Power Question

[scottymcneill8657]

I need help with power for a led flashlight- I currently use a 12v 7ah sealed lead acid battery and need something lighter. I'm running a 32v 100w led through a constant current driver(handles up to 5A) to a 150w DC-DC boost converter(10-32V input to 12-35V 6A output) plus a heatsink. LED draws 3A to run- I want to run this for an hour at least and be cheap-ideas?

 

[Norm]

Moved to Batteries Included - Norm

 

[StorminMatt]

There are multiple ways to go about this, depending on which battery chemistry you want to use and whether you need a stable 12V input. But what exactly do you mean by 'cheap'?

 

[Curious_character]

To get lighter, you have about three choices:

NiMH - You'd need quite a few cells, and a charger for them. Lighter than the lead-acid, and probably the least expensive option.
LiFePO4 - This will be around half the weight of the lead-acid. The nice thing is that you can use the same charger you're now using for your lead-acid. A 7Ah LiFePO4 battery will provide considerably more energy than the 7Ah lead-acid at the 1C discharge rate. The only problem is that they ain't cheap -- a 7Ah 12V Tenergy battery goes for around $140.
Li-poly - Widely used by RC hobbyists, these are relatively economical (although still considerably more than lead-acid), small, and very light weight. A 3 or 4 cell battery should suit your purpose, and again, you'll get a lot more energy per Ah out of it than the lead acid at the 1C discharge rate. A downside is that you'll need to buy a charger, which will probably be around $20. I've been pleased with the few batteries and chargers I've bought from Hobby King, but RC enthusiasts can surely give you more and better recommendations. Hobby King's prices are probably representative for decent quality batteries. I'd steer clear of ones that are a lot cheaper.

I think that's about the extent of your choices. All are unfortunately more expensive than lead-acid which is just about impossible to beat for price.

c_c