Elecraft KX2 battery source

I collected my KX2 today and so far I am delighted with it.

Has anyone in the UK found a source for the internal 11.1 volt Lipo battery?

Terry G4POP

Hi Terry

I got a replacement for mine from Waters and Stanton. It cost me about ÂŁ35 and took 3 weeks to be delivered from Elecraft in the states. I struggled to find another source.


Nick G0HFL

The battery for the KX2 was designed for the radio by a company in Silicon Valley. I don’t know of any other source for it. If you order the battery from Elecraft you should also order the charger that is used to charge it from them. Elecraft doesn’t recommend charging the battery by any other means than the charger made for it.

Gary A. - W0MNA

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If applicable maybe 3 samsung 18650 cells, you can find in most laptop battery for example, 73 CT2IUV

Tenergy Li-Ion 18650 11.1V 2200mAh Rechargeable Battery Pack with PCB Protection

Can be purchased from Amazon. Add your own connector. Should fit and work.
$26.99 USD. The battery in the KX2 is also a Tenergy
Don, NK6A
Waiting for my KX2.

This here available at conrad.com looks similar:



Not used LiIon cells so far, just wondering a bit about the different charging recs:

  • Tenergy recommends 0.2C Standard and 0.5C Rapid charge
  • Samsung recommends 0.5C Standard and 1C Rapid charge

Is 0.5C common practice for LiIon cells?

OK the best source for this battery is from Robotshop who have a European distribution ceter.

Cost was ÂŁ25.14 including carriage and VAT and its a Tenergy unit


73 and thanks to the guy that suggested the Tenergy unit as it would appear to be the only one of the correct physical size to fit the battery compartment.

Terry G4POP

Thanks for this. I’ve just found out (after waiting 2 weeks for a delivery that never materialised) that USPS won’t carry these batteries. (Pity they didn’t tell anyone :rage:) Rather than pay over 100USD for UPS I opted to just get the radio without. So delivery back on track, I hope. Do you know what connectors I’ll need?

Hi guys,

Is there any real, practical, advantage to having the battery inside the radio? Several reasons for asking, among which, Elecraft will not cover battery-leakage damage under guarantee (at least not on the K2, K1 or KX3, presume same for KX2), and all it does is lessen your choices of battery cost/capacity/charging choice, etc…

It seems safer, cheaper and more convenient (to me) to run from an external battery, and that’s what I do with my K1, K2 and KX3. My K2 came with an internal battery, but I took it out very quickly, it runs fine (better, lighter…) with modern batteries and I retain that choice to upgrade as needed by using the external power source.

Of course the K2 internal was a SLAB, and I’m glad not to be there any more!

Ditto, of course, on the MTR.



For me it’s just the convenience of no having to carry an extra item, with the internal battery I can fit the complete station inside the Lowepro CS 60 bag including wire antenna and counterpoise. Of course the fishing pole if required is an extra Hi

The battery needs to be removed for charging so it’s only installed before a trip therefore the likelihood of leakage damage is low, my guess is that that’s the reason Elecraft did not make it possible to charge it in situ.

You can use an external battery whilst the internal battery is installed and the Tranciever will use whichever battery has the highest charge.

The KX2 is super flexible and fits every users requirements, it’s up to you!

73 Terry G4POP
Log4OM Development Team

Hmm. USPS just delivered mine. Clearly marked on the outside of the package what was inside.

Interesting. I got one yesterday. They actually held up my order because I picked USPS until I paid the extra $6 for UPS because they couldn’t ship via USPS.

I ordered lipos from Hobbyking which were shipped from Hong Kong via UPS Hazardous. That means, as far as I am aware, they came via airfreight rather than on a passenger service. Exactly why Elecraft cannot ship via UPS Hazardous I do not know. Can someone enlighten us, or at least me, here?

Mysterious. My package had a label stating, “Lithium-Ion battery inside. Do not load or transport if damaged.” Elecraft even refunded a significant portion of my shipping fee because the postage was much less via USPS than UPS (as calculated by their website). The KX2 and battery came via Priority Mail. It was their Christmas promotional special.

