Not sure this belongs in this section but I don't see a more appropriate place for it and may be helpful to those looking into battery mods. You do need a charger. This is a report on the UltraFire WF-139 battery charger. It's a 3.7v charger for 14500, 17500, 18500, 17670 and 18650 3.7v lithium batteries. It came from DealExtreme and cost $13.90 with free shipping. Time from order to delivery was 14 days. It utilizes 100-240 VAC or 12 VDC power source. The unit ships with a 12 VDC power cord but it does not come with an AC supply cord. It uses a common figure-8 style connector that you may have for other chargers or radios. If you don't have a cord you can make one up yourself or try to order it separately from DX. Just don't go to ratshack and try to buy one because it will cost you half again the price of the charger. This charger gets some bad reviews for overcharging with many people warning about standing guard over your charging process, charging in a fire-proof box, etc. Maybe I got lucky but the one I have cuts off at 4.12 to 4.16v depending upon the battery. It will send up to 5.38v to an empty battery bay and a higher initial rate to a battery drained to 3.6v. The spec sheet says it is a 450mAh charger. The two charging bays are independent. Charge time to a green light is very quick and leaving it on longer doesn't seem to charge any further. Additionally, leaving a battery in the unit for many hours after a green light also does not seem to add any additional charge to a battery. In all cases to date, the highest voltage I've read on a battery fresh off the charger has been 4.16v, no matter how long it was charging. I imagine there are many higher quality chargers available but the flexibility of this one (being able to charge batteries in the car on a road trip) makes it an okay unit for me.