Hill climbing ability of the MiniPRO

[trevmar]

We live in an area where there are lots of steep climbs. They are not really steep, but they have given me problems with unexpected push-back from day 1 with the MiniPRO. There is little data available on exactly how much power the MiniPRO motors can deliver, and how this translates into speed on either flat or sloping surfaces. The best source of information was shown to me by JoJo, it is a blog about the MiniPRO development cycle at Ninebot: http://bbs.ninebot.cn/forum.php?mod=viewthread&tid=4100

Google translate produces this for a key section of the blog: "We have done a lot of power test experiments. The results show that when the weight of 100kg people climbs 15 degrees at 5-6kmh, the power demand of the whole vehicle will reach 400 watts or more. If the slope is slightly accelerated, the power will rise to 800 watts. The tester weighing 120kg may reach 500 watts when driving at 20kmh, and the output power of the car may reach 1000 watts to 1200 watts when it accelerates to 30kmh."

So, I read that as saying a 120kg person riding on flat ground will need 500W of motor power to reach 20Km/h, and 1000W-1200W to reach 30Km/h. The continuous limit of the motors is "350w / short time 1050W, and the maximum torque of a single motor is .. more than 35Nm." So the firmware has to decide when to start pushback whenever the continuous output power being used is greater than 700W, or else the motors will overheat,and likely the battery pack too. Here is the 19 degrees street that the MiniPRO design team used as their reference for the "World's Steepest Street"

But they eventually decided on planning for a 15 degree slope, less steep than this one. They planned  "100kg people climbs 15 degrees at 5-6kmh, the power demand of the whole vehicle will reach 400 watts or more. If the slope is slightly accelerated, the power will rise to 800 watts."  This represents the totality of the engineering specifications I have been able to find about the MiniPRO

When I measure myself, a new N3M320 MiniPRO which has not yet done 50Km starts to push-back at around 9Km/h on the steepest steady hill I have around here, which is 6.5 degrees. I weigh 94Kg (in riding boots). I see no difference between firmwares 1.1.7 and 1.1.9 except that 1.1.9 has the gentlest pushback cycle (it beeps a warning before making you jump off ). With 1.4.1 it is tough to even reach 9Km/h because it is continually adjusting the push-back point.

An N3M260 which has long-ago reached its 50Km transition can reach 11-12 Km/h (with v1.1.9 FW) before beeping and starting kickback. The max speed is the same whether I am using the smaller 243Wh or the full 310Wh battery.

So there clearly is a safety margin which the firmware holds in reserve to try and preserve vehicle integrity. Yet how the firmware implements this push-back reserve is (IMO) flawed, as it also seems to limit the ability of the MiniPRO to handle potholes and pebbles until the 50Km mark is reached. I will be watching very carefully as my new N3M320 reaches that target, and then do a complete reassessment of the vehicle's hill-climbing ability...

Finally, I note that the older N3M260 had the 90/65-6.5 knobbly off-road tyres fitted, running at 15psi, while the new N3M320 has slightly smaller 'off-road' tyres, which should have given it an edge in torque, but didn't. Only when I get to 50Km will I be able to decide how the firmware handles safety reserves when larger tyres are fitted - there is a possibility that the slope climbing speed limit is set by a firmware algorithm, and not by the motor power exceeding 700W.

Please share any data and experiences you have had negotiating slopes with the MiniPRO.

[68bugboy]

I have noticed since I put the 90/65 street tires on my Minipro

that when climbing hills I get tilt back earlier than when stock

tires were mounted.

Not sure why.

[trevmar]

15 minutes ago, 68bugboy said:

I have noticed since I put the 90/65 street tires on my Minipro

that when climbing hills I get tilt back earlier

The motors put out a torque, the maximum torque is fixed by the hardware and battery charge level. When the tyre is a larger diameter, and torque is constant, the force is less at the road surface than with the smaller tyre. So I would expect that if your pushback is being initiated by the motors complaining, then putting on larger tyres would not necessarily give a speed increase. But I don't think any of us really understand how the firmware calculates the rider's weight, there must be some torque-related algorithm in play.  I suspect that larger tyres would make the miniPRO think a heavier rider is aboard (when it calculates the wheel rotations (distance) and compares it to the electric current demanded (torque)).

[trevmar]

I just reached the "run-in" 50Km of one of my new N3M320 MiniPRO by riding it around the block continuously for several hours. I noticed a small speed increase before push-back, and when I went to my 1-in-8 test hill I confirmed that tilt-back speed had increased from 9Km/h to 10.5Km/h (approx). Both my run-in MiniPRO are both doing the same speed on that test incline now It isn't fast enough, IMO. Not compared with the data given by the Ninebot engineers in their blog. They say:

"when the weight of 100kg people climbs 15 degrees at 5-6kmh, the power demand of the whole vehicle will reach 400 watts or more. If the slope is slightly accelerated, the power will rise to 800 watts"

yet here I find that a 94Kg rider on an 800W MiniPRO climbs 6.5 degrees at a maximum 10Km/h before pushback. My slope is 1-in-8 rather than their 1-in-4, my rough maths say that something is still being throttled back in my 1.1.9 firmware.