I have a traxxas rustler and just bought some duratrax 8.4v 5000mah batteries. They only have about 8-10 runs on them and i went to run one and i knew it was at 100%. It runs great for about 5 muinets then it acts like it is dead, but when i plug it in to my venom peak charger i only takes 300mah then it stops. I was wondering if I could put it on a discharg/charge cycle to restore it but i didn't yet. I want to know if it would be a good idea to do that or if their is anything else i could do.

please help me and thanks in advance.

When you charged it and it only took 300mah, did the batt get hot? If not, its prob a false peak - the charger thinks it see the small peak voltage rise and thinks the batt is full so it terminates the charge and its really too early.

Just reset the charger and try again. New batts seem to be bad about false peaking and you might have to do this several times to get a full charge. Some chargers have a peak delay time so you can tell teh charger to ignore anything it thinks is a peak for 10 or however long you think is necessary so the batt doesn't false peak. Unfortunately the Venom charger doesn't have this so you just have to keep resetting it back to charging. The batt should get to ~120F or so when it truly peaks, so until it gets that hot, just keep trying.

As batt gets older it won't do this as much.

maybe you should try to fully discharge the battery and then charge it. i do that to my batteries once a month just for maintenance.