SOTA Field Report: How long will Pale Blue Li-Ion rechargeable batteries power the Elecraft KX1?

February and March 2022 were a crazy couple of months for me.

So crazy, that I wasn’t able to fit in one single POTA or SOTA activation for a nearly 4 week period. I’m not sure I’ve ever been that long without an activation since I started POTA in earnest.

Between home projects, wacky weather, timing/logistics, and even a brush with Covid, I had my hands full.

Thankfully, on Friday, March 19, 2022, the stars aligned and I was able to fit in an activation of Bakers Mountain for the Summits On The Air (SOTA) program.

It was so nice hitting the field again!

Pale Blue AA Battery Field Test

I like shaking up my activations and trying new transceiver/antenna pairings. On this particular activation, I had a special test in mind.

A few months ago–almost as an impulse purchase–I ordered a set of eight Pale Blue AA Li-Ion rechargeable batteries. I didn’t check the specifications, but I did watch this somewhat promising assessment on The Tech Prepper YouTube channel.

My hope was that these little Li-Ion cells might power my Elecraft KX1 long enough to complete a field activation.

The KX1 is a marvel of QRP engineering, in my humble opinion, and it was the first super portable transceiver I owned that could be powered by internal batteries.

When the KX1 was first introduced, Elecraft recommended using non-rechargeable Advanced Lithium AA cells from Energizer and Duracell. These batteries sported a rather flat discharge curve and could power the KX1 for quite a while. Of course, the downside is they’re single-use and expensive. Six of those cells would often set me back nearly $9 or $10. Before I started doing POTA and SOTA, I kept a set of advanced lithium cells in my KX1 for casual, impromptu QRP in the field.

Doing frequent field activations–which tend to have much more transmitting time than casual Qs–it’s just not sustainable to purchase these cells, so I tend to power the KX1 with an external battery.

I couldn’t resist the thought that I could use USB rechargeable batteries in the KX1, so I forked out $60 (mild gasp!) for a set of eight AA batteries (these are purchased in packages of 4).

The cool thing about the Pale Blue batteries is that they can be directly charged from any 5V USB power source. Each battery sports a Micro USB port and its own internal battery/charge management system.

I was well aware these batteries would not power the KX1 for hours at a time, but I was hoping they could for at least 30-45 minutes.

The only way to really find out was to do a real-life field test. A SOTA activation would be ideal!

Bakers Mountain (W4C/WP-007)

The last time I activated Bakers Mountain was in 2021. If you’re interested in the history of the mountain and why I think it’s a pretty special SOTA one-pointer, I’d encourage you to read this field report.

I packed all of my radio gear in my Spec-Ops Brand EDC pack and hit the trails at Bakers Mountain Park.

The weather was beautiful and I was in short sleeves for the first time in months!

Temperatures were hovering around 70F/21C and it was breezy along the trails at the base of Bakers Mountain.

As I hiked up to the summit of Bakers Mountain, the wind gusts increased significantly. Evidently, there were strong wind currents just above surface level–not at all surprising for March and April in western North Carolina.

As I approached the true summit (not the observation deck which is well outside the activation zone) I searched for a good spot to set up, avoiding trees with dead branches overhead.

I found a nice spot on the trail that encircles the summit and set up there.

Gear:

It was super easy to launch a line and deploy Steve’s 40 meter end-fed half-wave antenna. I essentially set it up in an inverted vee shape.

I should note here that I include a lot of extra info about my set-up and thoughts about the Pale Blue batteries in my activation video below; please check it out if you’re interested.

On The Air

I was pretty certain those Pale Blue batteries would fail on me at some point, so I had a 12V LiFePo4 battery ready to be hooked up on short notice.

MW0SAW’s EFHW serving up chasers!

I had already scheduled my activation via SOTA Watch, so I started calling CQ SOTA on 20 meters and was auto-spotted using the Reverse Beacon Network.

Using the internal AA batteries, I was pushing a max of 1.5 watts, nonetheless, I was quickly able to validate this SOTA activation with 4 contacts in 6 minutes thanks to W3DDS, WA2JMG, WA1RKS, and AI5DD.

Next, I moved to 40 meters to collect a few more stations.

The SOTA page auto-spotted me on the new band after a few CQs and I logged K8RAT, W5GDW, K8ITU, and K8DRT.

I also logged AC1Z and K2JB (you might remember Dean and Dolly from this field report) as Summit-To-Summit (S2S) contacts. Thanks so much for the S2Ss, chaps!

QSO Map

Here’s the QSO map for this activation. Keep in mind that most of these contacts were made with 1 – 1.5 watts of output power.

Pale Blue AA Battery Field Results

So it turns out the Pale Blue AA batteries lasted about 19 minutes.

I chatted with my buddy Ara (N6ARA) after this activation and we both believe that while the capacity of the batteries is respectable (each cell @ 1500mAh), connected in series they’re producing 9V which is close to the 8V minimum supply voltage of the KX1.

