[Elecraft] KX1 on AAAs or Lithium Polymer?

[Alan WB6ZQZ]

Lithium Polymer and Lithium Ion batteries are used in many millions of 
cellphones, cameras, PDAs, laptops, etc., etc. every day. These batteries 
MUST NOT be OVERCHARGED or OVERDISCHARGED. The proper charger will solve 
this problem, and protection circuits also can even prevent overdischarge 
by disconnecting the load. These circuits are common in industry with these 
batteries.

Laptop, PDA, camera and cellphone batteries last a lot more than one year, 
as an example. Life expectancy is more like 3 years or better. It depends 
on many factors including the number of charge/discharge cycles.

Lithium chemistry batteries have very low self-discharge. If disconnected 
from any loads they typically maintain most of their charge over many 
years. For this reason they are far superior to other rechargeable 
technologies when it comes to 'readiness' after sitting in storage. They 
can also be maintained in standby charging mode, which often tends to kill 
other battery technologies.

I put a set of LiPo batteries into my K2 over a year ago and they are still 
charged and operating even though I've ignored them for almost a year. I 
have not used them a great deal, but they do hold their charge very well if 
disconnected. I always make sure I turn off the battery disconnect switch 
at the rear of the K2 when shutting it down. Details of my installation 
follow at the link below.

http://www.qsl.net/wb6zqz/k2/lipo_batteries.html

One day I had a discussion with Wayne (of Elecraft) regarding LiPo 
batteries, and I don't expect to see anything like that from Elecraft 
anytime soon.

The safest way to deal with Lithium Polymer batteries is to have a 
protection circuit packaged with the battery pack. This circuit prevents 
over and undercharging. These circuits are commercially available. They use 
low-loss FETs rather than diodes. Make sure they allow the high current 
drain required for your application.

-- Alan wb6zqz


At 07:06 PM 11/26/2005, Fred Jensen wrote:
>One Ham's Experience:  Good News: The LiPoly I got (local RC hobby shop) 
>was just great!  I did not deplete it on our cruise thru the Panama Canal, 
>maybe 6 hours operating time (mostly listening and no CQ's), but I did rag 
>chew a bit with a number of SA stns.  Ran a Spartan Sprint after return 
>without recharging just to see if I could.  Voltage stayed nearly constant 
>until full discharge, at which point it dropped quickly.  As quickly, I 
>recharged it on a MAHA 77.
>
>Bad News: It worked again very well in the next Spartan.  Then I got busy, 
>and didn't check it for perhaps 5 months.  At N6A (Alpine County, CQP), I 
>tried it our before the contest, and it was toast.  They are extremely 
>light (a factor in Spartan, but I wonder in a back pack), they seem good, 
>but they are expensive, and I've heard they die in a year or so, 
>regardless of how you use them.
>
>WAYNE:  To your basic questions -- I wouldn't spend much (or any) time 
>adapting the KX1 to LiPo.  Mine came with tinned leads on which I put a 
>coax plug.  The expense is a real downer.  The difference in power between 
>6 and 8 AA NiMH's seems minimal.  Yes, Alkaline dry cells do have a 
>non-flat discharge curve, but you can get an bunch of them at Costco or 
>Sam's and they're what I generally use.  I think the weight of the 
>additional batteries is overshadowed by the weight of the solar panel and 
>regulator for those who really do back-pack (I did but I don't anymore -- 
>too old).