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Internal LiFePo4 for KX3

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Henshaw, Andy

Internal LiFePo4 for KX3

Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells? I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable. With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode. In addition, the discharge curve of LiFePo4 is much better than NiMH.

I'm asking, because I'd like to take my KX3 on some backpacking trips and it just seems wasteful (of space) and slightly awkward (for setup) to have to carry an external battery pack in order to get full-power.

It appears that AA size LiFePo4 cells are available. So, wouldn't it be feasible to arrange them in a 4S2P configuration that could replace the existing battery holder?

Andrew Henshaw

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Jim Wilkie

Re: Internal LiFePo4 for KX3

Andt, will wait for the experts to answer, but I think the nimh charger
vs the lopo charger would be a problem.

Jim Wilkie WY4R

On 2/11/2015 2:18 PM, Henshaw, Andy wrote:

> Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells? I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable. With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode. In addition, the discharge curve of LiFePo4 is much better than NiMH.
>
> I'm asking, because I'd like to take my KX3 on some backpacking trips and it just seems wasteful (of space) and slightly awkward (for setup) to have to carry an external battery pack in order to get full-power.
>
> It appears that AA size LiFePo4 cells are available. So, wouldn't it be feasible to arrange them in a 4S2P configuration that could replace the existing battery holder?
>
> Andrew Henshaw
>
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Don Wilhelm-4

Re: Internal LiFePo4 for KX3

In reply to this post by Henshaw, Andy

Andrew,

I must ask - how do you propose to charge them? The KXBC3 option is
designed to charge only NiMH batteries.
I guess you *could* design your own internal charger, but fitting it
into the KX3 would be a bit of a challenge.
If you do not design a specific LiFePo4 charger to fit into the KX3,
then you will have to remove the batteries to recharge them (and carry
along the charger). IMHO, a PITA. I would rather run with an external
battery pack instead of 'toting' a charger.

So bottom line, unless you want to design your own charger to fit into
the KX3 enclosure (and any firmware mods to properly operate and monitor
it), then I would think the NiMh batteries or an external battery pack
would be the better solution. That is my opinion.

The KX3 choice of NiMh batteries was a good one. If the batteries die
and there is no source of external power to charge them, one can always
find alkaline AA batteries to pop in the KX3 to operate. Things like
that do happen in the field and I have not seen fully charged LiFePo4
batteries in the local drugstore yet -- maybe someday, but not now.

73,
Don W3FPR

On 2/11/2015 2:18 PM, Henshaw, Andy wrote:
> Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells? I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable. With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode. In addition, the discharge curve of LiFePo4 is much better than NiMH.
>
> I'm asking, because I'd like to take my KX3 on some backpacking trips and it just seems wasteful (of space) and slightly awkward (for setup) to have to carry an external battery pack in order to get full-power.
>
> It appears that AA size LiFePo4 cells are available. So, wouldn't it be feasible to arrange them in a 4S2P configuration that could replace the existing battery holder?
>
>

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Henshaw, Andy

Re: Internal LiFePo4 for KX3

Well, that's why I had hoped that someone had hacked together a complete solution (including internal charger).

For my immediate purposes, however, an external charger would be acceptable, even though I hate cracking open my KX3 to remove batteries. But, for the one- or two-day backpacking trips that I'm likely to do, a single charge would be sufficient for me.

For your last-ditch option (alkaline AAs), I'd imagine that a small bit of circuitry (one 2-pole switch?) would make it relatively easy to convert from two parallel 4-cells batteries (LiFePo4) to one series 8-cell battery (alkaline).

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Wednesday, February 11, 2015 4:29 PM
To: Henshaw, Andy; [hidden email]
Subject: Re: [Elecraft] Internal LiFePo4 for KX3

Andrew,

I must ask - how do you propose to charge them? The KXBC3 option is designed to charge only NiMH batteries.
I guess you *could* design your own internal charger, but fitting it into the KX3 would be a bit of a challenge.
If you do not design a specific LiFePo4 charger to fit into the KX3, then you will have to remove the batteries to recharge them (and carry along the charger). IMHO, a PITA. I would rather run with an external battery pack instead of 'toting' a charger.

