[Elecraft] [K2] LiFePO4 replacement for internal SLA battery in K2

[Fred Jensen]

On 9/13/2015 3:23 AM, Bill W4ZV wrote:

> I understand and agree for your use case of mounting the battery internally
> in the K2.  My "fail safe" is to never use an internal battery and thus
> avoid issues of fire, leakage, etc.  I always charge and mount my LiPOs
> externally.  It's certainly possible to abuse LiPOs and cause them to catch
> on fire, but as you stated, there are plenty of devices that successfully
> use them internally...significantly more than LiFePO4s when you consider the
> volumes of cell phones, tablets, PCs, models, drones, etc. that use LiPOs.
>
FWIW: I had a small 900 mAh LiPoly about the size of a small match box 
catch fire while using it to power my KX1.  I got it at the local RC 
store.  It was external on a short pigtail, I was on the deck with my 
AlexLoop, and I was able to yank it from the KX1 and fling it over the 
rail down onto the gravel driveway.  The pyrotechnic display continued 
for about 4 min.  Really glad I wasn't in the house.

> Just an FYI for anyone interested, the "11.1V 4500mAh 3S 30C Lipo" listed on
> a popular auction site for $24.36 is actually available for $20 if you use
> "Make Offer" (I just bought one).  Of course you also need a balancing
> charger (available for around $20) to properly charge and store LiPOs.  You
> cannot beat the energy density (mAH per ounce) of a LiPO but they DO REQUIRE
> proper care.

I've had poor results from the couple of batteries I bought off a well 
known auction site.  One was billed as a 9 Ah LiFePO4 and the other as a 
4.5 Ah LiPoly.  Both exhibited a linear, downward discharge curve and my 
K2 quit fairly quickly on low voltage.  When I recharged it, the "9 Ah" 
one took 1,300 mAh which, to a first approximation, is about the usable 
capacity I got from it.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org