Lithium vs. Alkaline

[jbrett14]

OK, I am a bit puzzled. If a battery-powered device (flashlight, camera, etc.) runs on AA Alkaline batteries, shouldn't it also run on Lithiums? I have a SL 4AA 7LED Poly light in which many have said, including SL: Do not use Lithiums because of higher voltage. This is where I am puzzled. Why would the battery industry not use the same voltage throughout a fixed size of battery? E.G. All AA batteries would have the same voltage & therefore be usable in any device that takes AA. I mean, if they are going to use a different voltage, then why not make it a different size battery to avoid confusion? As a rule of thumb what devices can use the Lithiums (AA or AAA)?

 

[IlluminatingBikr]

AFAIK, the companies don't really "pick" the voltage. It has to do with the inners of the cells, and how the chemicals react and all that.

I can't give you a technical answer, but I know that it is because of how the battery works....and is not a choice or something the manufacturer gets to play with.

 

[Empath]

The voltage of a cell is determined by the chemistry. Even if the lithium was the same voltage as the alkaline, there would still be a problem. Equipment is designed expecting a cell to perform in a certain manner. If alkaline is considered, the voltage drop under load (internal resistance) is considered in the equipment design. If a lithium was used, the voltage drop wouldn't be as expected, so the circuit would be receiving a higher voltage for a longer period of time than desirable. That's not important in every application, but some circuits are less forgiving than others.

 

[jbrett14]

So, I guess in short: We can send a man to the moon, but we can't control the voltage of a battery.

 

[jbrett14]

Thanks for the replies. It is making more sense, but again, how does one know what devices are safe for Lithium use?

 

[kitelights]

The battery chemistry dictates the voltage. The lithiums tend to run a little over (1.7V) while the rechargeables run a little under (1.25 V). Since alkalines are not intended for high drain use, they will drop their voltage rather quickly when used in high drain application. Rechargeables start off a little lower but will maintain their voltage through their cycle and then drop suddenly at the end. Lithiums will drop initially from their "over volltage" but will maintain a much flatter discharge than alkalines.

Most AA powered devices will run fine (usually better and longer) on lithiums. The reason that it's not OK in the SL is that the LEDs are already sharply overdriven with standard alkalines. The lithiums provide more voltage initially and maintain a higher voltage, since they don't drop rapidly like alkalines do.

There are several CPFers here that run their SL 4AA 7LED on lithiums, but I'm not one of them.

 

[jbrett14]

Thanks again for the reply. I appreciate the quick education.

 

[tater_salad]

I remember a cpf'er that runs his SL 7led on 3 lithiums and a dummy cell.

 

[jbrett14]

I too have read that. I would imagine this would cause the light to be a bit dimmer though.

 

[chumley]

I am one of those cpf'rs who use 3 lithiums in the SL 4AA 7 leds. I know that it is dimmer than 4 fresh alkalines, but the output is still good, and it doesn't dim as quickly as alkalines. I have been running mine quite a bit this winter, and it is brighter than alkalines would be at this point.

I will probably use alkalines in it during the warmer months ahead, and save the lithiums for colder temps.