Homemade Battery Packs for KX-2/KH-1

Operating KX-1 on Field Day 2007 

The bane of operating portable is running out of battery power before you are ready to QRT and close the station.  Now that I am using the KX-2 as my primary out and about radio, I needed to find a way to supplement the battery situation.  I have two of the batteries that Elecraft sells, and they are about 3 or 4 years old and they work fine, but I thought I might start looking for some spares.  

Being a frugal (aka tighfisted) ham, I was deterred when I saw the pricing for brand new Elecraft batteries.  

Now I am certain they are worth every penny, as Elecraft makes nothing but good goods in my experience with them over the years.  My ham brain just insisted I dig deeper and see if I could cobble some battery packs up on my own.  This is what I came up with. 

The battery pack that is used in the KX-2 and the KH-1 is a pack made from three Lithium Ion cells, commonly known as 18650's.  If you have an EV, you probably own a thousand of them and maybe did not know it. 

The Lithium Ion cell is not to be confused with the Lithium Iron Phosphate batteries.  The Lithium Ion batteries used by the KX-2 and KH-1 are not smart batteries.  They have no built in battery management chip (BMS), so you CAN overcharge them, and they CAN catch fire. 

I found these battery packs on Amazon.  They were marked about $32 for the pair. I think they are $39 now so keep an eye out. 

https://www.amazon.com/dp/B0BJ5QJ2GS

The power connector for the KX-2 and KH-1 is a male DC plug, 5.5mm by 2.1mm in size.  So I bought a bag of plugs, snipped off the 2 pin connectors on the batteries and soldered on the DC plugs. 

https://www.amazon.com/dp/B083J24LTZ

You need to do some thinking ahead on this.  I used a piece of shrink tube on each of the two connections, and then I used a bigger piece of shrink tube to cover the connections and help to support the connection at the plug.  Harbor Freight sells a fantastic little heat gun that is perfect for shrinking shrink tube, shrink wrap or softening hot glue.  It runs about ten bucks. 

Super Cheap Harbor Freight heat gun

So basically for less than fifty dollars I was able to make two spare battery packs.  I charge them with the Elecraft Tenergy Lithium Ion charger that I bought with the KX-2.  Any smart charger that is acceptable for use with Lithium Ion batteries will work.  Never leave Lithium Ion batteries on the charger unattended.  They ARE a fire hazard. 

Still cold here this week...we're promised temperatures in the 60F-70F range next week.  Fingers crossed.  Looking forward to getting back out in the parks and operating. 

On another note these batteries run my K1, K2, KX-2, and Hilltopper rig very well, apparently they all accept the 5.5mm by 2.1mm DC power plug.  Nice. 

73 de KB9BVN

Brian