BBS01 pushing the limits

[aerosock]

hello people,

i'm an owner of a 350w BBS01B, which i have connected to a 52v(14s) battery pack(fooling the 36v lock with a tvs diode as described here), with the controller set to 20a current(max that's allowed on the bbs01 controller)

it's been working fine for the last couple hundred kms, and regarding the heat, after pushing the motor for quite a bit i could still put my hand on the stator casing(measured aroung 50c with an IR thermometer) but im eager to get moar power.

the limiting factor right now is the controller, my first thought was to get a vesc(flipsky 75100 type deal), that would enable me to
1. push more than 20 amps baseline for more torque
2. push even more amps on top of that with field weakening and get higher top rpm
3. a bonus in the form of extreme flexibility of a vesc in terms of settings(as well as maybe fixing the throttle's 1 second input lag lol)

i, however, am worried about these things:
heat. even though im prepared to do all kinds of things to fight it - potting the coils with some thermal compound, increasing the contact area between coils and the outer casing(PC style thermal pads maybe??), adding additional cooling on the casing with heatsinks, i could even(attempt to) rewind the stator if the need be - but i assume there certainly is a limit where i just melt my windings no matter what - and what i want to know, what is the limit?

iron core saturation. i dont have a degree in electrical engineering(or any degree for that matter), so my knowledge in this aspect is very outside of my competence, but it's something that i've been warned to keep an eye on - apparently there's a threshold where adding more amps to a motor is no use since the iron core would be oversaturated with magnetic field. i have no idea how to estimate this number for my specific motor though... and it's an especially big concern for me, since bbs01 has a 30% thinner rotor than it's bbs02 older brother.


does my plan make any sense and is there a point in attempting this, or will i be disapointed and the 52v/20a is already pushing the physical limits of the motor? it would be quite a bummer if i threw away a hundred bucks on a vesc or a couple hundred on a vesc + cooked motor

thanks

p.s. just want to add that im doing this more for the "science" and out of curiosity, i know that just straight up purchasing a bbshd or tsdz16 would be much cheaper, powerful and reliable

 

[aerosock]

so i guess an update, although my plan of action has drastically changed since the initial post

i ordered the 75100 vesc, waiting for it to arrive. and in the meantime i have realized that the whole idea of trying to get more juice out of an objectively tiny stator wound with such thin wire is just dumb, so i decided to uhhh... upgrade that as well. maybe that's a little too ambitious, but we'll.

basically, what i want to do, is to change out the default motor core with another aftermarket motor. after some research i decided to go with a large drone motor - 8318 rotor, 100kv, around 90*40 casing size. those are usually rated for around 50amps(although with the lack of a large prop blowing a tornado on them im not hoping for that much continuously).

i plan to mount it directly at the same spot where the default motor core goes, using a 3dprinted/cnc machined out of alu adapter plate, and a custom shaft for the motor - since those motors are outrunners im planning to reverse the shaft by routing it through the inside bearings to have everything on the same side. basically like this.

after taking apart the motor i started taking measurements and transferring them to a CAD model but quickly ran into a problem - these gears are an effing mystery.
there are 2 gears im working with - the nylon gear and the steel gear(that's machined as part of the rotor shaft on the default motor core, but i will have to get one machined for my custom shaft on the drone motor)
these measure as follows,
nylon - 32 teeth, 53.8mm outer diameter, left handed, 20 degree helical angle, 1.5 module
steel - 9 teeth, 18.0mm outer diameter, right handed, *the same*, *the same*


and these are the measurements of the "caves" for the gears. I have arrived 32.36mm center distance between the gears, and together with the discrepancy of the actual gear size and projected gear size based on the parameters(the steel gear is almost 0,7mm smaller than a 9 tooth 20deg angle 1.5 module is supposed to be) - I suspect the gears have profile shift(or I just suck with calipers). going to look into it more tonight.

if anyone haa any comments on the idea or more precise measurements of the gears that'd be greatly appreciated

 

[aerosock]

another thing i think I should adress is the gearing. even though I bought the lowest kv motor that's commonly produced in this formfactor(getting one with custom winding is 120€+ so I sticked with the used ones, i got mine for under 40€) it's still almost 2x the rpm/v of the default. even with the smallest chainring available for bafangs(32t), I will end up with pretty awkward gearing(no "tank" gears and an unrealistic top speed) and 237rpm on the cranks(I will be running a 14s battery). which I don't really mind since with such a motor pedaling is basically pointless anyways.


I'm also a little worried about the drive train in general. I have a Shimano deore M530 9 speed set right now. Hopefully it won't get discombobulated on the first ride at 3kw. might also swap it out for 8 speed - the derailleur supports 8, and an 8 speed shifter and casette are not expensive + tougher and cheaper chain.

 

[hillslayer@]

Just bolt a hub motor on the rear and use the mid -drive to help on hills , nothing overheats.

 

[aerosock]

Just bolt a hub motor on the rear and use the mid -drive to help on hills , nothing overheats.

thruaxle bicycle and no money for the Grin motor

and as stated, the point isn't just going fast and cool but the DIY project journey

 

[hillslayer@]

Bbshd on 72 volts is a proven solution.

 

[aerosock]

Bbshd on 72 volts is a proven solution.

my guy i appreciate you trying to help but i literally said that #1 i dont want bbshd #2 i build for a 52v battery #3 this isnt about the best bang for the buck but about upgrading the current bbs01 no matter what it takes

 

[brazilianboy]

I'm running bbs01 @3000w 72v
The secret is low gearing and high voltage.

My controller is a generic from AliExpress that pulls up to 45A under heavy acceleration. I should keep in mind always use low gear to start from a stand still and a have a 3 speed switch. I never start from the most powerful mode.

 

[aerosock]

I'm running bbs01 @3000w 72v
The secret is low gearing and high voltage.

My controller is a generic from AliExpress that pulls up to 45A under heavy acceleration. I should keep in mind always use low gear to start from a stand still and a have a 3 speed switch. I never start from the most powerful mode.

wow, thanks incredible, thanks for sharing. but, does the motor not overheat? did you out a thermal probe inside? because mine, even when being very careful with the throttle, is just so increeedibly hot even after 5-10min of 10-15a draw

 

[aerosock]

I guess a lil update on the project. the motor and vesc came in. also made the first prototype of the casing for the new controller, that will bolt on in place of the stock one.

did a couple of mistakes, like the hole for the controller is to small in general, as well as some bad measurements on the casing size - had to press it against the table to screw in the last bolt haha. I also decided to not bother with designing airflow cooling for the controller, I'll just toss it inside the plastic case and see how it does, worst case scenario I'll redesign it later. since I don't think even the new motor would be able to handle more than 30a continously(Chinese spec sheets rate it at something like 50amps here and there, but without the gigantic drone prop and the measures I will have to take in order for it to not die on the first puddle I ride through, not expecting much), controller shouldn't overheat before the motor does.