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KX3 won't go above 10W

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Fred Soop

KX3 won't go above 10W

I have looked at the power issue (even though I'm not yet a KX3 owner) and with NiMH cells at 1.2 V, the 8 cell internal battery holder would only be 9.6 V. I'm considering an external battery pack with (2) 6 cell holders for 12 cells total. That would be 14.4 V total. A single series diode would bring that down to 13.7 V. The NiMH cells do start at 1.5 V with full charge for a short time, so some additional series diodes would be needed with a fresh charge and could be switched out as the cell voltage drops to 1.2 V. A voltmeter and rotary switch with 5 diodes would do the job.

73
Fred Soop AC9RQ

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Mark Goldberg

Re: KX3 won't go above 10W

Go with LiFePO4 cells. Four cells will keep the voltage between 12 and 14.4
V from 10% to 100% state of charge and most of the time the voltage is
between 13 and 13.5 V. I use small ones (3 AH )for backpack portable
operation, 20 AH for fixed portable and my RV has 400 Ah to run the rig
forever! The KX3 stays at the max 15W almost all of the time. No fuss, just
works, and they keep their charge for months. Small ones start at about $50.

Regards,

Mark

On Mon, Jun 24, 2019 at 12:40 PM Fred Soop <[hidden email]> wrote:

> I have looked at the power issue (even though I'm not yet a KX3 owner) and
> with NiMH cells at 1.2 V, the 8 cell internal battery holder would only be
> 9.6 V. I'm considering an external battery pack with (2) 6 cell holders for
> 12 cells total. That would be 14.4 V total. A single series diode would
> bring that down to 13.7 V. The NiMH cells do start at 1.5 V with full
> charge for a short time, so some additional series diodes would be needed
> with a fresh charge and could be switched out as the cell voltage drops to
> 1.2 V. A voltmeter and rotary switch with 5 diodes would do the job.
>
> 73
> Fred Soop AC9RQ
>
> ______________________________________________________________
> Elecraft mailing list
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>

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Jim Brown-10

Re: KX3 won't go above 10W

On 6/24/2019 12:59 PM, Mark Goldberg wrote:
> Go with LiFePO4 cells

Yes. This ham-friendly company sells a wide range of LiFePO4 batteries.
Charge before you leave home (all Li batteries require a charger
designed for their specific chemistry, voltage, and capacity), connect
to your KX2/3 external power jack. Choose the capacity/weight that suits
your planned use.

$50 will get you 3Ah that weighs 13 oz; add $15 for the charger. A 6Ah
battery goes for $80, approximately twice the weight. I paid about $195
for a 20Ah battery that weighs 5.4#, +$20 for a faster charger.

https://www.bioennopower.com/collections/12v-series-lifepo4-batteries

73, Jim K9YC

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Chris Waldrup-2

Re: KX3 won't go above 10W

Thank you.
Gigaparts is local to me and I see they have the Bioennos in stock!!

Chris

> On Jun 24, 2019, at 4:35 PM, Jim Brown <[hidden email]> wrote:
>
>> On 6/24/2019 12:59 PM, Mark Goldberg wrote:
>> Go with LiFePO4 cells
>
> Yes. This ham-friendly company sells a wide range of LiFePO4 batteries. Charge before you leave home (all Li batteries require a charger designed for their specific chemistry, voltage, and capacity), connect to your KX2/3 external power jack. Choose the capacity/weight that suits your planned use.
>
> $50 will get you 3Ah that weighs 13 oz; add $15 for the charger. A 6Ah battery goes for $80, approximately twice the weight. I paid about $195 for a 20Ah battery that weighs 5.4#, +$20 for a faster charger.
>
> https://www.bioennopower.com/collections/12v-series-lifepo4-batteries
>
> 73, Jim K9YC
>
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