[Elecraft] Battery power requirements

[Randy Johnson]

I have operated Field Day with my K2 in the QRP mode and one "normal" car battery. No problem.   

I made 460 contacts so calling stations and giving the exchange maybe took 20 seconds. THat means the transmitter was on only on for perhaps 20 seconds per QSO or 8 minutes per hour. Hardly seems like much of a drain. 

I am going to try QRP again, but I am a realistic and it may well be that with conditions as bad as they are today, QRP might be a wasted effort. If it is too frustrating, I'm going to switch to 100 w. That means I will make more contacts that QRP and I would call CQ.  My question is, "Under these circumstances, can I expect the battery to last for the more or less 18 hours that I will be operating?" 

Obviosuly, if not, buying a second battery is a not-very-expensive option.  

Randy W6SJ