3C P7 Build Questions

[Anto]

I'm planning to build a P7 Mag with the following host:

3C Mag
(3) 5000mA LSD C NiMH ~ 3.6v

D***I P7
(2) 4x 7135 Sandwich

I've been sifting through the P7 threads but I can't find answers to a few questions.

1. Would this battery setup be enough to drive the sandwich @ 2.8A?
2. Roughly how long will the runtime be, and what will the graph look like (output vs. voltage sag)?
3. Since the input voltage and output voltage are close to each other, will the board need to be thermally potted?

I know that 3xD or 4xC cells are an optimal setup, but I like the form factor of 3C - how does it compare?

 

[jar3ds]

I'm planning to build a P7 Mag with the following host:

3C Mag
(3) 5000mA LSD C NiMH ~ 3.6v

D***I P7
(2) 4x 7135 Sandwich

I've been sifting through the P7 threads but I can't find answers to a few questions.

1. Would this battery setup be enough to drive the sandwich @ 2.8A?

considering that the P7 could have a Vf > your Vin @ 2.8A, its already over what you have as your Vin

2. Roughly how long will the runtime be, and what will the graph look like (output vs. voltage sag)?

you'd be direct drive almost right away...

3. Since the input voltage and output voltage are close to each other, will the board need to be thermally potted?

I wouldn't even bother with the 4x7135 since Vin is so close to Vout

I know that 3xD or 4xC cells are an optimal setup, but I like the form factor of 3C - how does it compare?

:wave:

 

[LEDninja]

I got an Elektrolumens built 3C P7 direct drive.

2.8A achieved with freshly charged NiMH batteries. 2900 mAH Ray-O-Vac, 4500 mAH LSD Accupower.

In actual use brightness does not seem to dim much to the eyes until batteries are exhausted, then dims very rapidly. Like from bright to no light in 1 minute.

~1 hour with the ROV bat. I was alternating lights, do not have an exact time. Expect ~1.5 hours with the 4500 mAH ones.

Gets warm but not hot.
My 18650 EDC-P7 got HOT fast.

 

[Anto]

Wow, I thought the numbers would be higher. I'm guessing voltage sag really brings the runtime down?

Looks like I'm going to be running 4xC cells in a 3D host.

 

[Mark620]

Wow, I thought the numbers would be higher. I'm guessing voltage sag really brings the runtime down?

That would be amp draw.

 

[Anto]

Got it..
last question,

Runtime vs brightness with 4xC compared to 3xD?

 

[Mark620]

Got it..
last question,

Runtime vs brightness with 4xC compared to 3xD?

Well 4C is too much voltage. 3C with 4500 mah capacity .VS. 3D with 10000mah capacity I would say the 3D would last over 2X as long.