[Elecraft] LiFePO4 battery packs

[Fred Jensen]

On 7/6/2012 7:06 PM, Steve Jackson wrote:

> So, what is the opinion of the learned and experienced regarding these
> battery packs?

Well, there's the obvious ... 600mAh vs 3,000mAh of course.  The LiFePO4 
batteries have a very good capacity to weight ratio, and they are safe, 
you can carry or pack them onto airplanes.  Neither one of them allow 
you to balance the cells however, something that should be done at least 
periodically.

Assuming it is for your K2, you'd probably find that 600mAh was a little 
small.  My K2 draws about 280mA on receive, and at 5W, around 1.5A key 
down.  I use a 4Ah 4S1P LiFePO4 pack that I can balance the cells on 
charge and it lasts about as long as I want to be off in the field 
somewhere.

Li-Poly batteries have a higher capacity to weight ratio which is why 
they are used by RC model folks.  I have one that's about the size of a 
small matchbox, weighs an ounce or so, and is rated at 800mAh, 11.7V.  I 
use it on my KX1.  Li-Poly is somewhat unstable under some circumstances 
and I've had one catch fire while I was using it.  Mine is on a short 
pigtail outside of the rig.

> What's the better deal?  Two of the former?  Anything awful about these
> packs?  Caveats in their use, other than the obvious?

A123 cells are probably the highest quality, Buddipole sells them, they 
are a bit pricey however.  Whatever you choose, be sure to fuse the 
cable to the rig.  These chemistries can deliver anywhere from 10C to 
15C or more if shorted.  For mine, that could be more than 60A.  Beware, 
the 12V and RF connectors on the RF board are the same and the cables 
from the KAT2 will interchange quite easily.  I speak from experience 
and now have a jumpered trace on the board that decided to be a fuse. :-(

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2012 Cal QSO Party 6-7 Oct 2012
- www.cqp.org