So bottom line, unless you want to design your own charger to fit into the KX3 enclosure (and any firmware mods to properly operate and monitor it), then I would think the NiMh batteries or an external battery pack would be the better solution. That is my opinion.

The KX3 choice of NiMh batteries was a good one. If the batteries die and there is no source of external power to charge them, one can always find alkaline AA batteries to pop in the KX3 to operate. Things like that do happen in the field and I have not seen fully charged LiFePo4 batteries in the local drugstore yet -- maybe someday, but not now.

73,
Don W3FPR

On 2/11/2015 2:18 PM, Henshaw, Andy wrote:
> Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells? I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable. With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode. In addition, the discharge curve of LiFePo4 is much better than NiMH.
>
> I'm asking, because I'd like to take my KX3 on some backpacking trips and it just seems wasteful (of space) and slightly awkward (for setup) to have to carry an external battery pack in order to get full-power.
>
> It appears that AA size LiFePo4 cells are available. So, wouldn't it be feasible to arrange them in a 4S2P configuration that could replace the existing battery holder?
>
>

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Jim Brown-10

Re: Internal LiFePo4 for KX3

On Wed,2/11/2015 2:00 PM, Henshaw, Andy wrote:
> For my immediate purposes, however, an external charger would be acceptable, even though I hate cracking open my KX3 to remove batteries. But, for the one- or two-day backpacking trips that I'm likely to do, a single charge would be sufficient for me.

I've been looking seriously at battery packs for KX3, and agree that
LiFePO4 is the best solution. There are many options at

http://www.batteryspace.com/128vlifepo4batterypacks.aspx

BatterySpace gets their cells from a "partner" manufacturer in China,
combines them in battery packs for all sorts of packages, sizes, shapes,
and ratings, does the marketing, sells suitable chargers, etc. They're
across the Bay from me in Fremont, CA.

There's another company called Bionelle selling 20Ah and 30 Ah batteries
at comparable prices. They come with PowerPole to run the radio, and a
concentric jack for the charger. They're in Southern California. I
don't know anything quality of these products, but both companies offer
quite intelligent support by telephone and/or email.

Carefully note the UN 38.3 Safety Test limitation on shipping. Battery
Space has a lab to do that testing. I think they primarily sell to
manufacturers, but they seem happy to deal with individuals. My
neighbor, W6GJB, had a very good experience with them.

I'm preparing an applications note on portable power, DC power, solar,
etc. and would like to see first hand experience from those who have
used any products in this category, good and bad.

73, Jim K9YC
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wayne burdick

Re: Internal LiFePo4 for KX3

Administrator

In reply to this post by Jim Wilkie

The charger could in theory be redesigned to work with a 12.8-V LiFePo4 pack (4 cells), but there are several disadvantages to this:

- AA LiFePo4 cells appear to have a rating of about 600 mA-hours. As a coarse metric, 4 cells at 13 V would provide about 7.7 watt-hours, which is very poor compared to 8 NiMH cells; the NiMH pack rovides roughly 2500 mA hours at 10 V, or 25 watt-hours. There's room for 8 cells, so NiMH makes better use of the existing space.

- Even though you'd get 13 V from LiFePo4 cells, and could thus run full power, you'd only be able to operate for a third as much time (roughly). The KX3 can put out as much as 5 W from 10 V, and since this is only 3 dB down from full power, it's probably a better trade off for a weekend of casual operation. Your antenna and propagation will generally outweigh this 3 dB power factor.

- Being able to use just about any type of AA cells in a pinch is important for ad-hoc field use of the radio. You can then borrow AA cells from other devices in an emergency. So if you used 4 LiFePo4 cells, you'd want to leave the other socket in place and insert some sort of placeholder cells (easy to lose) or a bypass switch.

- LiFePo4 cells are not as readily available. You can get NiMH cells a drug stores, supermarkets, Radio Shacks [before they close], etc.

