L91 & L92 discharge characteristics

Batteries and Chargers Consumable Batteries
1

I’ve been noticing odd discharge characteristics in L91s and L92s lately.

I just changed out an L92 in a 1-aaa light that was ‘dead’ and out of curiosity, tested it. It still showed 1.46v. I stuck it in a different light, and sure enough, it wouldn’t deliver any power. Shouldn’t 1.46 volts still deliver something? A NimH cell at 1.2v works just fine and continues to work well below that.

I’ve also noticed L91s in my 2-AA lights starting to perform as ‘dead’, and when tested, would find one cell at 0.9v and the other at 1.5 or 1.6v. I’ve tossed the low reading cell, and was able to run the remaining cell in a 1-AA light for quite some time. Shouldn’t they discharge more evenly than that? And yes, I always put in matched fresh pairs.

Do lithium primaries have some odd habits that I’m not aware of? I prefer them in lights that have value, as I’ve had too many ruined by alkalines - and I appreciate the lighter weight, especially in things like the Preon 2 that lives in my shirt pocket, but the unusual discharge readings have me puzzled.

2

Probably very high internal resistance. The batteries show up as just fine when they are actually dead, something like phantom voltage. (Not XLR)

Short the cells out with your multimeter in current mode. I’m guessing they will read very close to zero.

3

Test them under a load: somewhere between a 1 and 10 ohm resistor will work.

4

Per the technical PDF downloadable from Energizer the discharge curve on the Ultimate Lithium cells is almost square. Holds voltage almost steady until the battery is almost fully discharged and then the output drops like it fell off of a cliff. Very different discharge curve than either Alkaline or Lithium Ion cells. Closer to NiMH cells which also have a sudden death curve when fully discharged, but a bit less extreme than the L91 and L92 batteries.

If you are curious both Energizer and Duracell have technical specifications PDFs downloadable for many of their batteries which include lots of good information including temperature versus performance info. Good to know for winter use of batteries.

5

This depends on the load, a high load does spoil the square shape a bit.

From my review:

6

HKJ;

None the less what other non rechargeable AA or AAA cell comes close to providing the current that the L91 and L92 cells can? Up to 1 Amp continuous discharge they show little decrease in overall capacity. The best NiMH batteries (Eneloops) may do better at the highest current draw levels but some electronics wants the higher voltage. Also the Energizer batteries are about the best at very cold temperatures. Living in Denmark as you do I am sure that you have some familiarity with those.

7

There are other options for higher voltage than Enegizer, how good they are can be discussed.

Denmark is not that cold! We have a few days during winter below 0C and at the current time we have it very hot, i.e. above 25C during the day.

8

HKJ;

In Reno we have summer temperatures that can reach 40C+ and in winter I have seen it get close to –30C, though rarely and we are only at 40 degrees North. I am at an altitude close to 1500 meters and 300+ Km from the ocean with the Sierra Nevada mountains between Reno and the ocean. You have the Gulf Stream helping moderate the climate in Copenhagen I believe. How is inland Denmark’s climate in the winter?

I realize there are numerous sizes of Lithium Ion rechargeable batteries and 3V lithium non rechargeable batteries available but most devices designed for AA or AAA batteries cannot use them. As an AA or AAA alkaline direct replacement we are limited to either NiMH or Energizer 1.5V nominal Ultimate Lithiums or similar chemistry batteries so far as I know. The other 1.5V lithiums seem to be pretty rare batteries at least in the U.S.

Not too sure about the situation in Europe but it is still impossible to walk into an average store and buy cylindrical bare Lithium Ion rechargeable batteries here except possibly if there is a ecig vaporizer store locally. As a non smoker I am not sure. In retail stores the selection is limited to alkaline, NiMh rechargeable and Ultimate Lithium batteries and in sizes above AA the NiMH batteries are the minimal capacity versions with capacities about 3000 mAh for both C and D size cells. CR123 and CR2 non rechargeable 3V Lithium batteries may be in the photo supplies section too but they are expensive compared to internet prices. Lots of battery options exist but only on the internet for most people.

Not arguing so much as pointing out that for the average battery consumer the choices are pretty limited without considerable investigation and self education. Otherwise the alkaline battery would be dead.

9

Denmark is to small to have inland climate, the maximum distance to the ocean is probably around 70km. Winter is mostly around 0C, we do frequently see down to -10C and seldom -20C, the cold record is about -30C.

Mostly we buy special batteries on the internet in Denmark, shops does not have a very large selection and it is mostly Alkaline.

I do have a rather interesting replacement for AA in queue for testing.