18 July 2019

Battery Life.

Marv is hard for the ws2815 over the ws2813.

The problem is that it needs it 12v nominal.

That needs three 3.7v Li-Ion cells in series.

That's a real issue inside the tube I've selected.

I can stuff:

6x 14500 for 1,680 mAh at 11.1v


3x 16650 for 2,500 mAh at 11.1v


Go with the ws2813 and:

2x 18650 for 3,400 mAh at 7.4v.

The 2815 is supposed to be more efficient, but I admit defeat in figuring out the terminology.

My 35" blade will be running 258 LEDs.

Who here can figure out the ballpark for batt life?


  1. What you can't put a boost circuit into it.

    1. I cannot. That's Marv's side of this project with his tasty chess club brain and electrical engineering degree.

  2. Also where are you finding 14500 with an actual capacity above 900mAh?

    1. Panasonic 14500's are said to have a reliable 840mAh. Six of them, two packs of three, should add up to 1,680 mAh at 11.1v.

      I've got several that run my little Cree flashlight which might have 600 mAh, and have 2,000 mAh printed on the side.

      The Panasonic brand batts are also expensive. $4 each or so.

  3. Angus, if you are using common LED's (not high power) then you can assume around 15milliamps per led in power consumption. Then 258 LED will consume 3.78 Amperes per hour. This is back of the envelope as I am going by old data, have no clue if modern low power LED consume less power that they used to when I was designing stuff back in the 80's. So I will guess you get about 1 hour continuous use worse case and maybe 1.5 hours best case.

    1. They're RGB LED. Marv says if all three are running at full bright (white) then they pull 20mA each.

      5,160mA draw! 19 minutes at full blast with the six 14500's running at advertised capacity.

      He also mentioned some Russian saber builder who keeps quoting 40% of that draw for other colors and being dimmer, 2,064mA at 40%. Almost 49 minutes of play time with the six 14500's!

      Even if I am stuck with the 500mAh ones, should still be half an hour of goofing off in them.

  4. Correction 3.87 Amps, I am dyslexic until coffee kicks in.


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