As Ara pointed out, these Pale Blue batteries are likely geared for lower-current/large-capacity applications. With a higher internal resistance–with current demands on transmit–the output voltage of the battery combo drops significantly.

These batteries are so lightweight, I believe I will keep them in the KX1 as a backup only and try not to use them for longer than 15 minutes. That’s enough time to complete a typical SOTA activation in a pinch.

If you have a better solution for a KX1 internal rechargeable battery setup, I’m all ears! The big limiting factor is the real estate inside the KX1 chassis–one part of the KX1 board divides the usable area in two.

Activation video

Here’s my real-time, real-life video of the entire activation. If you’ve been looking for a good insomnia cure, you’ve found it!

Click here to view on YouTube.

One thing you’ll notice in the video: near the end–shortly after I plugged in the 12V battery–my output power dropped significantly according to the KX1 internal power meter. I’m not entirely sure why this happened.

Since this activation, I performed two more activations and did notice the power output diminishing after about 20-25 minutes on the air.

I’ve yet to test the little rig in the shack on my variable power supply, watt meter, and dummy load to see if the power is, indeed, diminishing or if it’s just the KX1 power meter reading. I certainly want to sort this out!

Thank you!

It was so incredibly nice to hit the field, the trails, and the airwaves once again! Thank you for reading this report.

As always, I’d like to send a special thanks to those of you who have been supporting the site and channel through Patreon and the Coffee Fund. While certainly not a requirement as my content will always be free, I really appreciate the support. It makes videos and reports like this one possible.

Here’s wishing y’all good health and good propagation!

Cheers & 72,

Thomas (K4SWL)

9 thoughts on “SOTA Field Report: How long will Pale Blue Li-Ion rechargeable batteries power the Elecraft KX1?”

  1. I bought three different brands of AA lithium rechargeables.

    I put a set into a camera flashgun and they got so hot, the plastic wrapping melted off!

    I have not tried them in any radio gear as yet, but I am curious how much radio interference the buck-converter inside each battery creates.

    One of the battery sets I bought came a USB ‘c’ charging tray. None of them are marked with anything useful to explain what their capacity is. The ones with the micro-usb socket seem to be the only ones to dramatically overheat….SO FAR.

  2. 19 minutes! That’s… not great.

    Your hypothesis regarding dropping below 8V sounds likely. I haven’t seen a discharge curve for these batteries.

    Are they even really 1.5V fully charged?

    73,
    Bob

  3. Thomas very interesting. Thanks.
    I’m heading up your way or close on Thursday ish.
    We are coming up 441 or 23/74 heading back to VA. Am at a conference in Roswell GA .

    Yes I brought my KX2. So am thinking of stopping and doing a ‘quick’ POTA, somewhere along the way.

    73
    Fr Richard
    Wb8yxf

  4. Fyi, 14500 lithium polymer cells are the same physical size as AA cells, and if you re-wired the housing to be 3 in series by 2 parallel (3s2p, instead of all series), you would have a pack that runs from 12.6v fully charged, to 9v fully discharged (there would be almost zero voltage sag during transmit, and you would be well above 10v for almost the whole discharge curve). And you would have about 1400-2000mAh of capacity, which should last 4 or more hours of 50% transmit duty cycle.

    There are also some cells with built-in protections. The main one to look for would be over-discharge protection. Otherwise you would have to be sure to manually turn the radio off before you hit 9v to protect the cells from permanent damage. I would simply remove the cells and use a dedicated charger for charging, so that they stay balanced (if you charge them in that housing without a BMS, they may eventually get out of balance).

    Note that all of your problems are not because of the chemistry of these “AA” cells, but the limitations of the circuitry inside that drops the cell voltage from 3.4 to 1.5v -which really isn’t necessary for a radio that wants 12v.

  5. what about adapting a laptop battery (plus a minimal voltage regulator) to the KX1 ?

    Removing the battery holders there may be enough room for the battery, which may be hold in place with a pair of elastic bands or something like that; such a batter would last really long given the limited power drawn by the KX1

  6. Thomas, as always, an enjoyable video!

    This is off topic, but can you share the link where you acquired that operating clipboard? Or if you printed it, can you share the files? I’ve been looking for something exactly like it but have been unable to source one. Thank you.
    Rich
    KQ9L

  7. Hello Thomas.
    Today I just activate a sota summit in YO with my KX3 with eneloop pro AA batteries. The power used was 5W. I made around 14 contacts 20-30 mins (after that I had to live the summit due rain). After that, I tried to activate a WWFF parck (without success due broken coaxial…that I observed one hour and 20 mins later. The first low battery warning was after 1 hour and 40 mins of operation
    So, KX1 should work better with AA Eneloop Pro (KX3 cosume around 200mA on RX and 2.1A on TX with 5W. KX1 is consume around 80mA on RX…and around 1A…true…on 2W.
    Also I made some tests with KX3: I am able to send CQ for around 2 hours with AA Eneloop Pro.
    True, the batteries are relatively new.
    I think that from now, I will go on sota activation just with AA batteries (I will keep my LiPo Battery at home for WWFF activations)

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