P7 using A123's at 3.3V

[James35]

I like my A123 batteries. They put out 3.3V. What kind of lumens can I expect with a P7 C-bin? Is it going to be noticiably dimmer than if I were to run it at 3.7V?

Will a D2DIM driver board reduce the output even more (vs. direct driven)?

 

[IMSabbel]

At 3.3V, you can expect something in the lines of 1A. At 3.7, you would get >3A (but most likely ,your battery voltage would sag).

So yeah, its a LOT dimmer. With my lap PSU, its even really noticeable going from 3A to 4A (so little drooping). Going form 1 to 3A is the difference between a P4 and a P7...

 

[James35]

Oh no. That bites! I didn't think it would be that much of a drop. Crud! So 3.3V isn't really taking advantage of a P7's capability? I can go to 6.6V, but I think that would be way too much. Hmmmm...

 

[IMSabbel]

Oh no. That bites! I didn't think it would be that much of a drop. Crud! So 3.3V isn't really taking advantage of a P7's capability? I can go to 6.6V, but I think that would be way too much. Hmmmm...

That would kill it. Seriously.

The P7 can be driven quite well by a "normal" 18650 cell.

The A123s voltage is just too low for that.
You also have to consider that you wont get that 3.3V at the led: every contact eats a few mV...