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
The 3 mosfets outlined have been shunted. A better shunt could have been connecting B- to P- by a big wire (same as Firewheel shunt). Anyway, after the shunt, no more unexpected power cut, never !
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.
Film closed and taped. An even smaller opening could have been made.
Another TG with smaller BMS, using SMD component.
Aliexpress generic battery BMS (Q1=T1 ; Q2=X1)
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)
Does shunting the BMS hurt the battery in the long run?
No, not on monowheels.
Even if yes, I prefer the battery to be hurt than myself to be hurt.
My generic [Dragonmen Hotwheel] after 6 weeks faceplanted me 3 times – the factory has been anything but helpful to remedy my EUC. I am now too afraid to ride it without fixing the problem.
Consequently, I am trying to decide from the many BMS systems you have shown in your post of June 16 in the forum-electricunicycle.org where I have to place the shunt.
Can you please advise where I shunt from my photo in that forum?
I was unable to add the photo here!!
Sorry to hear about your mishaps, hope you are well.
Shunt as in the attached picture with a thick wire. You’ll see a big difference and have safe rides.
many many thanks for finding, argueing and documenting the bms-shunting- solution. I just made it on the battery in my generic X3 clone, that has the same bms as on your first picture in this post. I feel much more safe now while learning to ride this thing ☺.
I meant the first picture of the generic bms (yellow pcb), not the first in the post – sorry…