any internal resistance or c-ratings that I should be aware of? (Like there are on RC vehicles)
>
> Are Ham’s using any kind of low voltage cutoff with their batteries?
>

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[Jim Brown-10]

Yes. There are two VERY different limitations on minimum battery
voltage.  One, which is set by the radio, is the minimum voltage at
which the radio function is acceptable.

The other limit is the minimum voltage to which the battery can be
discharged without damage to the battery. Li batteries of all variations
are damaged if discharged below a certain voltage. That voltage depends
on the chemistry used -- LiPO, LiFePO3, etc. For LiFePO3 chemistry, the
individual cells that make up the battery should not be discharged below
about 3V per cell. Once the cell has fallen to that voltage, it is
nearly discharged, and continuing to draw current from it will cause the
voltage to fall very quickly, and damage can occur.

73, Jim K9YC

On Thu,6/8/2017 10:28 AM, Fred Jensen wrote:

> Not sure I understand your question Matthew. Lithiumbatteries [all
> chemistries] have exceedingly low internal resistanceand consequently,
> will deliver a huge current if shorted.  Power leads should be fused.  
> The flat, automotive blade-type fuses seem to work best... large, low
> resistance contact area.
>
> The voltage vs time function during discharge is probably the primary
> concern for ham QRP use because it determines the total energy you can
> extract from the battery before your radio quits. Good quality
> LiFePO4's have a discharge curve that is very flat after an initial
> drop from full-charge.  Mine [an A123 4S1Ppack] maintains a terminal
> voltage above 11.5 V until it is nearly discharged.
>
> Re low-voltage cutoff: Some packs have a cutoff internal.  My K2 shuts
> down [draws negligible current] at about 10.5Vhowever I've only had
> that happen once. Most of the time, other factors [weather, tired
> butt, bugs] will terminate an outdoor session well before the battery
> depletes.

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[Terje Elde]

> On 8 Jun 2017, at 20:06, Jim Brown <[hidden email]> wrote:
>
> The other limit is the minimum voltage to which the battery can be discharged without damage to the battery. Li batteries of all variations are damaged if discharged below a certain voltage. That voltage depends on the chemistry used -- LiPO, LiFePO3, etc. For LiFePO3 chemistry, the individual cells that make up the battery should not be discharged below about 3V per cell. Once the cell has fallen to that voltage, it is nearly discharged, and continuing to draw current from it will cause the voltage to fall very quickly, and damage can occur.

Backing this, and just adding:

LiFePo4 should be fine down to about 2.5V pr. cell, but you want some margins. Also keep in mind that one cell is the weakest, and you don't want the battery of that cell dropping below, even if the average is above.

Oh, and also good to keep an eye on the difference between voltage under load, and voltage during idle/receive.

Also, some of this damage can be dangerous. I wouldn't panic about it, but for normal LiIon and LiPo, if they've spent some time below 2V, I'd think twice before using it again.

Just like you need to dry out a tent before packing it away to avoid mold, best have a habit of charging LiIons before putting them away.

Terje / LB8KH
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[Bob N3MNT]

I don't recommend fully charging either LiFe or LiPo batteries before storing them.  Many of the better chargers have a storage mode that brings them up to about 40% charge.  Storing fully charged batteries will shorten their life.

[alorona]

I'm not doubting any of the statements we've read today, but if they're all true then I confess I don't know a darned thing about batteries.

I'm always hearing conflicting information about batteries that leaves me baffled. Store them fully charged; store them 40% charged; discharge them all the way; discharge them down to only to 35 per cent of capacity; aim for 2.5 V per cell; aim for 3.0 V per cell; Lithium is great for QRP portable; Lithium is a bomb ready to go off.

What the heck? When it comes to batteries, the Principle of Contradiction goes out the window.



Al  W6LX
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[Jim Brown-10]

On Thu,6/8/2017 5:22 PM, Al Lorona wrote:
> I'm always hearing conflicting information about batteries that leaves me baffled.

Contradictions like this are usually resolved by careful study of source
documents, not be reading opinions expressed by those who failed to do
that, but instead quote the opinions of others who have also failed to
do that study. Science is NOT decided by majority vote, nor is it
decided by opinion.

73, Jim K9YC

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[Grant Youngman-2]

I use A123 battery packs.  These are built from 26650 cells, which have a nominal voltage of 3.3v and a nominal capacity of 2500 mAH.  The specs for these batteries are published by A123.  The specified minimum voltage per cell is 2V, but the general consensus is that while that final voltage won’t destroy the battery, discharging to that level can reduce the life of the battery.

A fully charged A123 cell will have a voltage of about 3.5v.  During discharge (depending on temperature and current, but generally consistent with the currents drawn by typical portable ham gear) the battery delivers a nearly flat output voltage until the point that about 90-95% of the available capacity has been used.  When that occurs, the cell voltage is about 3v.  After that, the cell voltage literally goes over the cliff rapidly to 2v (based on manufacturer published discharge curves).

