Hi recently bought my wife a Cree headlight for her bike. It comes with a Li-ion battery x 4 pack. The batteries are shrink wrapped together in plastic with what looks like a fibrous cover plate at each end. A length of cable runs into one end of the pack. The other end of this cable has a plug and socket part which meets and connects to the headlight cable. Charging the battery with the included charger takes about 6-8 hours. Immediately after charging the batteries will run the light for at least ten hours. Trouble occurs when after charging, the batteries are not used for a day or two. Then the light will switch on for a couple of minutes before the batteries are completely flat. It's the same outcome whether the battery pack is connected to the light or not. Please can anyone tell me if this is likely to be a short circuit in the cabling, or due to defective batteries? Mike