UK Postal Service will still carry Lithium batteries under fixed conditions. These including limits on the Lithium content or the WH value, whether the battery is in its original container, whether it is installed in electronics, packed and boxed so it cannot be activated etc.

So you can ship a radio in its original packing with a LiION battery with relative ease.


For about one year I have been using these battery packs from Xpresstek in my KX2:


These packs contain three Panasonic 18650 cells rated at 3400 mAH. The pack also contains a protection circuit PCB. The pack is rated at 38 WH and weighs 150g - this is quite incredible! It fits the KX2 just as well as the recommended battery. The only issue is that you must add your own DC connector, not for the faint of heart or those with unsteady hands - but the protection circuit probably would avoid disaster, in case of a short.

These batteries appear to be available at a reasonable price:


Just go to the search box and put in LI_111_3400.

I charge these packs with a homebrew 12.50V regulated supply. The voltage is regulated by a linear regulator, with 20T precision pot, screwdriver adjusted. The current is limited to 1.0A maximum by an active current regulator. This has served me safely for hundreds of charges of these and other lithium 18650 cells. This is a very conservative charger for these packs.

Xpresstek has all the specs you need to decide if other chargers are appropriate, and they may be able to recommend a charger as well.

I also have the Elecraft-recommended Tenergy battery, and it is just fine, except that the batteries from Xpresstek last longer in the radio. The Tenergy charger is more aggressive, causing the Tenergy packs to warm slightly during charge, while my homebrew regulator is more gentle, with no obvious warming of the cells. I don’t recommend using the Tenergy charger with the LI_111_3400 battery - play it safe - if you use that charger, add a series resistor to limit the current to about 1.0A.

I realize that this information goes sideways to Elecraft’s strict words about using only their approved internal battery. They have every reason to warn their customers, because using an inferior battery, or using any battery incorrectly, might cause a tragic event.

I know of two other SOTA ops who are also using these same 3400 mAH batteries in KX2’s with happy results. However, you use any lithium battery at your own risk, and using the battery external to the radio probably reduces most of the risks to the radio.

Be aware that the KX2, with its black finish, can get very hot sitting in the sun. I have had mine protect itself once due to solar overheating! Lithium ion batteries can fail at high temperatures, so remember to keep your KX2 or KX3 in the shade - even when off.

I’ve done about 220 activations in the past year, and on almost every activation, I have run my KX2 at the full 10 watts output, for the entire time, using these 3400 mAH batteries. Generally I have no problem doing two or more very long CW activations - about 50 contacts each, + or -, and I still have not dropped below 10W output.

Please note that these batteries do not have enough voltage to allow the KX2 to reach an output of 12W with the new firmware. A higher voltage battery is needed. However, four series lithium ion cells, fully charged, have too high a voltage for the 15V max of the KX2.

Please follow Elecraft’s recommendations about internal batteries, unless you have the required knowledge to use a different battery, charge it properly, etc. I provide this information for those who might want an alternative, and who understand the risks.

Xpresstek ships their batteries to the 48 states with no hassles - please contact them if you have questions.



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Thanks George. This is super helpful.

Here’s some other info too:


UK supplier: https://www.robotshop.com/uk/111v-li-ion-2200mah-bare-battery-pack.html

If you don’t want to roll your own, this guy will put a connector on for you :wink:

The one that KX0R listed looks the best for pwr/$$. I also saw last summer at Salmoncon a couple of KX2’s modified with internal charging circuits. Not sure if they were going to be marketed or not though…Haven’t seen anything else on it since then…

73, Todd KH2TJ

It might be something to do with the difference between international and domestic transport Larry.

Yeah, my first thought too. But then N0MAP said couldn’t get his delivered by USPS. Maybe new rules for 2018? It was noted (on the inside of the package) that the battery had not been charged in excess of 20% of its capacity. Mine was delivered in the last week on 2017.