[Elecraft] Battery requirements for NPOTA activation with KX3/KXPA100

[Esquer Dave]

Hi folks,
I know this has been asked and discussed before but I can’t seem to get a handle on a clear-cut answer …

I am going to do a SSB NPOTA (National Parks on the Air) activation with my KX3/KXPA100/PX3 on battery power. It has been in the works for a while with a special use permit required by the NPS.

How much battery capacity do I need if I want to run full 100 watts? For planning purposes, I am assuming a 6 hour activation with a (highly optimistic I know) 60 QSOs per hour.

The PX3 will be powered by a separate LiFePo 4.8 aH battery, it will do just fine. My concern is the amount of draw I will need to last the 6 hours. With an inline (Hobby King) HK-010 Power Analyzer, I see a max current (KX3/KXPA100 combo) of about 8 amps and about 80 watts during a QSO. The QSOs varies between 50-80 watts on transmit.

I also know that once I am spotted, I can drop the power down to maybe 75-50 watts to save some battery juice.

I have 2 12v-18aH SLA batteries at the ready, am I woefully underpowered? If you have any real-world experience or tips, it is most valuable and appreciated. You can contact me offline at dave dot esquer AT gmail as well.

Thanks,
Dave, K6WDE