A good flashlight has two batteries ?

Hi guys,

Sorry if this question can sound silly but I was wondering what was the TRUE advantage of having a flashlight that would use more than one battery ?

- Runtime ?
- Power ?

Is a good one-battery flashlight better than a poor 2-batteries flashlight ? (I guess)...

Technically speaking, why and what would make a flashlight to have 2 batteries ?

Many thanks for your help !:thumbsup:

I prefer single battery lights..... Single 123/AA/16850..... Easier to deal with and manage recharging.... Also, when 2 batteries have different charge levels, that can cause issues...

For NiMH or other such batteries < vf of LED's, having more batteries in series means you won't have to boost as much.
Obviously you get more power.

hemdale said:

Technically speaking, why and what would make a flashlight to have 2 batteries ?

Click to expand...

I don't understand the question.

hellokitty[hk] said:

For NiMH or other such batteries < vf of LED's, having more batteries in series means you won't have to boost as much.
Obviously you get more power.

I don't understand the question.

Click to expand...

Yes sorry I meant: having 2 batteries (or more) is just for runtime reasons ?

If you have lower voltage batteries like NiMH or alkaline, then having two or more in series will help since the LED requires 3v+.

Not necessarily tru with incans. When ran in "series", you increase the voltage=more brightness (at least this is more true with Incans); when ran "parallel" you increase the capacity; Example; The Surefire M3 runs off 3ea. 3-Volt Batteries ran "serial" (in-line), giving you more voltage, but the same "capacity" as one cell. Where as the M6 runs two sets of three (6 Batteries) ran "parallel", still giving you 9-Volts, but increasing the capacity. That's why you can run an M3T bulb (MN15) off the M6 and get double the runtime (plus some). It's not necessarily 1+1 = 2, but that's the basics of it.

LED's mainly is to extend runtime, or increase the number of LED's you want to run (i.e. a Tri-Head), there by increasing your out-put.

A consideration specific to high power setups is the volt/amp relationship. To keep output power (watts) the same, when you have half the volts (one cell) you must have twice the amps. This puts more stress on thngs like cells and switches.

I don't see an advantage. I get great runtime and power out of my single-cell lights as well. It's more a function of the LED and driver in my opinion, not the battery. Example - my single AA Zebralight SC51 pumps out all kinds of lumens. More than many two-cell lights, in fact.

I'm by no means an expert but it would seem logical that all other things being equal two batteries (or more) would simply give you either more run time or a brighter light. Flashlight manufacturers make trade-offs in size and weight considerations in their designs as well which may dictate number of cells. Sometimes more cells would just be a requirement. If you're going to make a 1,000 lumen light you're not going to do it on one cell, at least not with any run time.

Keeping in mind that capacity is not the same at all current draws, it is usually possible to squeeze more than double the runtime out of a two-cell light than a similarly specced one-cell light. Keeping in mind the equation of W = A * V, if you are drawing 3W off a 3.0V cell, then you are pulling 1A, but if you are drawing the same 3W off two 3.0V cells in series for 6.0V then you are only pulling 0.5A, which puts less strain on the cells and in an efficient circuit, can run for more than simply swapping in a second cell. It is also important to note that buck circuits (used when the battery input voltage is higher than the LED needs) are noticeably more efficient than boost circuits (used when battery input voltage is lower than the LED needs).