Welcome to the forum.

There are higher capacity rechargeable batteries available, but you need to buy the correct charger. The problem is that I am not sure that the more expensive batteries will give you much more than a 25% improvement in running time.

In any case, here is one review --> https://www.digitaltrends.com/buying-guides/best-rechargeable-batteries/

The problem with using other types of batteries is going to be fit.. The Tamiya 7.2V battery used for RC cars might work, but where will it fit? It also needs a special charger with the correct plug.

The lithium-ion batteries are too dangerous for children under 8 years of age and they need a special (expensive) charger.. They need to be discharged to a storage level when not in use for an extended period.

Your high battery consumption means that your son is really enjoying the trains, and this is a really good thing.

Hi,

xxup, thanks for the tips on the batteries. I have been using Varta rechargeable batteries but they seem to lose their capacity in storage in 2 months or so.

On Li-Ion I was not meaning raw batteries but rather something like camera batteries that have a seperate charger, or even a complete power element - to replace the entire AA housing unit - that would have a i.e. USB or round (like in laptops) charging port or similar. Not a bad product idea actually.... .

But that does not exist so I will get some new AA batteries.

Mike while I agree, with a dysfatic son a powered track will have to wait for 2-3 years.