Wayne
N6KR

On Feb 11, 2015, at 1:03 PM, Jim Wilkie <[hidden email]> wrote:

> Andt, will wait for the experts to answer, but I think the nimh charger vs the lopo charger would be a problem.
>
> Jim Wilkie WY4R
>
>
> On 2/11/2015 2:18 PM, Henshaw, Andy wrote:
>> Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells? I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable. With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode. In addition, the discharge curve of LiFePo4 is much better than NiMH.
>>
>> I'm asking, because I'd like to take my KX3 on some backpacking trips and it just seems wasteful (of space) and slightly awkward (for setup) to have to carry an external battery pack in order to get full-power.
>>
>> It appears that AA size LiFePo4 cells are available. So, wouldn't it be feasible to arrange them in a 4S2P configuration that could replace the existing battery holder?
>>
>> Andrew Henshaw
>>
>> ______________________________________________________________
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Lynn W. Taylor, WB6UUT

Re: Internal LiFePo4 for KX3

In reply to this post by Henshaw, Andy

I'd be very concerned about "rapid unplanned disassembly" of the
batteries while they were inside the radio.

On 2/11/2015 11:18 AM, Henshaw, Andy wrote:
> Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells? I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable. With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode. In addition, the discharge curve of LiFePo4 is much better than NiMH.
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Jim Brown-10

Re: Internal LiFePo4 for KX3

On Wed,2/11/2015 3:03 PM, Lynn W. Taylor, WB6UUT wrote:
> I'd be very concerned about "rapid unplanned disassembly" of the
> batteries while they were inside the radio.

LiFePO4 cells are far less volatile than Li Ion cells.

73, Jim K9YC
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Henshaw, Andy

Re: Internal LiFePo4 for KX3

In reply to this post by wayne burdick

" AA LiFePo4 cells appear to have a rating of about 600 mA-hours."

I've noticed this also, which seems odd, as my understanding is that LiFePO4 has (at least) comparable energy density as NiMH. However, I did run across these cells:

http://www.aliexpress.com/store/product/High-Capacity-LITELONG-AA-1200mah-14500-3-2v-lifepo4-Rechargeable-Battery-Consumer-Battery-Free-Shipping-4pcs/816574_1302272496.html

which would be better than the NiMH solutions that I've found.

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Wayne Burdick
Sent: Wednesday, February 11, 2015 5:52 PM
To: Jim Wilkie
Cc: [hidden email]
Subject: Re: [Elecraft] Internal LiFePo4 for KX3

The charger could in theory be redesigned to work with a 12.8-V LiFePo4 pack (4 cells), but there are several disadvantages to this:

- AA LiFePo4 cells appear to have a rating of about 600 mA-hours. As a coarse metric, 4 cells at 13 V would provide about 7.7 watt-hours, which is very poor compared to 8 NiMH cells; the NiMH pack rovides roughly 2500 mA hours at 10 V, or 25 watt-hours. There's room for 8 cells, so NiMH makes better use of the existing space.

- Even though you'd get 13 V from LiFePo4 cells, and could thus run full power, you'd only be able to operate for a third as much time (roughly). The KX3 can put out as much as 5 W from 10 V, and since this is only 3 dB down from full power, it's probably a better trade off for a weekend of casual operation. Your antenna and propagation will generally outweigh this 3 dB power factor.

- Being able to use just about any type of AA cells in a pinch is important for ad-hoc field use of the radio. You can then borrow AA cells from other devices in an emergency. So if you used 4 LiFePo4 cells, you'd want to leave the other socket in place and insert some sort of placeholder cells (easy to lose) or a bypass switch.

- LiFePo4 cells are not as readily available. You can get NiMH cells a drug stores, supermarkets, Radio Shacks [before they close], etc.

