The controller does not have regulated voltage and I'm not aware of any ebike that does. Someone will correct me if I'm wrong. The behavior you describe is typical of bikes at low voltage and this is the result you'll get every time. It's not bad design, it's typical design. I'm concerned that you will harm your battery, running it too low like that just to see what happens. With a 52 volt system, by the time you hit 46 volts you will notice a distinct drop in performance and really shouldn't go much lower than that if you can help it. 46 volts is just over 20% state of charge, which is the practical limit for these batteries. @Ravi Kempaiah would you care to chime in? (In case you don't know Ravi, he's a PhD student in this kind of technology and holds a world record for long-distance ebiking, so pretty knowledgeable from both the scientific and the practical side.)The Battery; I've now put 86 km on a single charge of the battery (single trip), voltage was 45.6V under load. The bike was packed carrying an extra 13Ah battery, and some gear of a similar weight. The bike didn't quit, but at/under 46V the bike performs poorly compared to higher voltages. Noticeable pulsing when power is required, throttle unable to give the typical boost. It's like the 750W motor turns into a 300-350W motor. I don't have the time to drain the battery more as i need it recharged for another long trip, but I'm going to make a point of running it down further to observe the behavior. Right now I'm a little disappointed in this behavior, the controller/motor are not well designed for when the battery gets low.