[aintgotthis]

If you have 50.4v in the pack, you should have lots of juice. Sounds like you have a battery going bad and not letting the power go through it. The only way you can find it without a discharger is to hook a volt meter to a battery and take it for a drive. Keep changing batteries until you find the one dropping way way down in voltage. I've seen them go as low as 1 to 2 volts whil the others are at 8v. Be very careful around those batteries. When one goes bad like that they can gas off badly creating a very high explosion risk.