Burntime calculation help

[Deal87]

[FONT=&quot]What would the runtime be with on max power with the following setup:[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]3x SST 50s individually controlled by 3 hipcc drivers (1 per LED)[/FONT]
[FONT=&quot]1x D2 flex to allow variable power outputs[/FONT]
[FONT=&quot]5x 18650 cells 2600mAh @ 3.7V in series x 2 in parallel (10 cells in total)?[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]I understand the cells alone would give me the following calculations:[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]18.5v and 5.2Ah= 96.2Wh[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]Could anyone confirm the runtime as I am confused about how much power the drivers will need to run. From the data sheet I can see they require 0.5V to run how would this tie in with the rest of the calculations I need? Thanks in advance [/FONT]

 

[ti-force]

You need to know how much current (amps or mA) all of the drivers will pull from the batteries. Once you know that, take 2600 x 2 = 5200mAh. Then divide 5200 by the current draw and you will have a rough estimate.

 

[Noctis]

Geez, how many lumens do you get with that setup?
And is that even possible in a flashlight?

I've been thinking that Triple SSTs would be the next most powerful setup in a relatively small package, at least until Cree has their new LEDs available in mass production.

 

[gcbryan]

We need to know how hard you are going to run the emitters. Are you pushing each emitter to 5A?

 

[Deal87]

hi, so if I run the LED's at there most efficient current draw of 1.75A would I be right in saying the following for a rough calculation:

2.6Ah x 2= 5.2Ah

5.2/(1.75x3)= 0.99hours?

As far as I can tell the hipcc drivers draw 1.1A so with 3 of these running would the calculation change to:

5.2/(1.75x3)+(1.1x3)=0.608hours?

Or have I got the wrong end of the stick?

Thanks guys

 

[ti-force]

hi, so if I run the LED's at there most efficient current draw of 1.75A would I be right in saying the following for a rough calculation:

2.6Ah x 2= 5.2Ah

5.2/(1.75x3)= 0.99hours?

As far as I can tell the hipcc drivers draw 1.1A so with 3 of these running would the calculation change to:

5.2/(1.75x3)+(1.1x3)=0.608hours?

Or have I got the wrong end of the stick?

Thanks guys

I'm not really familiar with these drivers, but I would think if current measured at the emitter is 1.75A and the driver has 80% efficiency, then a tailcap measurement should be roughly 2.187A.

So 2.187 x 3 = 6.561A and

5.2/6.561 = .79, so roughly 47 minutes of runtime if I'm correct. If I'm not correct, maybe someone will step in and clear things up.

 

[gcbryan]

I'm unclear as to exactly how many batteries you are using. The figures need to be converted from Watts to Watt Hours. You guys are just referring to Amps.

One SST-50 needs 3.7V when driven at 1.75A...is that correct (I haven't checked the data sheet) however you have said that you are going to run it at 1.75A.

So 3.7V * 1.75A = 6.4Watt and you have 3 leds so 3* 6.4 W means you require 19.4 W for this flashlight.

Each battery will provide in Watt Hours 3.7V * 2.6aH so 9.62 WH. As you can see 2 batteries will essentially power this light for an hour (9.62 WH *2 =19.24 WH).