Surface recommends lowering assist level to 1 or 2, when battery indicator shows capacity getting low. With torque sensing you can get more fluctuation in voltage, as capacity drops, since it's responding to foot pressure (rider effort) rather than cadence. The fluctuation may be causing the trigger on low voltage. Staying at a lower speed, which decreases wind resistance, and not demanding as much assist, will help you get more range out of it when you get to the capacity level or voltage level being measured becomes an issue. It's in part the idiosyncrasies of not only how they are measuring voltage (and what can be accomplished at this price point which is unusual to see a torque sensor) and how they are accomplishing the torque sensing in general. It's my understanding Modifications to how they are measuring torque will be made for product sold after August. For mid drives which are generally more sophisticated (and higher priced), they using multiple forms of sensing, and different ways to accomplish torque sensing, so it's not a simple matter of saying the method used by Surface or others on hub drives is 'inferior' or that you need to buy a high priced bike to get a better outcome. Surface will also be helping itself by finally offering a larger battery capacity at 14 Ah, versus the current only available size (up to now), of 10 Ah. They may be able to change how they measure voltage as well, but not sure that is necessary with the other product improvements. It's a learning curve for all of these ebike Oems, especially ones like Surface or Juiced who push hard to give more features, and better performance, at lower price points than the competition. Ebikes have come a LONG way, from even a few years ago, and the improvements in a lot of cases are light years of what they were 10 years ago, or before we even had access to lithium batteries at affordable prices. You become more accepting and appreciative the more models and designs you get exposed to, and especially when a lot of brands keep offering really expensive models, while a handful of these brands are working in the lower price ranges, yet still pushing the technology envelope to give more to the customer. My two cents anyway. The tariffs have made this even tougher to accomplish. Its deepened my respect for these firms like Surface, Juiced, Blix, Ariel, and now more recently Aventon to name a few.
