This was a semi-controlled comparison of the alkaline and the NiMH AA batteries with my K1. Now this really only applies to my usage and other situations will be different. Nevertheless I think what I saw is a useful comparison of the two battery types. This test was done with eight cell battery packs.
The first weekend the rig ran about 10 hours on Saturday, about 9 hours on Sunday, and 3 hours on Monday with the 8 NiMH AA batteries Total time was 22 hours and the take was 43 QSOs.
The second weekend the rig ran about 10 hours on Saturday, about 9 hours on Sunday, 5 hours on Monday and 2 hours on Monday with the 8 alkaline batteries. The total time was 26 hours and the take was 22 QSOs.
Data Summery NiMH Alkaline Day 1 10 Hours 10 Hours Day 2 10 Hours 9 Hours Day 3 3 Hours 5 Hours Day 4 0 Hours 3 Hours Total 23 Hours 26 Hours QSOs 43 22 I would conclude that under these conditions neither set of batteries gave a better performance than the other. The alkaline batteries lasted longer for the most part because of fewer QSOs. It was very clear that with just a few more QSOs on Monday the alkaline batteries would have died then and not survived for two more hours on Tuesday. In fact it took the rig an hour in listening mode just to return to the voltages I say at the end of Monday.
But I did draw some useful conclusions. The most significant observation was that the alkaline batteries recovered some of their charge each night they were rested. I even noticed this effect when I had to take a 3 hour break on Sunday afternoon. This did not seem to be as true of the NiMH batteries. So it is clear to me that if the usage is spread out over several days the alkaline batteries have an advantage. On the other had had I been running 3-5 watts instead of 500 mWatts I believe the NiMH batteries would have won this comparison. I will make a comparison at higher power levels another time. And lastly using only 8 batteries put the alkaline batteries at some disadvantage as they could not be fully discharged. Using 10 batteries would have made them look better. On the cost of the batteries the NiMH are a clear winner. Given how many times I can recharge them they are considerably less expensive than a set of alkaline batteries.
At this point I would say if I was going on a several day backpacking trip I'd likely take a 10 cell alkaline battery pack rather than a set of NiMH batteries. However If I'm going to operating in one of the QRP field contest I would do better with a set of NiMH batteries.
One note on using a set of 10 alkaline batteries. As many rigs are rated only to 15 volts and a set of 10 new alkaline batteries can come in at 16 volts, I use a dummy cell till the voltage drops a bit and then I add in the 10th cell. I see no reason to risk damaging the rig.
Let me finish by saying this applies only to using sets of AA batteries. There are other choices out there and I have not tried to make those comparisons.
Test Conditions
First the K1 was set up with just the auto tuner. I had not put the NB in the rig. Plus the autotuner was off line as I was feeding tuned dipoles. I also set the power at my usual 500 mWatts. And lastly I used the speaker rather than headphones. All the QSOs were contest type. The were either getting counties off the county hunter net, playing in the VA QSO party, or in the NJ HB sprint. No rag chewing for these tests and I didn't send CQ for either contest. This was done to keep the comparisons as equal as possible. Wayne of Elecraft has said that the rig is good down to 8 volts. So I declared the batteries dead when they hit 8.0 volts on key-down when running 500 mWatts according to the display on the K1. Receive current drain was about 54 mA, and transmit current drain was about 330 mA. I used an eight cell pack of batteries.