View Full Version : resistor question

09-11-2016, 07:56 AM
Hi all, let me start by stating i'm a first time saber builder.

I have purchased most everything i need and am in the process of final design.

My question is about the resistor requirements for foc using onboard Pex.

I have a pack of 7.4v Li-ion 1050mAh 14650 batteries

a cf8

a blue/royal blue/ white tri-cree (white for foc @ Forward Voltage @1000mA = 3.15v)

I'm not sure that my understanding of the manual is correct. From page 39/40 i believe i need a 4.7ohm, 4.7w resistor for foc.

Does this sound correct? What will my battery life be expected to be?

Any and all info is appreciated!

Silver Serpent
09-11-2016, 12:36 PM
Resistor is correct. You're looking at about half an hour or so of runtime. You could bump up to a larger pack made with 18650 cells and get more runtime if you need, or else design your saber to allow easy swapping of battery packs.

09-11-2016, 01:16 PM
hmm...... what is my best option for extending that run time? two 18650 wont fit......
should i hack the board to run on 3v?

Silver Serpent
09-12-2016, 06:45 AM
That is another option. You could do the single-cell hack and use a single 18650 cell. Or a pair of 14650 cells wired in parallel. There are several options.

09-12-2016, 12:46 PM
I have a pack of 14650 in series, i suppose i could change those over to parallel and double my ma to 2300ma @ 3.7v

Assuming my new voltage supply of 3.7v i would need a 1ohm 2w resistor for foc. does this sound like a better setup?

Silver Serpent
09-13-2016, 06:38 AM
It would have a longer runtime with that setup.

If you want maximum runtime with minimum space, http://www.thecustomsabershop.com/Panasonic-Li-Ion-18650-37V-3400mAh-PCB-Protected-Rechargeable-Battery-P853.aspx is the way to go. I don't know what your saber design is like, so picking out battery solutions is a bit tricky.

There are many, many options when building a saber. You typically have to make some compromises at some point. You can go for the brightest, or the loudest, or the longest running, but you're not gonna get the best of everything without building an ENORMOUS saber. :)

09-13-2016, 03:08 PM
Thats what i figured. Thanks for the replies, its been VERY helpful! :D