2x C-size batteries for 4-6V?

[marschw]

I'd like to power this driver with 2 C-size cells. It works with Alkalines, but the result isn't very bright (I'm running an SSC P4 on it). I suspect the problem is that the 3.0V total I get from the alkalines is too low.

The driver can supposedly handle up to about 6.0V (maybe a little less). Does anybody know of something that would fit well in a light meant for 2 C-size cells, and provide about 4-6 volts?

The closest I've found is 4x 1/2C cells, but I've only seen them in NiCad. Maybe 2x C-size lithium polymer cells? I haven't been able to find those, though, and I'm not sure how far above 3.0V they get when full.

 

[kavvika]

That is a linear regulator, which means it acts as a variable resistor to lower the voltage, and cannot raise it. It works well with one Li-Ion cell or 3-4 NiMh cells (it can get hot on 4). You cannot go above 6v. 3x 4/5Sub-C's from cheapbatterypacks.com are the same length as 2 C's, but only have 2200mAh capacity. They're a bit narrower, so you might need to roll them in a sheet of paper or find some tubing at a hardware store. Those might be your best option.

 

[TorchBoy]

At a push I suppose you could use a power diode to drop the supply voltage (0.6V per diode) so the linear reg doesn't have to do quite so much work. A bit wasteful though.

 

[marschw]

At a push I suppose you could use a power diode to drop the supply voltage (0.6V per diode) so the linear reg doesn't have to do quite so much work. A bit wasteful though.

What's a power diode? If it's just a diode that's capable of high amperage, shouldn't that not drop the voltage at all?

Unless I put it in backwards, I suppose

 

[TorchBoy]

What's a power diode? If it's just a diode that's capable of high amperage, shouldn't that not drop the voltage at all?

A power diode is a diode designed to handle lots of power. Any diode will have some voltage dropped across it - it takes some voltage to get it to switch on, as you'll probably be aware of if you've used a few light emitting diodes yourself. White light emitting diodes have a higher voltage drop across them than the non-light emitting diodes I'm thinking of to get rid of a bit of extra voltage.

 

[VegasF6]

I wouldn't even run that board at 6.0V without a heatsink for the amc7135 IC's. I have run it on 3D alkalines and 3D nimh's with very good results. In fact, I have done it about 8 times now.

So, for a 2C build like you are wanting, you will either need to find 3 nimh that fit, (take a look at 3 4/5 sub C's, they should fit easily) (edit: I see that KAVIKA made the same suggestion) or perhaps a C size Li-on and a spacer.

Of course, this is all just my opinion.