Overvolting Bafang BPM

fourbanger

fourbanger

100 W
Joined
Jul 17, 2014
Messages
214
Location
Vancouver B.C. Canada
Unit says something about 500w (26) or something-or-other about wheel size.

I'd like to push it to about 750w on a 700c wheel. Rear.

Think it will take the heat, or am I pushing my luck a bit?

Thanks, as always.

V.
 
fourbanger said:
Unit says something about 500w (26) or something-or-other about wheel size.

I'd like to push it to about 750w on a 700c wheel. Rear.

Think it will take the heat, or am I pushing my luck a bit?

Thanks, as always.

V.
Click to expand...
Nar, any of those gray market 1000w hub motor kits you see on ebay are really just 500w motors with battery pack and controller that can give 1000w.
For the most part any motor that is rated for 500w must be able to go over 1000w for it to be able to last any distance even past a minimum warranty. Just not good idea to go uphills on 100+f/40+c degree days though.
 
That's kind of the deal right there, 750w cruising on the flat, you are still in 80% efficiency or more.

But take that same 750w, and climb a long enough steep enough hill, and you may spend too much time at 50% efficiency.

This is where a thermometer in the motor can help, you want to spend less time running at that bad of efficiency. You'll see how much faster it heats the motor when you lug it.

Or just using a wattmeter, try to stay out of having the motor use all 750w all the time. When you see watts back off at full throttle, it's because the motor is now turning fast enough to be efficient.
 
There's a number in brackets stamped on the motor. It says something like 36v500W 26(13). The number 13 is the code number for the winding speed. Yours could be anything between 8 and 16. If you post the voltage and code number, we can give some info on what's the best amps and volts to feed it. Depending on the code number it might be better to give more current than volts.
 
It is a (16) indeed. Sorry for the lateness of my reply.

This more or less explains the torquiness of the take off with the weak top end. Coupled with a controller that doesn't want to let more than 12A in.

I'm actually garnering less enthusiasm for this setup by the day. Store bought bike, second hand, battery stolen (off me), and basically just not what I'm interested in.

I might be thinking of selling it, in fact.

Battery's been stolen, and the more I look at it, the more and more it looks like a cop bike...

http://www.eliteelectricbikes.com/index.php/store/velocity-electric-bike.html
 
Get a Code between 13 and 10, and feed it more than 1500 watts. 15s HK lipo is a nice combo at 30 amps or more.

It'll change your view on BPM motors.
 
Interesting, I want to do something similar. Only need to travel under 5km distance, flat and was wondering how much brutality I could beat into a geared motor.

I have a 24Fet 64V controller that has DSP instead of the typical crappy MCU, silky smooth just unsure on what amps.

Soft start throttle for a few seconds with a capped current (so the gears don't get mushed) anyone have idea of what values I should be using?
 
Doubt you'll mush any gears regardless. Haven't heard of anyone doing so for ages.
I use cheapo Ku123 controllers which have a slight ramp that seems to suit well. Just enough to pop the front wheel.
15s 30A is ok if you're not holding hills for too long.

I probably fry a BPM 1 every six months or so, but for the price I toss them, or swap out a clutch assy if that's the issue. It's easy and cheap.

You need to jump the train over to Ballarat (actually Buninyong) soon Tesla and come for a ride. The new pump track in town and surrounding bushland is a haven.

It'd be nice to run some temp sensors against my controller and yours and see how much heat my jaggier signal generates...
 
Interesting, everyone seems to say 25-30A at about 50V

I agree with the disposable nature of the BPM at high power and would prefer to keep changing than use a HT35 (which I honestly think it's a better option)

I think it's all about how you deliver the power band, ramp the current.
Guessing that way I can hit 40A at about 60V

Kepler: Did you have a separate thread for modding the BPM or was it part of the stealth thread?
Sam: I'll take you up on that offer. We can ruin a perfectly good frame while we're at it.

Maybe I need an excuse to head to Suzhou and make a custom wind with beefy silicone wire :mrgreen:

I feel a build thread coming on.
 
It is buried in the Stealth thread about 900 pages back.

