3xAAA vs 18650 in a SolarForce L2i

I still cant really understand why 3xAAA (eneloops equals about 2300mAh and 3.5+Volt) and a 18650 (with 2200mAh 3.7V) would make a big difference in runtime, and output?

Please explain!

I was just reading another thread saying that a 14500 battery with 900mAh outperformed an Eneloop 1900mAh in output and runtime.

I have a Solarforce L2i with a low voltage XPG R5 drop in, using 3aaa eneloops to power it. (first didnt want to have liion batteries, now Im thinking about getting some)

1.Why would a 18650 battery last longer? because they have about the same Voltage and mAh.

2.Also would the Xtar 18700 battery fit my L2i? (seems that people like these a lot here on BLF)

3.Somewhere in my house I have a 14500 battery (received with my sipik clone, but have lost it somewhere)
If I use a spacer, how would that compare against 3xAAA?


3xAAA in series is ~800mAh@3.6v.

L2i has problems with 18650, a bit too short (but manageable with tightening hard), so I guess with 18700 there will be more problems.

ok.. I was thinking 3xAAA would be 3x800=2400 ?

Assume X identical cells:

In parallel - voltage of one cell, capacity is X times one cell.

In series - voltage is X times one cell, capacity of one cell.

If they don't have identical charges/voltages the math is different but the idea is the same.

Im getting there!!

but I guess Im more of a visual person.. so if someone had a simple drawing that would really help with explaining parallels and series, including the numbers..

Almost getting there

You can read more about it here: http://batteryuniversity.com/learn/article/serial_and_parallel_battery_configurations

And the battery university is a great resource for learning about batteries (and even though its online version is free of charge, I considered buying the printed book... if only it wouldn't cost like a good budget light just for shipping...).

Parallel = the cells point the same way , and all make contact .. So + face one way , and neg face the other way and all the cells are configured the same .

This way the voltage remains 1.25 [?] but Amps go up as it becomes 3x800mAh = 2400mAh

If in series , + to - , then voltage goes up , but amperage stays the same .

As for the L2i , there are some simple mods to make it 3xAAA and 18650 capable ...

Thanks Haggai for the link.. that really made it much clearer. and I think I start to get it.

Also old4570 thanks for the explanation.

So if I understand that correctly, the 3xAAA "cartridge" that goes in the L2i is in series!
So, if I would have them Parallel, I would have a much longer runtime, 3x800mAh, but less brightness!
So in low mode, the light would have a 3x longer runtime..

1.Then my next question, if I would have 3xAA batteries also 800mAh each, the light would still have the same runtime? (I know that wouldnt fit in the body, but just to make it clearer)
2.But if I would have a flashlight with 4xAAA 800mAh batteries, the flashlight still would have the same runtime...
because the mAh doesnt change?
I think at this point some calculation need to be done! (I think that time the Voltage needs to be multiplied by the mAh to get the total ....""thing"")
3.When I would have them in parallel, and I multiply the mAh per cell times Voltage....it would still be the same Total though..!? so that means at the same current, the light would still have the same runtime..

now starting to confuse again..

please help again

Lets see if I got the point.

Say there is a 1D maglite with a low Voltage Led that only requires 1.2V+..

If I put a 2xAA to D spacer in there, both AA in Parallel the light would have a doubled runtime
than to put them in Series?

Or would it be the same, as we have to calculate the mAh with the Voltage?

An LED need ~3.4-3.7V to work. You can however have a booster circuit to boost 1.2V to 3.7V.

Runtime depends on total watt. Watt is Voltage * Amperage.

If you have 3 batteries. A D-cell, and two AA cells - all with the same mAh rating(say 1000mAh), and 1.5V.

If you plug the two AA cells in a D-cell converter(in parallel), the voltage would still be 1.5V, but the mAh rating would be 2000mAh. If you had a 3 AA to D-cell converter it would be 3000mAh.

If you on the other hand had a long flashlight where you could plug the 3 AA batteries in series, you would have 4.5V and 1000mAh.

mAh rating means how many mA the light can draw at it's voltage, for an hour.

If you have a 1000mAh batteri, that uses 2A at the voltage the batteri has, it would be depleted in half an hour.

The L2I batteryholder wires all 3 AAA batteries in series, so you would get 4.5V(with alkelines), and ~800mAh.

If you look at figure A and B in this picture, you can see the difference between series and parallel(only with resistors instead of batteries).

Voltage x Amps = Watts

Lets call the batteries 1.5v to simplify things

In paralleled Voltage remains the same , but the more cells you add , capacity increases ..

Lets call the AAA 800mAh = 1 x 800 = 800 / 2 x 800 = 1600 and so forth - in parallel - forget about voltage as it does not change !

Now lets try series ..

In series , where the cells are connected to each other + to - in a series , Voltage goes up and capacity remains constant

1 x 1.5 = 1.5 / 2 x 1.5 = 3 / 3 x 1.5 = 4.5 and so forth , only the voltage changes - forget about capacity - its now a constant ..

Now - How this affects you in a flashlight - is very variable .[ Series ]

It depends on the driver - emitter and battery combination ...


A very simple way of understanding is by using Watts

If the light is regulated to a constant 5Watts [ for arguments sake ]

a single 1.5v battery would need to ? 5 divided by 1.5 = 3.3333333 Amps

Two batteries would need to ? 5 divided by 3 = 1.666666 Amps

Three batteries would need to ? 5 divided by 4.5 = 1.1111111 Amps

Four batteries would need to ? 5 divided by 6 = 0.83333 Amps

Now we are talking series here so as the voltage goes up , current should come down = more run time , even though battery capacity has not changed .

Now this is by no means exact , but hopefully explains the basics of how voltage affects things .

Hi Old4570, the last part of your post explained it the best for me..
I guess with including the Wattage, it makes more sense, because the batteries would have to use less "juice" to come up to the used Wattage.

That makes sense... Withou using "Watt" I couldnt get the picture... You made my day ;)

I did a simple mor to L2i clicky with this http://www.shiningbeam.com/servlet/the-93/Forward-Tactical-Click-Switch/Detail

There´s old4570´s instruction somwhere here or CPF.

Basically it goes like this: Unscrew old clicky out with tweezers. Take all out, black boot also. Turn rubberboot inside out, cut the small nub away. Assemble with new clicky = 18650 fit easily.

For AAAx3 holder use, the holder must be trimmed a bit slimmer to fit inside tailcap to make contact with new clicky.

I originally gifted it to my dad but recently took it back because you can't find these anymore, haha. I'm replacing it with someithing else, but he still has a DRY and X9 in the meantime so I think he'll survive just fine :)

I'm sorry, but in my book you can't beat a compact P60 that can still do this on AAA:

Mouse-over for L2i UF XM-L on 18650; Mouse-out for 3xAAA