The problem that Sony had with their batteries was a manufacturing defect.There were metal particles suspended inside the battery shell making contact and short-circuiting.I have used lithium polymer batteries from ThunderPower.com with satisfactory results but I am switching to A123 batteries for more durability,faster charging times and less critical charging issues with balancing the dividual cells.As long as the A123 batteries are under-charged and under-discharged the batteries remain robust and have a very long life-cycle.Full size electric cars are using these A123 batteries without a charging balancer system and have zero problems.A very convenient battery pack is the Bosch 12volt screw driver drill.The pack is compact and fast charging.
