Brompton q70 motor

[pears_91]

Hi
I'm trying to convert my Brompton to electric and wonder if anyone can help. I have the motor/wheel turning, but it is not providing enough power to pull when it is in contact with the floor.

I have attached the wiring information for the controller I have.. and it is a Q70 250watt motor, I purchased from BMS battery.

Currently I have several wires not connected to anything as I am not using the hall sensor PAS LED etc... I just have the power leads in and out of controller connected, the throttle and have connected the ignition lock cable (blue with red) in the LED wires. That is basically it..

Much appreciated if anyone can help and I'm happy to answer questions if anyone else interested to convert Brompton from what little I do know and have learnt during my first time converting to ebike. I have made my battery pack from scratch, although my spot welding was not very successful, I am pretty sure it's ok for this time but looks a mess, I'd also be interested to hear any recommendations for spot welders..

Best wishes,, rich

Richard

 

[saneagle]

Those motors are a bit tricky to run sensorless. Is yours a sensored motor? If so, it would work better with a normal KT controller for sensored motors if you want an LCD, otherwise a KU63.

The only thing I can suggest is to unmatch the three motor phase wires. If you swap one pair, it'll go backwards, so then additionally swap the other pair to make it go the correct way, then see if it gives better timing. Try all forward combinations.

 

[pears_91]

It is a motor that can be sensor or sensorless it says.

I won't use an LCD for the time being if I can run it without, perhaps I'll think about adding in future though, I'm not sure what the LCD's show you tbh I've not looked into it much yet,, I'm hoping to just get the bike running with bare minimum initially.

These areany wires I haven't connected to anything so before I try a different controller I'll double check my wiring to make sure I didn't need to connect any other wires on the LSW 675 controler that I currently have not used, such as PAS, break wires, speed sensor wires.. for example when I first tried it I didn't realize there was an ignition lock that I needed to connect before it would work at all... once connected it it running but very low torque.

Ill try switching the sequence of my motor connections, I can measure the voltage across the power wires going to the motor.. I assume I should be able to measure the full 36v with the throttle fully open?

 

[Benjahmin]

It's not a matter of voltage but the timing of the voltage pulse that is sent to the motor and anyway the pulse is far to short to register on a dvm. Running sensorless makes this timing more tricky/less accurate.

 

[Woosh]

The Lishui controller with default firmware can't run the Q70 properly.
Also, 18A is too much for the Q70, it needs to be limited to 14A-15A.

 

[StuartsProjects]

You do seem to be making the conversion difficult.

I just finished a DIY conversion on a Brompton using a TBK74AD motor. Granted there is not a lot of space on the bars for one of the larger displays, which can cause issues when the Brompton is folded, but the LCD4 display is small, does not get in the way, and is low cost.

The LCD4, together with a KT controller, is more or less a plug and play combination. The display allows you to setup for maximum speed, wheel size, power assist levels etc, well worth the effort to fit.

 

[pears_91]

Woosh,, I checked the spec online and it is 15a limit,, LSW 657 from BMS battery.. granted it does say comparable with q75, 85 and 100 motors,, not the q70,, but I think q70 was an addition to the range so I hoped it was just a case of it didn't exist as the time they wrote this... in terms of watts and volts it matched my spec so I took a chance on it.


I didn't realize you could actually change anything with the LCD.. I was under the impression it was just to display information.. I'll look into this further.

Mainly my reasons for not having one was as you say handle bar space and an extra cable. maybe I could just attach one and throw it in my battery bag.

 

[Woosh]

the Q70 for the Brompton has high speed and high reduction ratio. That explains why it climbs so well despite its small size and weight. The reverse side of the coin is that it does not run well sensorless because the rotor spins so fast making it difficult for the controller's CPU to keep it in sync. The KT route is the best way out.

 

[saneagle]

Your motor either has hall sensors or not. It can't be both. Which of the two is it?

 

[pears_91]

Your motor either has hall sensors or not. It can't be both. Which of the two is it?

The motor itself I don't believe has the sensors built it,, but it states that it is compatible with hall sensors (has the wiring required to connect) or can be used sensorless.

 

[Woosh]

if the motor cable has 9-pin cable, it likely has built in Hall and speed sensors. Your problem is then firmware update.
If the motor cable has 3-pin or 6-pin, then it does not have Hall sensors.

 

[saneagle]

The motor itself I don't believe has the sensors built it,, but it states that it is compatible with hall sensors (has the wiring required to connect) or can be used sensorless.

The motor cannot be compatible with hall sensors. Hall sensors are an absolute condition. it either has them or not. If it has them, you have at least 8 wires in the motor cable or a 9-pin connector. If it doesn't have them, the motor cable has three wires or a three-pin connector. Which do you have? It's important if you want to solve your problem. If your motor doesn't have them, you can't add them - not easily, anyway.

