소개
We've been saying it for years: Any product that can have embedded electronics, will (eventually) have embedded electronics. Today we have a new cyborg hitting the teardown table: the Xiaomi MiJia QiCycle Folding Electric Bike. This is the first vehicle on our chopping block, so we’re excited to dive into a whole new class of device. Has Xiaomi managed to make the ever-repairable bicycle smarter, without making it a nightmare for DIY tinkering? Let's get rolling on this teardown and find out!
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필요한 것
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Look at you, little mobile friend. Quite stylish from the outside we take a look at the specs:
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250 W, 36 V high-speed motor M108RL from Ananda
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0.21 kWh battery (with 20 NCR18650PF Li-ion cells)
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45 km of biking power on a single charge
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Shimano Nexus 3-speed gear hub
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Torque measurement sensor adjusts power based on your pedaling
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Trip computer combined with controller to provide real-time stats for speed, distance, power etc.
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For those of you not familiar with foldable electric bikes, here's another, the classic, yet analogue Brompton folding bicycle, for comparison. (It's a bit more macro than our usual comparisons.)
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The QiCycle has a smaller wheelbase (870 mm) with smaller tires (16"). The fixed handlebar and saddle max out lower too (bad news, riders over 5'6"/170 cm).
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The built-in bike computer can switch between four power modes and monitors real-time riding data. (And a smartphone app has a ton of info, too).
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Enough talk, lets strip this vehicle down starting with the easiest part: the saddle. Two quick-release clamps later it's free!
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The seat post locks the rear rocker arm in place, so once removed the bike can fold up.
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Next unscrew the fancy folding pedals. This mechanism reduces the overall width of the bike when folded.
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The chain runs outside the rear rocker swing, and has a handy rear chain stretcher, making removal pretty simple.
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The chainring has 52 sprockets whereas the rear hub gear counts 14 sprockets. That gives us a ratio of 1:2.7 in first gear, 1:3.7 in second gear and 1:5 in third gear.
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The chain itself has 96 links. There's no master link for opening the chain but a standard chain tool can pop out any link.
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Taking the crank arms off takes a little preparation, a cover must be removed before you can fit the crank puller on. But after that it pops out like any other bike's crank.
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The next piece of the power conveyance puzzle is the bottom bracket.
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Again we need a standard bike tool—the cartridge bottom bracket tool—to loosen this piece of hardware.
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The rear wheel has a hub roller brake, a style of drum brake. It is operated by hand brake lever so you can backpedal freely.
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We start to fish out the brake cable, but it looks like it's riveted to the hub assembly, and will stay attached at that end.
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So we loosen the bolt holding the hub to the frame and lift out the 16" wheel with its 28 spokes, 3-gear hub and roller brake, and its trailing brake cable...
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Of course we wouldn't be tearing this bike down if it weren't a smart bike. So it's about time we check out the speed sensor.
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The cable connects under the seat then runs along the frame to the (modular) dropout.
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We're able to peel the cable out, and free the sensor assembly.
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Pushing out the small circuit board, we get to the meat of this miracle measurer:
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A Micronas HAL1820A programmable linear hall sensor
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The three wire system is connected with a simple JST connector, not solder. Now that's what we call modular.
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Back to something more mechanical we unmount the front brake—a standard dual-pivot side-pull caliper brake.
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To find more electronic components we aim for the front wheel with its hub gear motor.
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A simple tug disconnects the hub motor cable so we can finally take out the front wheel.
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With the cover lid unscrewed we can push out the source of rotary motion and discover a small circular board behind the rear cover of the motor.
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Besides distributing power it also has three sensors (every fourth coil) for measuring the speed.
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The three gears on the flip side are made of plastic to keep abrasion to a minimum.
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And now, welcome to the middle of the teardown.
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We stripped the QiCycle of most of its bike parts. The aluminum skeleton we are left with weighs 5.5 kg which is over a third of the overall weight.
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We go ahead and pull the main plug from the top tube, enabling us to extract the nervous system linking all the electronic components.
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Only 4 Torx screws hold the cover of the bike computer and the 160×128 pixel TFT screen is attached with a simple ZIF connector.
