Here is a link to a site for making a very powerful halogen light! Hope you enjoy it! D Works great!!! http://www.instructables.com/id/BIKE-LIGHT-500-Lumen-"Mt.Bike"-for-under-10-bucks-/
That's a Li-ion pack not NiMh. Even though it doesn't mention it in the description in has to have a low voltage cut off, if you run a Li-ion battery "dead" you've destroyed it.
Better solution would be to buy a Li-ion pack meant for electric R/C (11.1v 1200 mAh packs can be found for less then $20), a cheap lipo brushed motor speed controller (30A can be found for under $6 shipped on ebay) driven by a manual servo adjuster (under $10), toss in a charger (about $30, smart chargers aren't cheap but will charge fully in about 20 minutes) and you'd have a heck of a setup.
That is not a cost effective solution unless you absolutley need adjustable light which is a bad idea anyway. The helmet cam and LED packs from that link certainly have LVC built-in otherwise they would be "one-use" batteries. If weight is at a premium then lithiums with a cheap protection circuit like those from All-Battery are better but still pricey compared to nickel chemistry.
All-in-all NiMh AAs are the most cost effective and simplest solution. This is my opinions having dealt with PB and lithium alternatives on many occasions.
The new 1.6v NiZn AAs have radical advantages over all the above but are still in the expensive mode. I just bought $200 worth last week because they don't suffer from low voltage issues plagueing current Ni cells and that solves problems in several of my applications.
In radio shack i saw a 8.5 v battery with charger... Wouldn't it be better to buy two of them and somehow to make it yo 12V ?That's a Li-ion pack not NiMh. Even though it doesn't mention it in the description in has to have a low voltage cut off, if you run a Li-ion battery "dead" you've destroyed it.
Better solution would be to buy a Li-ion pack meant for electric R/C (11.1v 1200 mAh packs can be found for less then $20), a cheap lipo brushed motor speed controller (30A can be found for under $6 shipped on ebay) driven by a manual servo adjuster (under $10), toss in a charger (about $30, smart chargers aren't cheap but will charge fully in about 20 minutes) and you'd have a heck of a setup.
As mentioned in several other posts LED with rechargeable AAs is actually the best solution. Most HT magnetos do not fare well with the extra load. The add on magneto coil has potential (pun).Why not use high output / low voltage / led's.
I mean led lights.
Then run the white 6V line off the HT magneto to them.
I have a bicycle light that is led and pretty bright.
Takes 4 aa bateries.
4 X 1.5v = 6Volts.
See what i'm talkin about.
I have even seen a higher power magento for running lights on the net.
I'm gonna try anyway.