martin wrote:Question: will that just supply 4.5V until the Lipo's are dead?.... A buck with a lipo battery level LED status would be nice.
Yes, but you tend to just use lipos differently (or I do at least), they don't mind being constantly topped up and don't like to be stored full/empty so you get used to just using them to the halfway point, the packs are relatively cheap so if I'm flying my quad copter I just go outside with 3 in my pocket and one in the quad normally that's plenty of flying time but if you're really keen you just come back in and rotate them through the charger. With Real FX I'd suggest just one on the charger one in the car should do and you just change after 'x' number of laps, the less you have taken out of a pack the quicker it tops up anyway.
With different current draws you soon work out how many packs you need ie higher current draw set ups need more packs in rotating to allow for the charging cycle.
This all may be a bit of a waste as I trust that the stock set up works, it's just hard to get my head around as in RC cars/planes alkaline was replaced 15? years ago by NiCD and improved soon after with NiMH, and these days no one even bothers with anything but LiPo.