Monthly Archives: July 2015

King-Song / Gotway comparison

King Song is a promising brand that deserves recognition given the incredibly neat finish of its wheels:  coated electronic board (nothing on the Gotway), tightly sealed compartments, mainboard aluminium heat sink thermally facing the wheel to greatly increase heat dissipation,  comfortable foam leg rest. Ergonomically, I appreciate the following points which are desperately needed on the Gotway: not thicker than a Solowheel therefore much more comfortable for the legs, removable battery, fanless and thus totally silent charger, head and rear lights, USB socket 5V / 2A to recharge GPS, smartphone, flashlight, camera …

King Song wheels are copies of Gotways as to the electronics and the motor, so the riding performance is that of Gotways.
Here is a comparison of the mainboards of the two 14 ” wheels, they both share many identical components.

1: STM32 Cortex F103C8T uP (48 pins)
2: step down power converter
3: current sensor
4: gyroscop IC
5: mosfet driver
6: input capacitor
7: additional switching power supply for the USB connector (and lights?)
8: Unknown

Mainboard King Song 14 “ Motherboard King Song 14

Mainboard Gotway 14 “ Motherboard Gotway 14

Other infos:

  1. Images & comments: http://www.znphc.com/201506/2789.html (useGoogle Translate)
  2. Quick Review: http://forum.electricunicycle.org/topic/714-kingsong-14c-first-impressions/

Airwheel Q3 & clones, how to double battery

Mod by Smallexis from trottinetteselectriques.heberg-forum.fr

The Airwheels Q3 and its clones has big housing and a lot of internal space for a big battery pack. To double the capacity of the anemic original pack from 130Wh to 260Wh, Alexis has soldered individual cells recovered from an spare pack in parallel with existing cells, one by one. He has also shunted the BMS, of course.

Continue reading

Airwheel – BMS Shunt

Airwheel Q3

The Airwheel Q3 260wh has two paralleled 130Wh battery packs, each with its own  BMS (battery management system). Even this setup, if not shunted, is still dangerous, tatane33 has had a fractured jaw because of a sudden power cut on his Q3. Peppuzzo has shunted both BMS for added security. He wants a fail safe wheel, which is understandable even if shunting just one BMS is probably enough. Continue reading

BMS, how to make your wheel safer

Most unicycles use bicycles’ BMS (Battery Management System) which has a overdischarge cut-off circuit (T1) to prevent the battery from discharging under the LiIon recommanded voltage. It’s a feature usefull for off-the-shelf bicycles’ batteries but for monocycles, it’s
1) unecessary since the mainboard deals quite well with voltage warning
2) utterly, incredibly stupid since a cutoff by the BMS results in a faceplant for the rider. In other words, the wheel’s designer prefers to protect the battery by hurting the user!!! Many many users have been harmed, especially when the wheel is cold (under 10°C), since the batteries’ internal resistance increases and triggers the cut-off more easily. Continue reading

Keep the Gotway quiet

The buzzer on my Gotway 14″ MCM 2S 340Wh is very loud. It’s a piezzo device, powered by a 25% duty cycle 3.3 khz square signal. The signal’s amplitude is 65V (the battery voltage !), no wonder it’s loud, and super duper annoying for you and certainly much more for pedestrians.

Unfortunately, as it has been said at length on the forum, the buzzer can’t be cut off because the GW has no tactile warning like tilt-back or vibrations on any other wheels. Without the beeping, you can overspeed (which can happens even at… 6km/h when the battery is near flat) and then, the wheel WILL shut the power down and throw you off. Yeah, as unbelievably stupid as it seems, it’s totally true : the wheel shuts the power down when riding to… protect you, nice logic, no ?

To reduce the volume and to make a Gotway ride more bearable, I don’t do the 100 Kohm potiometer-series-connected mod, it’s has been out there since the Gotway exists as a testimony of the super duper annoying buzzer (Gotway, please, do something !!!).

Here is my way to tone down the buzzer : a screw.

gotway_buzzer