Wayne
N6KR

On Feb 11, 2015, at 1:03 PM, Jim Wilkie <[hidden email]> wrote:

> Andt, will wait for the experts to answer, but I think the nimh charger vs the lopo charger would be a problem.
>
> Jim Wilkie WY4R
>
>
> On 2/11/2015 2:18 PM, Henshaw, Andy wrote:
>> Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells? I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable. With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode. In addition, the discharge curve of LiFePo4 is much better than NiMH.
>>
>> I'm asking, because I'd like to take my KX3 on some backpacking trips and it just seems wasteful (of space) and slightly awkward (for setup) to have to carry an external battery pack in order to get full-power.
>>
>> It appears that AA size LiFePo4 cells are available. So, wouldn't it be feasible to arrange them in a 4S2P configuration that could replace the existing battery holder?
>>
>> Andrew Henshaw
>>
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Eric Norris-2

Re: Internal LiFePo4 for KX3

In reply to this post by Henshaw, Andy

With batteries, it is easy to let the perfect get in the way of the good (as someone once said). With external LiFePO4 batteries, you can use a roll-up solar panel with a Genasun (or other) solar charge controller (with proper output for this chemistry) and use the KX3 at full power. They are bulky but light. I use a LiFePO4 external pack and the internal NiMH as a backup for my little expeditions, and forget about the charger.

The advantage of external packs is you can mix and match chargers depending on whether you're in a hotel room, backpacking, or at a local park for the afternoon.

Also, the LiFePO4 pack with solar panel and charge controller gets a lot of attention during Field Day, and is a great conversation starter for people "too cool" for radio ("haven't you heard of the internet?"). I'm sure the PX3 will really wow them this year. :-)

73

Eric WD6DBM

Jim Wilkie <[hidden email]> wrote:

>Andt, will wait for the experts to answer, but I think the nimh charger
>vs the lopo charger would be a problem.
>
>Jim Wilkie WY4R
>
>
>On 2/11/2015 2:18 PM, Henshaw, Andy wrote:
>> Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells? I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable. With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode. In addition, the discharge curve of LiFePo4 is much better than NiMH.
>>
>> I'm asking, because I'd like to take my KX3 on some backpacking trips and it just seems wasteful (of space) and slightly awkward (for setup) to have to carry an external battery pack in order to get full-power.
>>
>> It appears that AA size LiFePo4 cells are available. So, wouldn't it be feasible to arrange them in a 4S2P configuration that could replace the existing battery holder?
>>
>> Andrew Henshaw
>>
>> ______________________________________________________________
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>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>>
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Robert Cunnings

Re: Internal LiFePo4 for KX3

In reply to this post by Jim Brown-10

I believe you mean "Bioenno"... I can report that I'm very pleased with
their BP-120 10AH power pack ($190) which I use together with its
companion solar panel ($99). So far so good, runs my K2 nicely, and I've
even used the built-in AC inverter to charge/run a laptop. When running
the inverter was a bit noisy on HF but winding a few turns of the laptop's
power brick AC cord through a type 31 2.4 inch ferrite core took care of
that. A small exhaust fan runs when the inverter is active but it's
quiet. All in all a neatly packaged power pack, even the solar
charge controller is built in. The 12 VDC output is rated at 5A which is
fine for the K2/10.

Specs here:

http://www.bioennopower.com/products/120-watt-hour-power-pack

Bob NW8L

>
> There's another company called Bionelle selling 20Ah and 30 Ah batteries at
> comparable prices. They come with PowerPole to run the radio, and a
> concentric jack for the charger. They're in Southern California. I don't
> know anything quality of these products, but both companies offer quite
> intelligent support by telephone and/or email.
>
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Ignacy

Re: Internal LiFePo4 for KX3

I was thinking about the same in order not to carry the external battery.

The only workable way IMHO would be to:
1. Remove the current battery enclosure
2. Fit 4 polymer Li-Ion , e.g., 2.5A like at the bottom.
3. Connect directly to power inputs, perhaps with a resettable fuse
4. Charge with 2A charger to 15.5-16V (16.8V charger with 1-2 diodes).

I would not bother fitting LiFePO3 internally as they are bigger and store less power.

I did a similar thing with K2, and it toured the world without problems. Great convenience of no extra battery and fast charging.

Ignacy, NO9E

http://www.batteryspace.com/polymer-li-ion-cell-3-7v-2500-mah-875055-2c-9-25wh-5-0a-rate---un38-3-passed-0-75.aspx