Ledengin and 7.4V 14500 battery pack milliamperage question

[SonicSculpture]

I have 2 UltraSaber aeon V2's with white P4's that I first upgraded by installing 1200 mA Constant Current Led drivers. I just replaced the P4's with 10W Ledengin cool whites, using two dies from each respective LED, and switched out the 4 AAA battery holder for a 7.4V 14500 Li-ion battery pack. I began by re-using the drivers, since they were already wired up, but soon discovered that I could get more light by going right from the battery pack to the pair of dies, which I had wired in series in each saber. Consequently, I retired the drivers for some possibly future use. But I do not know how to do the math. Can anyone tell me how many milliamps are going to each die in the pair I'm using by driving them directly from the 7.4V battery pack? If it's no more than 800 mA each, would it be safe to add another 3.7V cell to the circuit? Please advise! Thank you!

[Silver Serpent]

You'll need a multimeter to read the current draw that is going to your pair of LED dice. Based off the LEDEngin spec sheets, each pair of cool white dice in series will need about 7.3v, and your battery pack is 7.4 (a little higher when fully charged).

I wouldn't add another cell to the circuit, unless you wanted to add your LED drivers back in.

[SonicSculpture]

Thanks for the info! I thought a third power cell would be risky. If I stay with the pair of 2.5W dies and the 7.4 V battery pack, would it be enough power for a 2A Constant Current LED Driver (for 1A per die) or would I then need to add another power cell? Thanks again!

[Silver Serpent]

If you're using a 2A driver and you want to deliver 1A to each die, then you'll need to wire them in parallel instead of series.

If you want to leave them in series, then you can run it fine using a 1000mA buckpuck or something similar.

Adding a third cell to your power pack will increase the voltage to 11.1v. If you do that, you will need something (LED driver, buckpuck, resistor, etc.) to bring the voltage down to an appropriate level for your LED. You have enough power to run your LED in most any configuration. There's really no need to use a 3-cell pack. If the runtime is not to your liking, an appropriate upgrade would be to use a 2-cell 18650 battery pack (if it fits) or else have easily swappable battery packs, and just carry a spare.