The Firewheel is a tremendously powerfull 16″ wheel. So even the 520Wh model with a big 16S4P battery, a strong acceleration or a steep road can cause enough current rush and voltage sag to trigger a power cut. The wheeler had a hurt shoulder that needed several visits to the doctor and a specialist, quite a costly wheel, right ?
I myself had a power cut on my 260Wh Firewheel, at a miraculously low speed (I normally cruise at 25 km/h) and no harm but that left me stranded miles from home. The incident, which could have been harmfull, initiated my research of the BMS problem and solution. I had two sudden cutoff before on my TG, but didn’t know where the problem comes from.
B- shunted to P- by a big wire. Route the wire like in the picture to avoid adding thickness to the battery pack. Note that the B- wire here is red instead of the usual black color code for negative pole, an occurrence of lack of care (other Firewheel BMSs have the right color, ie black) which can be very misleading.
The Dolphin is a rather powerfull wheel, with speeds over 20km/h so the probability of power cut because of high currents and voltage sag is high. Three left mosfet shunted.
An X3 clone with a nice housing with an integrated trolly and a silly pair of rollers. Even with two battery packs in parallel, a sudden power cut had left the wheeler a hurting shoulder, wrist and rib for weeks. Power cuts happen quite often, so a shunt is absolutely necessary.
Source : GD3771730 from http://trottinetteselectriques.heberg-forum.fr
TG is a nice X3 generic clone, with external openings and a high quality plastic housing, much stronger than the original Airwheel X3. It cheap and widely available from big internet vendors like DX, Banggood, Focalprice… Problem is the power cut occurs very often, even on TG with high battery capacity 340Wh.
Another generic wheel BMS. Shunt B- to P-
BMS of noname LiIon 174Wh pack. Shunt = B- shorted to P-. Note the absence of the protection diode on the charge paths like on Gotway wheels, meaning that high voltage will be present at the wheel’s charge port, so beware !
A 350W generic with 14″ wheel. Electronic compartments opened from inside like the original Airwheel X3 (bad point). The power cut (and faceplant) happens when the level is down to 2 leds on the 4 led scale. It was on a new wheel so probably a sign of faulty battery cell(s) but nonetheless evidence that the BMS needs to be shunted.
Source Aurita, from forum.electricunicycle.org (click image to zoom)