Yesterday my bullet connectors failed. I suppose I shouldn't be too surprised, since they were perhaps the most under-rated part on the e-bike and they take daily abuse. This connection is made and broken at least twice each day and each time I get a nice big spark as the controller's capacitor chargers. The connecting wires were only 12 gauge so they probably also represented a high resistance connection especially under load. I suppose it was for all those reasons that I really didn't mind being force to upgrade them when they broke.
It seems e-biking upgrades always follow a common pattern. First you buy cheap because you just want to get started and you're thinking it will save you money. Then you start putting on the miles and you have something break. That's when you realize that spending a little extra money up front will save you money and time in the long run and you go ahead and upgrade to the best you can find. 1000's miles later you are still very happy you did it right! Each day I'm forced to drive my car vs. the e-bike cost me at least $10 in fuel. So the $30 I spent on this upgrade was nothing compared to driving the car all week.
So, I upgraded both ends of my battery connection with heavy duty 6-gauge wire and high power connectors. I suppose it's only fitting since I'm carrying around a $1000 + battery that it should have a high quality load carrying connector. Now I've got at least 50A of load handling capacity. I'd recommend this type of setup to anyone with an E-bike once your initial setup fails. I found the connectors and wire at NAPA auto parts. They had the parts in the back though, not out on the shelves. Tell them you need connections for a high power battery setup. These connectors are the kind used in 36V and 48V electric pallet jacks and light duty forklifts. Here's an online source for the connectors http://www.allbatterysalesandservice.com/browse.cfm/4,642.html