AA Cells in Various Chemistries

AA batteries are available everywhere. They’re cheap, convenient to use and are available in a variety of chemistries: rechargeable NiCad and NiMH; non-rechargeable alkaline and lithium. NiCads are essentially obsolete now that NiMH’s are on the scene with more capacity and less weight. So the relevent characteristics of the other three types, each with their own advantages and disadvantages, are shown here graphically.

aa various

The Energizer e2 Lithium batteries pack a mean, but expensive punch. The 8-cell pack represented here cost $24 and they are non-rechargeable! They are lighter than normal AA alkalines and maintain their voltage under load more consistently than alkalines. But their expense renders them unsuitable for QRP (at least at my QTH!).

The capacity of rechargeable NiMH in AA-size has incresed in resent years and are now available in advertised capacities of 2500 mAh. Shown here are two smaller capacity sizes of 8-cell packs of these batteries. An 8-pack of the 2500 mAh batteries costs around $20 making these batteries the best choice for those needing standard sized batteries in their K1′s, KX1′s or external standard-sized battery housing. They are advertised as having over 100 recharge cycles. NiMH cells have a nominal voltage of 1.2V compared to 1.5V for alkalines so users of these batteries may wish to use a 10-cell pack.

Alkaline batteries were my favorites for a long time. This was mainly due to their convenience – I could buy a fully chraged, ready to go set on my way to an outdoor event and not worry about memory effect or whether or not I fully charged them the night before. I knew that their voltage decreased almost immediately after applying a load – what I didn’t know was how steep this decrease was. I no longer use alkaline batteries for QRP.

Effects of Temperature on Alkaline AA Batteries

I knew that temperature had an effect on battery output but was surprised and interested to learn the degree (no pun intended) to which it affected battery life.

TempTime

Name Brand vs. Off-Brand – 8 Non-rechargeable Lithium AA’s

Steve KA9QOA recently posted a source for lower priced generic lithium AA cells to the Elecraft mailing list. The source was BatterySpace.com and the batteries cost half the price of the Energizers. Wondering if the old adage “you get watch you pay for” holds true in this case, I ordered a set & compared them with the more expensive Energizers.

The graph below represents an 8-pack of each brand and shows that the generic batteries last about 90% as long and provide about half a volt less output throughout their discharge curve as the Energizers. But at half the price, this seems reasonable to me.

2 lithium AAs