I apologize if this has already been addressed but I have literally clicked on all 113 pages and cannot seem to find the answer I am looking for.

My 6 year old son found my old car at Grandma and Grandpa's house and we have been running it for the last week or so but I would like to get a little more run time for him as economically as possible.

Currently it has a Futaba FP-R112JE receiver with a Novak Rooster ESC and NiCD batteries that were bought in 1998.

My question is it possible to run NiMH batteries without changing anything? If I need to upgrade electronics what is required.

Thank you in advance for the help.

Running it with NiMH batts isn't a problem. The main issue is charging them, while very similar to NiCad for charging, ideally a lower delta peak value should be used as NiMH are less tolerant of heat and overcharging. What charger do you have?

The only thing youd need to change is the charger.

I'm not a big fan of either power source, but, changing to the new Lipo power source, would require a little more outlay, $$$ wise. Charger, batteries, of course and at least an ESC that is compatible with Lipo.
Don't be scared off with stability tales of Lipo.
If your going to jump in, save yourself the in between and go for it. JMHO.

I have a dynamite mega peak charger

I appreciate the opinion but I am not looking to spend that kind of money just yet. Next week it could be something completely different.