Which BMS controller

[averhamdave]

I'm looking to change the controller on one of my bikes.

On one of my bikes I'm currently running a 36v sensorless controller from ecrazyman that pulls 17a maximum. The motor is an oldish Bafang that is in good order. That set up has been fine for the last 3 years.

For the last 500 miles or so though I have been running with Turnigy lipos, 44.4v nominal (50v actual) with a capacity of 10ah. I have more packs coming and that will go to 15ah.

I am looking to change to a proper 48v controller as I'd like the low volt cut off at 42v but I'd also like the option to revert to hall sensors, a 3 speed selection option via the throttle (which I believes just switches resisitors in the 5v throttle line???) and also a 20a power capability.

I'm looking at BMS as there are other things I'd like from there too. Which controller? The KU93 seems the right one but is only rated at 450w. This suggests a 9a max draw but that can't be right can it?

Does anyone know, will the KU93 deliver 20a under hill climbing type load? If not should I just get one anyway and solder the shunt up? I'm thinking I don't need one of their larger units like the KU151 as I suspect it will be too violent for the application.

Anyone? Thanks

 

[banbury frank]

Hi All you are going to do is tear the motor to bits if you want real power at 48 volts use the



Q11 48V1KW Rear Driving E-Bike Hub Motor

And the KU151 15Mosfets 1000Watts Universal Brushless Hub Motor Controller



The only moving parts are the 2 shaft bearings

Frank

 

[rpurchon]

get a new one from e crazyman with programme cable,you can set it to whatever you like,
i use a 6 fet one running on 15 cells and 22amp no problems.
richard

 

[Deleted member 4366]

The KU93 is 22amps, which might be a bit high for your motor at 48v. The 450w is its rating. It can give 1200w at 48v. You could file a few notches in the shunt to cut it down a bit. Voltage cut-off is 38.5v.

If replacing the controller, I'd get one of the new ones with LCD display so that you can use a PAS with 5 levels. The three speed switches don't do what you want. They have one position with speed limit (12 or 15mph I can't remember), normal operation, and a very slight speed boost. They only work on the throttle, not the PAS. The S09 would be good if you can file the shunt.

You can change the voltage cut-off in any controller by changing a resistor. You have to identify the voltage divider resistors, which is fairly simple. The thin red wire from the battery powers the controller. It goes to the big resistor and then onwards to the voltage regulators. Before it gets to the resistor, it branches off to somewhere where there's two surface mounted resistors and a capacitor with the middle point between the resistors going directly to the microprocessor, so it's like one of those kids games where you have to identify the line that takes the route through a maze, only it's a bit harder because the lines change sides. It's made easier by the fact that the resistors have 4 digits on instead of three, so you can find them easily, and check that they're the right ones by following the tracks back and forward. It's easier than it sounds.
Here's an example in a KU123, where they're in the corner right next to the thin red wire from the battery. In this case there's an additional resistor alreadt there that you can bring in by joining those pads ZX to change the resistance for 36v/48v operation, which is what you want to do. As long as you can find the resistors , I can tell you how and what to change.

 

[averhamdave]

Many thanks all for the replies so far, particularly Dave who has gone to a lot of trouble with his answer and taught me new things about controllers!

I'm glad I posted because I have other options now. With the info about changing low voltage cut outs, I could do this in my existing controller, right? That would be one of the issues solved.

Whilst in pieces I could solder the shunt a little on my existing controller to give it circa a 20 amp capability. That would be second objective met.

In doing this, I could then run the set up for another couple of hundred miles and see how the motor stands up and if it does tear itself apart then I'd know where I was with that and could place one order with BMS for everything - motor and all.

If and when I get the SO9 controller along with his LCD unit for 5 levels of PAS, will I need to run the crank/pedelec sensor? I currently don't run these on any of my bikes, I just twist and go.

Incidentally can someone give me the link to e-crazyman as I have lost it.

Thanks again, Dave.

 

[rpurchon]

KEYWIN EV LABS ecrazyman@gmail.com

 

[averhamdave]

Thanks rpurchon

I fitted the watt meter yesterday and did a 5 mile run over hilly terrain and really gave the battery some stick - more than I would usually. The set up is the one I have dodne good mileage with.

This is the data I pulled off the watt meter at the end of the ride:

Voltage at start 55
Voltage at finish 52
capacity used 2.19ah / 116wh
peak amps pulled - 16.7
peak wattage - 906

 

[averhamdave]

I have soldered the shunt today (too much really), to up the power and run this motor at higher power to see if it breaks up.

I've just done a mile or so up the road and back (private land) with part charged batteries and the watt meter is now showing:

52v
26a peak draw
1343 peak wattage.

I would suggest that if the motor survives that then all will be well.

I'll try and do a 5/10 mile run today tomorrow through the hills and see how hot things are getting - subject to the motor lasting!

 

[Deleted member 4366]

Check that the motor's actually giving more power. There'es normally a point at which you can push in more, but nothing extra comes out - only heat.

I think somethings going to give. My money's on the gears going first.

Fordulike did something similar. I think he soldered the whole shunt on his Cyclamatic. It was OK until he hit a bump under high power IIRC, and he lost a couple of teeth (from the motor of course).

 

[averhamdave]

Hi All you are going to do is tear the motor to bits if you want real power at 48 volts use the



Q11 48V1KW Rear Driving E-Bike Hub Motor

And the KU151 15Mosfets 1000Watts Universal Brushless Hub Motor Controller



The only moving parts are the 2 shaft bearings

Frank

Frank, thanks. Do you have experience with this motor? It gets mixed reviews on ES. Being non geared, does it have the torque to be a good hill climber?

 

[averhamdave]

Check that the motor's actually giving more power. There'es normally a point at which you can push in more, but nothing extra comes out - only heat.

I think somethings going to give. My money's on the gears going first.

Fordulike did something similar. I think he soldered the whole shunt on his Cyclamatic. It was OK until he hit a bump under high power IIRC, and he lost a couple of teeth (from the motor of course).

I suspect you are correct it that some/ much of that extra power is showing as heat rather than torque.

I'm going to pull the controller out tomorrow and remove some of the solder from the shunt. 20 amps will be plenty for the motor if I can manage to judge the shunt mod right.

 

[averhamdave]

Well I desoldered the shunt a little. Now pulling 20a or thereabouts, ie 1000w

Done about 15 miles since and guess what? The motors making horrible noises! Just as the preachers of doo said it would (only joking)

Off to pull it out and strip it now

 

[averhamdave]

Motor stripped and reassembled using some good s/hand gears. Wow, were they stripped. Bike back together and tested.

Will trying and be more gentle with it now until I can get hold of a set of steel gears.

Q: Have heard it said that one steel gear would be enough - minimise the noise increase and be capable of carrying enough load to protect the two nylon gears. Anyone got a view?

 

[Deleted member 4366]

I've never seen steel gears, although I know they exist. In the meantime, 18 amps at 48v or 22 amps at 36v.

 

[averhamdave]

Steel gears for Bafang. I had a link to a sales outlet but have mislaid it for now, doh!

Steel planetary gears for the Bafang SWXH | Electric trike