I found the sweet spot to be a code 12 on 18S Lipo. for a 24" wheel. On a bigger wheel, code 12 on around 50V to 60V is the go. 25 to 30A current limit and you cant go wrong unless of course you plan to lug up steep hill for an extended period :p :lol:

I started with a code 10. Lasted about 1000km. After going to a code 12, been managing around 2000km out of them. I tend to get over confident with how much power they can handle so the last failures are my own fault. I plan to keep the motor I am using now limited to 1800W. Hopefully I can show some self control :lol:
 
Hehe, fond memories Kepler of us going up that hill in Melb with half @rsed intent to maybe burn ours out. Except I dropped a chain, couldnt pedal, and did indeed cook mine. Stunk the whole car and shed out :oops:

I know that geared hubs have no heat path thru the chassis. And oil cooling gets messy. But I was considering trying to vent mine somehow on the next build, just gotta keep the crap outta the grease somehow.

I really do think they are 90% of a MAC or BMC for a fraction of the cost. No temp sensor though. Maybe that's an option.
 
Kepler, code 12 sounds interesting. Is there a sure fire way to get a code 12 from BMSbattery? Or where would you get one? I have a Bafang BPM code 11 by ordering the Bafang BPM 36v 393rpm.
Kepler said:
I found the sweet spot to be a code 12 on 18S Lipo. for a 24" wheel.
Click to expand...
 
You do need to make sure the vendor is reliable.

Found this old video of Keps while trolling thru youtube. Gold. Hope you dont mind me posting here.


http://www.youtube.com/watch?v=3EgShvl5KvY
 
you cant go wrong, unless of course you plan to lug up steep hill for an extended period
Click to expand...

A couple of years ago, it seems the BPM and MAC upgraded the strength of the plastic in the gears, but the weak link continues to be the poor heat-shedding path. On flat ground (and SHORT hills) it appears they can take quite a pounding from fairly high amps, but on a long and steep uphill...they just get hotter and hotter.

Due to the cheap nature of these mules, I'm surprised there haven't been more experiments on these for air-cooling and liquid cooling. (no-load amps before and after adding ATF, baseline heat, ventilation heat, active cooling heat, etc)
 
I was entertaining some ways to vent the side on my next one without too much dust and sh*t ingress. All that grease.
Aluminium mesh with DP420 to secure it to the side plate perhaps. And a before and after temp range via internal temp sensor ; to "science more harderer."
 
My 36V code 10 get quite noisy right at 25.0mph/330 rpm (speedo cal=2030mm). I replaced the clutch assembly and the problem remains. In all other respects as long it is kept below 25.0 mph it works fine. I'm just wondering if others have had this problem with their BPM's (version 1)?

-R
 
I've had a bad hall connection in the past, there's a mid-throttle resonant frequency that sounds like a F1 car under your butt.
Redid all my hall plugs and it went away.
 
I forgot to say I am running it sensorless. It made the same noise when I ran it sensored but for whatever reason I found a hall was dead after I changed out the clutch assembly so I switched to sensorless.

-R
 
If it's with a KU controller at more than about 36 volts I've never been able to run them sensorless without a weird harmonic sound in the mid band. Which is surprising as a KU controller will pretty much run anything sensorless...

The other thing to check is the outboard bearings in the case sides. They can really warble.
 
Samd said:
If it's with a KU controller at more than about 36 volts I've never been able to run them sensorless without a weird harmonic sound in the mid band. Which is surprising as a KU controller will pretty much run anything sensorless...

The other thing to check is the outboard bearings in the case sides. They can really warble.
Click to expand...

Yeah, it's a 36V KU93 (older version) running sensorless on a 13S Li-ion battery. I've run smaller geared motors sensorless much faster with no problems. When the halls were working I ran it sensored on the same KU93 and with an early version Infineon 6-FET 4110 controller and got the same sound. I wonder though if the failed hall sensor was marginal at that time. I am planning to order an S09P sensorless controller from BMSBattery in the future for another bike and will try it on the BPM to see if there's any change.

I didn't check the bearings when I had it apart but I will next time I open it up. For right now it's not that big of deal since I don't routinely ride the bike that fast.

-R
 
Yep, a q100 sensorless is my daily bread. But the BPM won't take it.
 
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