Don't panic about the above thread. It sounds like you are using stick packs, so a balance board will be useless.
The budget packs are ok to be run fairly empty but I would stop running as soon as you notice a drop in speed or acceleration and then set the pack away to cool. Maybe investing in a fast charger would be good so that you wouldn't have to wait 4-6 hours between runs.
You might want to consider investing in a set of ball bearings too, which will reduce wear to the car and give you longer runtimes as well. Check that everything runs smoothly as a tight rear wheel for example can cost you dearly in terms of runtime.
Are you getting these runtimes on a track or on grass/dirt/tarmac?
Ansmann does acouple of budget chargers well capable of fast charging your packs but keep and eye out for chargers with an integrated balancer should you ever want to get lipo batteries.
__________________
|