KX1 12V Power Mod Update.

[WA3WSJ]

Hello all,

I recently modified my KX1 or should I say my "pimped-out" KX1.
I bought six AA-size Li-ion 3.7V/750mah batteries. I installed them into
each battery holder, but wired the two battery holders in parallel
instead of in series. I now have a 1.5AH internal battery in my KX1. To
ensure all works safely, I also installed a protection pcb. This pcb
monitors the charge current and ensures each cell is properly charged .
It also protects the battery and the radio should a short occur in the
radio. It simply shuts off 12v power to the rig and will not allow power
to the rig until the short is removed.

I tested this by shorting the 12 + and - leads going to the radio. My
KX1 simply turned off and would not turn on. I then removed the short
and turned on the KX1 -- all ok.

On my last AT hike with my KX1 the rig shut off? I had to reset the
protection PCB. After doing so all worked great. Don't know why it shut
down as this was the first time that happened in many trips. Maybe two
hours of sending CQ?

Today I installed a reset switch to reset the protection PCB should this
happen again. I took a dremel tool and cut off a tiny switch on a fuel
gauge PCB I don't use to display the battery charge. The result is a smd
switch already mounted on a PCB about a 1/4" square and about .2" in
height. Perfect for a reset switch in my KX1.

All this is mounted on the bottom battery lid and fits nicely into the
KX1.

I'll soon post pictures of my KX1 reset switch modification on my
website.
http://www.wa3wsj.com/KX1-12vPower.html


72,
Ed,WA3WSJ


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[Mike Morrow-3]

Ed wrote:

>I bought six AA-size Li-ion 3.7V/750mah batteries. I installed them into
>each battery holder, but wired the two battery holders in parallel
>instead of in series.

Ed,

Have you had this arrangement in service long enough to determine that there isn't any significant problem associated with having these two battery banks in parallel?  My experience with such arrangements using other types of cells shows that one bank tends to discharge into the other unless blocking diodes are installed in each bank (which further drops bank output 0.3 to 0.7 vdc).  Does you protection circuit prevent this problem?

I would think that perhaps using a single four-cell holder for 14.8 vdc output might be an alternate approach, especially since the KX1 has a diode in the DC power path from the battery that reduces the voltage applied to the electronics by a few tenths.

Mike / KK5F
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