Yamaha Power Assist Bicycles - how to enable the motor to run?

[legacy]

Yamaha Power Assist Bicycle


the cables to the motor


the connector from the motor to the battery: only the red, black, and yellow wires are used


digital controller


a pic of the motor


so, I have recently found the above bicycle for sale at a super low price, but there is a reason for that: it misses the battery pack, and the connector is not very good. It sounds like the previous owner just wanted to shift it out of the door.
Anyway, paid 100 Euro for the bicycle, and now I have to understand how to make it work.

First of all, the battery pack was at 4A@25.2V, and there are three wires from the package to the motor engine: red, black, and yellow. The blue and white wires are only used by the battery charger.

I don't know what the yellow wire is for, it looks like a sort of "power good" signal or "battery good" signal, and without that wire connected, the controller on the bicycle handlebar says the battery is no good, and it doesn't enable the motor to run, even if it takes the energy from the external PSU rather than a battery pack.

Since I don't have an original battery package I can't try to investigate or reverse engineering signals.

Do you happen by any chance happen to know what is the yellow wire for? And which kind of signal (e.g. 5V DC, higher?) does the motor-box need to receive in order to be enabled?


Thanks in advance 

[NiHaoMike]

Probably just a thermistor to detect if the battery is getting too hot, especially for something quite low end. Try a 10k or 100k resistor to ground.

[The Soulman]

Probably just a thermistor to detect if the battery is getting too hot, especially for something quite low end. Try a 10k or 100k resistor to ground.

From my experience with ebikes and nimh battery packs I can say that is most likely it.

[digsys]

In some countries, like OZ, the controller HAS to see pulses coming in from the pedals, usually 1-2KM/hr, before it will allow the motor to come in. Just a FYI

[m3vuv]

better asking the question on endlesphere.com forums.

[Zero999]

First of all, the battery pack was at 4A@25.2V, and there are three wires from the package to the motor engine: red, black, and yellow. The blue and white wires are only used by the battery charger.

I know I'm being picky but batteries are specified in Amp hours, i.e. Ah, not Amps.

A fully charged 4Ah battery will be able to provide 4A for an hour, or 1A for 4 hours before running completely flat.

The maximum battery discharge current might be higher, but it's not normally given on the name plate.

[legacy]

digital controller

Probably just a thermistor to detect if the battery is getting too hot, especially for something quite low end. Try a 10k or 100k resistor to ground.

From my experience with ebikes and nimh battery packs I can say that is most likely it.

thanks, guy 


just a doubt, look at the picture, it seems the digital controller on the bicycle handlebar is able to show if the battery is at { 1/4, 2/4, 3/4, 4/4 } of its charge: how can show it?

I mean by which signals? directly from the 25.2V on the red and black cables (so, from a cabling done inside the motor), or *maybe* by the yellow wire?

The original battery was LiPo: how do you measure the charge status? (how much energy the battery can still provide)


When I switch-On the digital controller on the bicycle handlebar (by giving 25.2V on the red and black cable) I see all the four Leds power down, that means 0/4 of charge 

[legacy]

know I'm being picky but

it's written on the plastic of the battery connector on the bicycle frame where the battery goes mounted, besides sentences written in Japanese: it explicitly says 25.2V and 4A, which is also the value of the fuse on the connector as the maximum current deliverable.

[legacy]

as a sort of lipo fuel gauge, it would be interesting to understand how the digital controller (or the circuit built-in with the battery package) estimates the approximate how much ‘fuel’ is left in the tank, and represents it by turning on the four LEDs, and - possibly - also it can enable or disable the motor engine accordingly.

My pure speculation, I don't believe it needs to be accurate at all, p.e. four simple signal LEDs which warns you about low battery level 

[Zero999]

know I'm being picky but

it's written on the plastic of the battery connector on the bicycle frame where the battery goes mounted, besides sentences written in Japanese: it explicitly says 25.2V and 4A, which is also the value of the fuse on the connector as the maximum current deliverable.

Oh I see, then unless it's a typo, it will be the voltage rating of the motor and the current consumption, not the battery capacity.

[MK14]

I would have guessed the battery amp/hour would be around 20 amp/hour.

I don't know what exact model you have. But in general  ...

Every model in the Yamaha Power Assist Bicycles lineup is powered by a 500 Watt-hour Lithium-ion battery pack with a 36V output that recharges in just four hours.

Which would be around 20 Amp/hour if it was 25 Volts. Could be different, as yours could be a much older model.

https://globenewswire.com/news-release/2018/03/27/1453898/0/en/Yamaha-Announces-Power-Assist-Electric-Bicycle-Full-Specs-and-Pricing.html

[legacy]

Could be different, as yours could be a much older model

Probably.

But I can't tell you more since I am not in contact with the previous owner 


anyway, I am willing to open the motor-block, more pics will follow ... 

[m3vuv]

how many wires go into the motor 2/3 or 8?,and the colors most brushless motors are 3 phase,the phase wires are blue yellow and green,then you sometimes have hall sensor wires,normaly a thin red,blue,green,yellow and black,if the motor has 3 wires,its brushless,8 its brushless with hall sensors,and just 2 wires its a brushed motor,hope this helps,cheers m3vuv.

[NiHaoMike]

100W doesn't sound like much when cheap Walmart specials are 300W or more nowadays. It was probably designed when battery technology was much less advanced and increasing the power would give too little range.

[legacy]

the motor engine


let's open the motor


brushless with 3 phases


sensor for the bicycle crank


an explode of the engine


the controller (WTF is that?)

[legacy]

so, the motor has a digital controller (DSP?), unfortunately, I can't read what is written on the top of the big squared black chip, but I really wonder WHY there are so many wires going to the interface-box (the thing with LEDs and button) on the bicycle handlebar

too many wires, really too many! one of them, the grey one is connected to the yellow wire from the battery (NTC?!?!?); and for sure a subset of these wires are for the gear.

but why the digital controller that controls the brushless doesn't just use an RS422 or RS485 to communicate with what clearly appears like an interface? It everything is embedded with motor box, why do so many wires need to go outside?

[legacy]

as proof of concept, is it anything like this for the battery?

[legacy]

100W doesn't sound like much

Yup, and probably this was the reason why the bicycle needed to go and the dude shifted it out for sale for a ridiculous price. It makes sense 

[perieanuo]

as proof of concept, is it anything like this for the battery?

Exactly,you have a battery controller (bms) for 4 elements,the controller balance the charge to every element separated.ntc is more often 10k or 100k .


Envoyé de mon iPad en utilisant Tapatalk

[legacy]

I added a 100Kohm resistor between the yellow wire and ground, but no progress

[legacy]

other ideas? tips?

[NiHaoMike]

Try 10k, which is the more common kind of NTC anyways.