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On the flip side of the board we find the following chips:
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MediaTek MT6261A ARM processor
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Microchip PIC16LF1518-I/MV PIC controller
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CSR 1010D A05U bluetooth smart IC for lighting
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Texas Instruments TPS259240 eFuse with over voltage protection
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Winbond 25Q128FV 128 Mb serial flash memory
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STMicroelectronics accelerometer
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We saved the best, or at least the most power-ful, for last—the battery tube!
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The tube can be removed single-handedly, with just the push of a button, and can be charged in 3 hours with the 5-pin connection on the side.
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A good amount of the bike's weight is this battery—it weighs 1.46 kg, fully charged of course. ;)
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The bike's battery capacity measures in at 5800mAh (208.8Wh). For your pointless comparison of the day, that's more than 5 iPad Pro 12.9"!
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We begin to pry out the rear light, a cable keeps it in place, but it does give us access to some hidden screws. This in turn grants us access to the internals.
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This massive umbilical leads from the charging port to the batteries and the BMS (Battery Management System) at the other end, and an LED board behind the rear light.
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We peel out said circuit board and discover some secrets. This guy controls the rear LED array, as well as some status LEDs along the top of the tube (probably to indicate battery activity).
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The main battery compartment is a tough nut to crack. Five screws (hidden by some hard to pry off covers) aren't all that hold this case together.
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As we finally succeed with some gentle heating and "good vibrations" we snap open the case, breaking one-time-use clips in the process. Bad news for battery cell replacements.
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We finally reach the prize: 20 Panasonic NCR18650PF Li-Ion batteries! Panasonic is a good (safe) brand, so recharging should be a breeze, even if individual replacement won't be.
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The battery pack also has a battery management system (BMS) circuit board.
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The board is packed with lots of resistors. What sticks out are these components:
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An ATMEL MEGA 328P Battery Management MCU
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Ablic (formerly Seiko Instruments) S-1142B33H-E6T2U 200 mA LDO regulator
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FL12.000 12 MHz quartz crystal oscillator
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On the flip side we find these:
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Magnachip MDU1931 single n-channel trench MOSFET (x4)
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RS2M rectifier
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braincontrol unit is mounted to a handy handle that attaches to the frame with two simple screws. -
Having removed the screws, we can grab the controller unit by the guide rail and slide it right out.
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This bike's brain is a single unit electric bike controller by Ananda, a manufacturer of many electric bike components.
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이 단계에 사용된 도구:Jimmy$7.95
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Of course "single unit" doesn't mean much to us, we dive in past some standard Phillips screws, and work on prying the stubborn casing open.
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We grab a Jimmy and iFixit Opening Tools and try to negotiate–without any success, even when heated.
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We turn our efforts to the side panel, and what we found inside will shock you (people always fall for that, right?)
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Three boards—bridged by an army of pins—are drowned in gobs of yellowish transparent rubber.
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Most of the important components live on the battery pin board, we spy:
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STMicroelectronics STM32100C8 micro controller with an ARM Cortex-M3 32-bit RISC core
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Microchip MCP2003 LIN J2602 Transceiver
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Diodes Incorporated AS358M low-power dual operational amplifiers
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GH17M transistor
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The rest of the goop-covered boards mostly carry capacitors and other passive components.
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- Standard bicycle components and tools are used throughout, making repair more accessible.
- The battery assembly can be removed and replaced with ease.
- The electronic components can be removed without compromising the bike, extending its life and making recycling easier.
- The seatpost, frame, and front hub motor are nonstandard, making a replacement a bit more difficult when the manufacturer does not offer them.
- The battery pack is a complex assembly that makes for wasteful replacement when individual components fail.
최종 의견
수리 용이성 점수


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댓글 131개
My axiomi qicycle seat post keeps slipping down despite locking d 2 release clamps tightly. Caused a fall from d bike as d seat post slipped and hit d ground jamming d moving bike. How to tighten d 2 clamps to ensure no slippage especially cycling at a higher speed?
Thanks
The quick release clamps can be adjusted by using the bolt on the opposite side of the handle and tightened by closing the handle. The QiCycle is constructed for max 100kg weight. You may also try cleaning the seat post for a better grip (maybe it got a little greasy during the assembly).
I am wondering if the two saddle clamps can be replaced. And if so where to find them? Help very much appreciated :).
The saddle clamps should be replaceable with standard quick release clamps of the correct size. Depending on the design the handle might not be curved like the original one and therefore stand off a little bit.