There are two versions of your motor. One has hall sensors and the other doesn't.

 

[pears_91]

The motor cannot be compatible with hall sensors. Hall sensors are an absolute condition. it either has them or not. If it has them, you have at least 8 wires in the motor cable or a 9-pin connector. If it doesn't have them, the motor cable has three wires or a three-pin connector. Which do you have? It's important if you want to solve your problem. If your motor doesn't have them, you can't add them - not easily, anyway.

There are two versions of your motor. One has hall sensors and the other doesn't.

it has 8 wires so it must have hall sensor built in?

I havent connected the 5 wires for hall sensor to anything though

i guess this is the problem .. I dont seem to have anything on my controler to connect them to.

 

[Nealh]

One needs a sensored controller .

 

[saneagle]

it has 8 wires so it must have hall sensor built in?

I havent connected the 5 wires for hall sensor to anything though

i guess this is the problem .. I dont seem to have anything on my controler to connect them to.

You have a sensorless controller and a sensored motor. As I said, the Q70 doesn't work well sensorless, so you need a new controller.

 

[pears_91]

Thanks for you help I'll change it and let you know how it goes.

 

[pears_91]

Wow... that is so much better!

I didn't expect it to be so powerful.
I put the controller compatible with hall sensor, and an led screen to change the power etc.

Brilliant, thanks for the help, I would not have figured that out without the advice.. when it said hall sensor I always thought it was referring to the pedel sensors.. so as I have a throttle I didn't want that.

Anyway.. very happy with it.. just to tidy up the wiring now.


My only regret is the spot welding on my battery is not tidy and I do worry it's unsafe in the long run. Could anyone recommend a spot welding machine for someone who isn't going to use it very often.. but that can produce reliable quality welds?


Also for people who have converted Brompton specifically,,
because the spokes are now so short!
they look quite bent like the spoke nipples wont allow them to be at the angle they need to be at, so the spoke itself bends,
has anyone experienced this and found any solutions?

 

[StuartsProjects]

My only regret is the spot welding on my battery is not tidy and I do worry it's unsafe in the long run.

Then clearly if you dont think the battery is safe, you should not use it.

Pictures ?

 

[StuartsProjects]

Also for people who have converted Brompton specifically,,
because the spokes are now so short!
they look quite bent like the spoke nipples wont allow them to be at the angle they need to be at, so the spoke itself bends,
has anyone experienced this and found any solutions?

What question are you actually asking ?

There are a large number of electric Brompton wheels in use around the world.

I have two that I have ridden and they are fine.

I dont understand a need for a 'solution' for the spokes.

 

[saneagle]

Wow... that is so much better!

I didn't expect it to be so powerful.
I put the controller compatible with hall sensor, and an led screen to change the power etc.

Brilliant, thanks for the help, I would not have figured that out without the advice.. when it said hall sensor I always thought it was referring to the pedel sensors.. so as I have a throttle I didn't want that.

Anyway.. very happy with it.. just to tidy up the wiring now.


My only regret is the spot welding on my battery is not tidy and I do worry it's unsafe in the long run. Could anyone recommend a spot welding machine for someone who isn't going to use it very often.. but that can produce reliable quality welds?


Also for people who have converted Brompton specifically,,
because the spokes are now so short!
they look quite bent like the spoke nipples wont allow them to be at the angle they need to be at, so the spoke itself bends,
has anyone experienced this and found any solutions?

The spokes shouldn't be a problem. I've seen many motor wheels like that even on factory ebikes. If you do another conversion, use 14g spokes and a one cross pattern. Avoid rims with eyelets in the holes because the eyelets hold the spokes at the wrong angle, especially if you use 13g spokes.

I had good results with a Sunkko welder, which was about £130. After several years of good service, It has stopped working until I fix it properly. It works when disassembled, but not when I put it back together. There are many stories of them tripping breakers in consumer units because they make spikes in the mains. Maybe I was lucky, but had no problems in two houses. Its welds are very adjustable and predictable once set.

I have since tried a couple of portable welders that run off internal batteries. After some practice, I was able to get some decent welds, but these battery ones are very hit and miss, so you have to do loads of extra welds to be sure. You have to have a delicate touch when you use them. Press too hard and they don't weld. Press too soft and it blows holes in the metal.

I've now got one of these adapted to take the heavier electrodes from a battery one because the electrodes and leads that come with it are too small. I'm full of hope, but I can't try it until I've made up a set of heavy duty leads for the battery. I'll let you know in a week or so how it works.