I went for a long test drive last night and broke the Model S distance record on Teslafi by clocking up 658km / 409mi in just over 9 hours: TeslaFi.com Shared Drive
The purpose of this experiment was to figure out how far I could push the range by going at an "ultra long range cruise speed". This is useful when travelling in Australia, because it's a big country, with few charging stations when away from the populated east and south coast between Brisbane, Sydney, and Melbourne. After this test, I can now confidently say that leaving on a full charge, I can easily break 600km / 373 mi range without getting nervous about it by simply sticking to at or below 80 km/h / 50 mph speeds - when using autopilot that's not even too fatiguing either.
Given most of Australia is relatively flat, elevation changes account for a small amount of range loss only and really only needs to be factored in when going to a handful of places. To make this realistic, I refrained from going dangerously or inconveniently slow and kept my travel speed between 70 - 80 km/h (43 - 50 mph) - but that still required doing the test overnight so as to avoid slowing down too much other traffic in the Sydney area where I live. Highway speed limits where I was driving were between 80 - 110 km/h (50 - 68 mph). I also wanted to retain most electrical consumer essentials such as entertainment, autopilot, lights, and air blowing into the cabin (albeit with the HVAC system off). I recorded battery metrics in the process using a the tesLAX app and some custom scripts I wrote to log the data. I was particularly interested in figuring out how much buffer really is in my battery pack. The battery management system (BMS) reports a percentage that is different from the one display to the user. As power drains from the battery, these percentages differ significantly, with the BMS reporting 5.7% left when the car reports 0%. This translates into an additional 30km / 18mi of available range until the batteries are really flat. And by flat, I mean they're at 2.8-ish V, which is the point where the Li-ion cells can suffer damage when pushed below. I stopped my drive when they reached 3.0V, but as can be seen from BMS% vs Voltage plot, the BMS percentage reported looks to be set to show 0% when the still safe limit of 2.8V has been reached.
The upshot is simple: Tesla are not hiding a huge amount of range in the battery pack, and what matters most is the speed you're doing. No surprises there really, considering air resistance increases with the square of the velocity. But when getting below 20% battery, things are going decidedly non-linear and you do in fact have a fair bit more range in the batteries than the car's computers want you to believe.
The purpose of this experiment was to figure out how far I could push the range by going at an "ultra long range cruise speed". This is useful when travelling in Australia, because it's a big country, with few charging stations when away from the populated east and south coast between Brisbane, Sydney, and Melbourne. After this test, I can now confidently say that leaving on a full charge, I can easily break 600km / 373 mi range without getting nervous about it by simply sticking to at or below 80 km/h / 50 mph speeds - when using autopilot that's not even too fatiguing either.
Given most of Australia is relatively flat, elevation changes account for a small amount of range loss only and really only needs to be factored in when going to a handful of places. To make this realistic, I refrained from going dangerously or inconveniently slow and kept my travel speed between 70 - 80 km/h (43 - 50 mph) - but that still required doing the test overnight so as to avoid slowing down too much other traffic in the Sydney area where I live. Highway speed limits where I was driving were between 80 - 110 km/h (50 - 68 mph). I also wanted to retain most electrical consumer essentials such as entertainment, autopilot, lights, and air blowing into the cabin (albeit with the HVAC system off). I recorded battery metrics in the process using a the tesLAX app and some custom scripts I wrote to log the data. I was particularly interested in figuring out how much buffer really is in my battery pack. The battery management system (BMS) reports a percentage that is different from the one display to the user. As power drains from the battery, these percentages differ significantly, with the BMS reporting 5.7% left when the car reports 0%. This translates into an additional 30km / 18mi of available range until the batteries are really flat. And by flat, I mean they're at 2.8-ish V, which is the point where the Li-ion cells can suffer damage when pushed below. I stopped my drive when they reached 3.0V, but as can be seen from BMS% vs Voltage plot, the BMS percentage reported looks to be set to show 0% when the still safe limit of 2.8V has been reached.
The upshot is simple: Tesla are not hiding a huge amount of range in the battery pack, and what matters most is the speed you're doing. No surprises there really, considering air resistance increases with the square of the velocity. But when getting below 20% battery, things are going decidedly non-linear and you do in fact have a fair bit more range in the batteries than the car's computers want you to believe.
