You can get Li batts that work on a BCG. They are 3.7v so equivalent to a tricell car. They also only weigh 4g which is heaps less than NiMH batts. At 145mAh it is slightly less capacity than NiMH batts but you get the higher voltage. You just need to have a Li charger to charger the batt. Plus if you are on a budget the Li cell tend to cost a bit!