So with my 4S A123 packs I have my low voltage cutoff set to 12v (3 volts per series cell).

I have not found definitive data from A123 on “long term storage”.  My assumption is that “long term storage” means just that.  It doesn’t mean if I’m not going to use the battery for a couple of weeks I put it in storage mode.  If I thought I’d have it stored and unused for several months or more, I might.  I have to admit I don’t really know what “long term” means in this context, but I use my batteries at least once a week, so I don’t generally worry about it.

I use a CellPro Multi4 charger, which has a program for putting A123 batteries in storage mode.  It charges the battery to 50% fuel level, which is defined within the charging program as a cell voltage of 3.351v.  Incidentally, the charger also defines the 0% fuel level as 2.99v, consistent with the 3v per cell (12v for a 4S string) as the logical cutoff point, beyond which you’re not going to extract significant energy anyway and, if you’re not careful, risk damaging the battery by over-discharge.

After a day’s use, even if I’ve kept the battery charge up with solar, I put the battery on the charger to balance the cells.  

The specifics may vary with other LeFePO4 battery technologies, but the principles should be similar.


Grant NQ5T
K3 #2091, KX3 #8342




>> I'm always hearing conflicting information about batteries that leaves me baffled.
>
> Contradictions like this are usually resolved by careful study of source documents, not be reading opinions expressed by those who failed to do that, but instead quote the opinions of others who have also failed to do that study. Science is NOT decided by majority vote, nor is it decided by opinion.
>
>  





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[Nr4c]

I believe a fully charged 4S LiPo battery will exceed the max input voltage of a KX3!

Sent from my iPhone
...nr4c. bill

> On Jun 7, 2017, at 3:11 PM, GRANT YOUNGMAN <[hidden email]> wrote:
>
> I think a low voltage cutoff (or at least an alarm) with LiFe is a good idea, especially if you have other devices besides the radio directly connected to the battery, like a KX3, other 12v or USB-powered thingies, etc..  I currently use a Buddipole PowerMini which is a compact battery monitor, low voltage alarm/cutoff, and solar charge controller all in one.  There are other options out there, of course.
>
>
>> On Jun 7, 2017, at 2:40 PM, Bob N3MNT <[hidden email]> wrote:
>>
>> I don't think you have to worry about "C-rating" running a KX3.  You are not
>> drawing 20-80A, but  more like 2-3A.  As for low voltage cut off, you can
>> set that in radio or use an external power /voltage meter to monitor it.  
>>
>
> Grant NQ5T
> K3 #2091, KX3 #8342
>
>
>
> ______________________________________________________________
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[Grant Youngman-2]

A fully charged 4S LiFePO4 battery will be about 14v.  Well within the KX3 limits.


> On Jun 9, 2017, at 8:09 PM, Nr4c <[hidden email]> wrote:
>
> I believe a fully charged 4S LiPo battery will exceed the max input voltage of a KX3!
>
> Sent from my iPhone
> ...nr4c. bill
>
>
>

Grant NQ5T
K3 #2091, KX3 #8342



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[kstover]

It all depends on chemistry.

The "rules" we had for NiCd and NiMH don't apply anymore.
Generalizations about batteries will get people in trouble with Li chem
batteries. If not a fire then possibly a ruined battery pack or worse,
radio.

As an anecdote. I witnessed a HAZMAT training session 15 years ago that
the local fire department put on. It involved an early Li battery, about
the size of a quarter, and a fire in a galvanized steel bucket. When the
Li cell reached the proper temperature, BOOM! The steel bucket ended up
looking like a Mum.

Li chem batteries are much safer now but I still wouldn't put any IN an
expensive radio.



--
R. Kevin Stover    AC0H
FISTS #11993
SKCC #215
NAQCC #3441
ARRL
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[k6dgw]

Bill's observation was for LiPoly.  They're close to 4 V per cell.  3
gave me around 11.7 to 11.8 fully charged, so 4 in series would be near
16 V.  My 4S1P LiFePO4 right off the charger measures 13.8 V, but that
drops to around 12.7 almost immediately after I apply a load.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County


On 6/9/17 5:36 PM, GRANT YOUNGMAN wrote:

> A fully charged 4S LiFePO4 battery will be about 14v.  Well within the KX3 limits.
>
>
>> On Jun 9, 2017, at 8:09 PM, Nr4c <[hidden email]> wrote:
>>
>> I believe a fully charged 4S LiPo battery will exceed the max input voltage of a KX3!
>>
>> Sent from my iPhone
>> ...nr4c. bill
>>
>>
>>
> Grant NQ5T
> K3 #2091, KX3 #8342
>
>
>
> ______________________________________________________________
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