This proves the point that mid drives just not are as 'efficient' (i.e. lots of distance) as so many want to claim. To be fair, yes they are 'efficient' for getting the most out of a particular size battery and motor sized at a certain wattage, but don't confuse that with getting lots of 'distance' when you have a lot of weight, a non horizontal (i.e. no grade ride), and a rider who probably at the age of 60 may not have the physical prowess or lung capacity he/she once had at a younger age. With those kinds of climbs, and the terrain you are on, you really need to have a 48 volt system, and probably at least a 14 AH battery at 48 volts, to get the distance you desire. Most mid drives are rated at 250 watts nominal, sometimes as high as 350 watts, but they are attempting to do 'magic' at 36 volts in terms of power transferred. Making something as 'efficient' as a "Prius" for example, ain't gonna do very well if its pulling a 1000 lb trailer. Granted the rider isn't that heavy, but its an analogy, to illustrate you can only do so much with 250 watts and 36 volts. It ain't a lot of 'power'. For example, when you are on mostly flat and smooth terrain, these 'magic' bikes use both internal gearing, and lots of 'ratios' to get as much power to the wheel as possible. But at such low voltages, and with 250 watts, you just are not going to be able to go very far, even if you have a 17 ah battery, when you have any kind of grade. Your wattage draw, and power, increases exponentially as a function of the grade you are on, (and also with wind resistance) and if your motor is only designed for 250 watts, and 36 volts, there is going to be a definitive limit on what will be allowed by the controller and electronics to pass through the windings. 200 lbs is a lot of weight to pull up ANY grade, and while a 250 watt mid drive, geared appropriately will do better than a 250 watt hub drive, with your application, and probably your physical effort, the situation is putting a lot of the requirement on the motor. For example, I know a gal who is a regular bike rider, in awesome shape, and she can go 60 miles on the same battery and motor, that most people only get 35 miles. She says she feels like she is barely 'peddling' and she feels the motor is doing a lot, but its her own strength she is not realizing how much is contributing to the ride. She's 'generating' a lot more watts than an average or out of shape rider due to her leg strength, and being in shape, and great lung capacity.
For your situation, quite simply, I'd get away from any mid drive motor, go with an ebike that has a 48 volt system, and at least 500 watts, and a battery that has at least 14 AH at the 48 volts. (which by the way, has more energy storage than a battery that is 14 AH at only 36 volts. Amp rating x Volts gives you total watt hours.). I'd also consider an e-bike that has more gears than the standard mid drive can provide, since most like Bosch or Brose, have only one front sprocket (chain ring) and usually only up to 11 speeds in the rear depending on the bike. (though Yamaha is coming out with their own ebike models this month, that does have two front chain rings, allowing for more gears, more ratios, better leverage, and better ability to extend distance for a given wattage and battery size. Its still 36 volts though which is a disappointment in my opinion.)
As background - I'm not just throwing this stuff out there to start any arguments amongst the forum - I'm a degreed M.E. , and 34+ years in the energy technology, and power space, having worked with motors, batteries, and so on, and unfortunately I've witnessed is a lot of mis-understanding in this ebike space about how power transfer works, and what motors can actually do, what watts actually means, torque means, etc etc. Watts and Voltage can't be cheated folks, and anyone who claims they can produce x amount of torque, and if you believe that will result in the 'same level' of power available to be applied to the road on a 36 volt vs a 48 Volt system, (even if they have the same 'torque rating) then you are either needing some fundamental schooling in the world of physics, or you are being lulled into believing some mis-guided manufacturer hype about what their motors can do. As Tim (the tool man) Taylor used to grunt = WE NEED MORE POWER. Thats going to apply when you have hills and any grade. Its that simple. That means more watts AND more volts folks, and that's what you'll need for stated your application (ride and grade) and your age, physical shape, as well as a larger battery.
Unfortunately there the math of this, and the physics don't lie. Just finding a larger capacity (AmpHour) battery alone, and staying at 36 volts, isn't going to help you as much as one would think. By the way, a 48 Volt system will also operate 'more efficiently' than 36 volts, and also allow the motor to stay in the best portion of its own power curve, assuming the OEM has applied it properly with the right bike and gearing system.
P.S. Some of these 130 lb (when wet with a parka on) reviewers need to carry a 70 lb sack of cement on their rides, and then tell us all 'how much power' they feel out of these 250 watt mid-drives that they say have so much 'torque'. Its always good for a chuckle or two listening to the discussions and 'comparisons'. On these mid drives, with a small chain ring up front, its easy to claim a higher torque rating, but in the whole scheme of things, its a irrelevent value by itself unless you are comparing apples to apples, and comparing same motor power levels (watts), same set of voltages, and same size controllers that manage the amps, same size chain ring and gearing, what cadence you are comparing, etc. etc. (in otherwords a 50 nm 'torque' rating at a rear hub with a 500 watt motor running at 48 volts, is NOT the same as 50 nm 'torque rating' at the crank with a small chain ring and only a 250 watt, 36 volt motor. So in the end, when choosing an ebike, its wise to simply not use any torque rating as a comparison measure. Its European ebike marketing 'hoo haa' folks. ) Personally, if at all possible, I'd rent an ebike with a higher wattage motor, and higher voltage motor, and try it out on your ride, to see if it will do what you desire, before spending any more time guessing at what ebike you might want or need. Best wishes !
