2 x CR123A's vs. a single 18650 in my Streamlight Pro Tac HL questions.

[waxycap]

Hi,
I have a Streamlight ProTac HL (model #88040) and I use two rechargeable 3.0V CR123A's to power it.
(I use the light every day, and recharge the batteries every night).

I was playing with my friend's cheap little Ultrafire light, which uses a single rechargeable 3.7 volt 18650, and dropped that battery
into my flashlight for minute to see if it worked, and (as suspected), it did.


However.. was this a dumb idea?
Could I have fried my LED? Considering that the "appropriate" batteries for use in my light are two 3.0V's, and theirs is one 3.7V?

The reason I ask:
I would really like to use a single 18650 in my Streamlight (not sure which is the best), and eventually forget about using CR123A's altogether.


P.S.
Do mAh differences matter in regards to not damaging the LED?

thanks

 

[gearhead1972]

You won't damage the light, but you will see a loss in power probably, but an increased run time. 750 mah compared to say 3000 mah of an avg 18650

 

[waxycap]

You won't damage the light, but you will see a loss in power probably, but an increased run time. 750 mah compared to say 3000 mah of an avg 18650

I wonder why a loss in power?
I've been told that a loss in brightness would not occur because it is an LED designed to output a certain way.
Come to think of it, I've never seen this flashlight "dim" in any way. It is simply bright, or less bright (on the lower setting), OR it starts to flash on and off
as a warning of low battery and then it's just completely black after that.

What makes you say that a 3.7V battery would not hurt my 3V LED? Is there a scientific reason?

I would appreciate it if someone could keep answers separated, since I am a complete noob.
Sorry for not numbering my questions into distinct categories, but I thought I did a pretty good job at keeping the questions separated into things like volts, mAh, battery types. etc.

 

[gearhead1972]

I wonder why a loss in power?
I've been told that a loss in brightness would not occur because it is an LED designed to output a certain way.
Come to think of it, I've never seen this flashlight "dim" in any way. It is simply bright, or less bright (on the lower setting), OR it starts to flash on and off
as a warning of low battery and then it's just completely black after that.

What makes you say that a 3.7V battery would not hurt my 3V LED? Is there a scientific reason?

I would appreciate it if someone could keep answers separated, since I am a complete noob.
Sorry for not numbering my questions into distinct categories, but I thought I did a pretty good job at keeping the questions separated into things like volts, mAh, battery types. etc.

Ok so your light is regulated. This means the light will try to maintain the same brightness as the voltage drops, it will do this by increasing amps. It also may limit on the other end when the battery is full it may reduce amps.

Your light is designed to use 2 Cr123 batteries in series 3v 750 mah in series will give you 6 volts at 750 mah. Lets say an AW 18650 is 2900 mah and 3.7v, actually 4.2 hot off the charger, this will put less voltage to your light then it is designed for (though regulation may keep it at the same output.) This will give you over 3 times the run time, but the lower voltage will be pulling more amps out of the battery so it may be closer to 2 or 2.5 times the run time. You would have to put an amp meter on the the batteries to know for sure.

 

[ryukin2000]

I wonder why a loss in power?
I've been told that a loss in brightness would not occur because it is an LED designed to output a certain way.
Come to think of it, I've never seen this flashlight "dim" in any way. It is simply bright, or less bright (on the lower setting), OR it starts to flash on and off
as a warning of low battery and then it's just completely black after that.

What makes you say that a 3.7V battery would not hurt my 3V LED? Is there a scientific reason?

I would appreciate it if someone could keep answers separated, since I am a complete noob.
Sorry for not numbering my questions into distinct categories, but I thought I did a pretty good job at keeping the questions separated into things like volts, mAh, battery types. etc.

It didnt harm it because your light can handle up to 6v. 2xcr123 in series is 6v. Unless im wrong as I am also a noob.

 

[waxycap]

Ok so your light is regulated. This means the light will try to maintain the same brightness as the voltage drops, it will do this by increasing amps. It also may limit on the other end when the battery is full it may reduce amps.

Your light is designed to use 2 Cr123 batteries in series 3v 750 mah in series will give you 6 volts at 750 mah. Lets say an AW 18650 is 2900 mah and 3.7v, actually 4.2 hot off the charger, this will put less voltage to your light then it is designed for (though regulation may keep it at the same output.) This will give you over 3 times the run time, but the lower voltage will be pulling more amps out of the battery so it may be closer to 2 or 2.5 times the run time. You would have to put an amp meter on the the batteries to know for sure.

Thanks, man. That info might help me make some decisions.

I am learning all the time about batteries. It doesn't seem like there is much to learn about the flashlights themselves, other than what power they can or cannot handle (unless I plan to modify the flashlight)

I'll go from there.

 

[waxycap]

edit: *cannot delete this*

 

[waxycap]

It didnt harm it because your light can handle up to 6v. 2xcr123 in series is 6v. Unless im wrong as I am also a noob.

I suppose that's right.
I just read on another site today that if it's two 1/2 size batteries (CR123A's in this case) and not one, the combined voltage of the two smaller ones adds up to the maximum voltage allowed for that particular LED....
But now I am really confused and about to melt some $100 flashlights. LOL

 

[ChrisGarrett]

Panasonic USA sourced CR123As have ~1550mAh of capacity under a 500mA load, according to HKJ's test of a small sample size, or just about ~1200mAh under a 2A load.

http://lygte-info.dk/review/batteries2012/Panasonic Lithium Power CR123 UK.html

You put to of these in series and you're still at ~1200mAh, but you're now at 6.4v resting, probably 5.8v-ish under a load.

At two amps, you get about 2.3 Wh per cell, so 4.6Wh per pair, for ~$4 delivered.

A typical AW 3100mAh 18650 will give you about 9.6Wh, for about $20 per cell.

If you'll happy with the lower capacity running 2x3.0v LiFePo4s, that's fine, but I'd stick with the 18650s and I run ICR/IMR 16340s in single cell lights, so I'm a fan of that form factor, just not when I can run a larger, more efficient cell.

Chris