[Elecraft] Internal LiFePo4 for KX3

[Henshaw, Andy]

Well, that's why I had hoped that someone had hacked together a complete solution (including internal charger).  

For my immediate purposes, however, an external charger would be acceptable, even though I hate cracking open my KX3 to remove batteries.  But, for the one- or two-day backpacking trips that I'm likely to do, a single charge would be sufficient for me.

For your last-ditch option (alkaline AAs), I'd imagine that a small bit of circuitry (one 2-pole switch?) would make it relatively easy to convert from two parallel 4-cells batteries (LiFePo4) to one series 8-cell battery (alkaline).


-----Original Message-----
From: Don Wilhelm [mailto:w3fpr at embarqmail.com] 
Sent: Wednesday, February 11, 2015 4:29 PM
To: Henshaw, Andy; Elecraft at mailman.qth.net
Subject: Re: [Elecraft] Internal LiFePo4 for KX3

Andrew,

I must ask - how do you propose to charge them?  The KXBC3 option is designed to charge only NiMH batteries.
I guess you *could* design your own internal charger, but fitting it into the KX3 would be a bit of a challenge.
If you do not design a specific LiFePo4 charger to fit into the KX3, then you will have to remove the batteries to recharge them (and carry along the charger).  IMHO, a PITA.  I would rather run with an external battery pack instead of 'toting' a charger.

So bottom line, unless you want to design your own charger to fit into the KX3 enclosure (and any firmware mods to properly operate and monitor it), then I would think the NiMh batteries or an external battery pack would be the better solution.  That is my opinion.

The KX3 choice of NiMh batteries was a good one.  If the batteries die and there is no source of external power to charge them, one can always find alkaline AA batteries to pop in the KX3 to operate. Things like that do happen in the field and I have not seen fully charged LiFePo4 batteries in the local drugstore yet -- maybe someday, but not now.

73,
Don W3FPR

On 2/11/2015 2:18 PM, Henshaw, Andy wrote:
> Has anyone looked into hacking a replacement battery case for the KX3 that featured LiFePo4 cells?  I've seen external LiFePo4 packs being used, but it seems like an internal solution might be workable.  With a 13.2V supply (four cells in series), one can run the KX3 in full-power mode.  In addition, the discharge curve of LiFePo4 is much better than NiMH.
>
> I'm asking, because I'd like to take my KX3 on some backpacking trips and it just seems wasteful (of space) and slightly awkward (for setup) to have to carry an external battery pack in order to get full-power.
>
> It appears that AA size LiFePo4 cells are available.  So, wouldn't it be feasible to arrange them in a 4S2P configuration that could replace the existing battery holder?
>
>