Xtar H1 Headlamp-14500 Battery explanations needed?? Voltage? mAH rating? Recharger?

I've decided to get the Xtar H1 headlamp set up, after much research on the forums here. I'm not familiar with the 14500 rechargeable Lithium battery at atll, other than seeing that it will push the Xtar H1 to anther level.

I see that I can get the 14500 in several make ups.

mAH ratings-do I need to concern myself with this? I kinda understand that as the number goes up, the battery will last longer?

Voltage rating-the Xtar H1 will except .9-4.2v, so is there a best voltage for this OR any light. I know that I'll be using it in the cold weather to hunt. I think I read that lower voltage batteries work better in cold? Peak & average voltages are mentioned on these battery descriptions also...I'm really clueless about this voltage thing, can you tell?

Brand-is there a best brand?

I've got a couple of rechargers, will they be fine for these 14500? Powerex recharger for AA AAA, not to much in the way of description on the bottom, INPUT dc 18v 1000ma. My other recharger, a LA Crosse Technology charger, has "Accus 300-3000mAH & DC 3V" on it. DO I need another recharger as well? I'm assuming yes? If so, is there a recommended recharger for the 14500?

Protected OR unprotected cells?! I'm assuming getting protected will just make it easier, as I'm also not sure about this issue

Any help would be nifty and appreciated...thanks, Kevin

14500 refers to the size of the cell - 14 mm diameter, 50 mm length. Basically the size of an AA.
mAh refers to the capacity. The higher the number, the more capacity. A typical protected 14500 li-ion cell is about 750 mAh.
Li-ions come off chargers designed for Li-ion at just below 4.2. As the voltage drops, the capacity is being used. (A common charger for a 14500 Li-ion cell should deliver about 500 ma.)
Li-ions should never be over charged (i.e. above 4.2 V) and never over discharged (3 - 3.5 is a good basic range for safe minimum discharge). Protected cells have a circuit to cut off below 3 V and usually a heat cut off, too. A voltmeter is a good tool so you understand the state of your cell and they are not expensive (see cottonpickers). Also, it is not a problem and may even be good for the long life of the cell to top off the cell. So if you read the voltage and it is 3.9, it is OK to top off the cell back to 4.2 V.
When used properly, Li-ions are safe. But there are a lot of bad stories and you can use the search function to find them. There is also a lot of good and important information on this forum and at Battery University. You should read up before making the plunge. Also, HKJ does very good reviews of cells and chargers. Other people do, too, and you can search for the reviews.
"An educated consumer is our best customer." Sy Syms