Best battery for this popular combo??

[Toddman214]

Hello all. This my first post, so go easy on me.

I am building my first laser, using a popular combination of a rkcstr v3 micro drive and lpc-815 red diode. I plan to run the LD at 400ma with plenty of heat sinking. What I'd like to know is what is the most compact, longest lasting, rechargable battery setup I can get without generating too much excess heat. My original design had me looking to use 6 AA energizer rechargeable batteries (7.2v total) but, that's quite heavy and bulky. I've been looking also at these rechargeable cr123 batteries which come in 3.7v each. I'd only need two of these to match the output of 6 AA's, at 7.4v total.

There almost has to be some sort of trade off here, but I dont know what. Would the cr123's be a better option, or might there be an even better option than either of these? Sorry for the noob question, and thanks!

Todd

 

[LarryDFW]

Toddman;

The #18650 is the most advanced battery available for hobbyists.

It does not have any self-discharge problems, that the AA will have.

It will run your Red for a long time.

Since your Red needs ~3VDC, the best solution is a LM1117 driver for low voltage drop.

(You don't need 7.4 VDC to end up with 3 VDC)

JIB makes a nice one that can work with a simple resistor change:

http://laserpointerforums.com/f39/fs-lm1117-based-linear-driver-1-3a-fixed-60213.html

LarryDFW

 

[Toddman214]

Thanks Larry. I do want to use the driver I currency have. I looked into the 18650 batteries and I think I like them. But, these are lithium ion. Can they be drained all the way down? Another hobby I have is r/c cars and we use very powerful lithium polymer packs that have to use a low voltage cut-off, or else they can "puff" or explode. Do these 18650 cells require some sort of low voltage cut-off?

 

[anselm]

You can get 18650s with incorporated protection circuit.
They are supposed to prevent overcharge (useless when you have a proper charger) and overdischarge.

 

[LarryDFW]

Toddman214;

I have used hundreds of these "name brand" #18650 cells without protection circuits.

I have never caused a problem from low discharge voltage.

I have used them in RC trucks also.

LarryDFW

 

[ravenit]

You could use these if you want the 123 battery $5.21 - TrustFire Protected 3.6V 880mAh 16340/CR123A Batteries (2-Pack) - Batteries
Rechargeable lions.
Cheap and then get a charger all set to go.
2x battery's for 7.2v as long as they fit in your host oh and welcome to the forums. Im new myself but learning fast.

 

[Wolfman29]

You really, *really* don't need that much voltage. I am running an LOC at 382mA with a single, 3.7V li-ion battery and it is working just fine. I am even using a DIY driver, which generally has a higher dropout than the Rkcstr.

 

[Toddman214]

I already have the rkcstr driver and do want to use that. But, it does require a minimum input voltage of 5.5v for a red diode. I'll be driving it at about 400ma. I may still be over voltage at 7.2 thought.

 

[Cyparagon]

Rechargeable lions.

I lol'd

 

[ravenit]

Ok from the specks of that driver -Input voltages of at least 3V up to 15V, where your input must be at least 2.25V + Vf of your diode (ex. a 3V red diode would need 5.25-12V+ for regulated operation)
Excess volts just turn into heat on the rkcstr you will be fine

 

[LarryDFW]

I have operated several LOC red diodes . . .

off of a 18650 cell and a LM1117 driver (or LM317).

It will operate @ 4 VDC battery voltage.

LarryDFW