BBS01B - pushing the limits

What kills motors/controllers? Current or power?

I have a BBS01B controller/motor package (not sure what the motor code is). The cadence is a bit slow and I will be fitting a 48V BBS02B controller/battery hopefully within a couple of weeks while using the BBS01B motor. (Yes I could upgrade the whole thing but where's the fun in that?)

I will be doing some experimenting with a temperature probe to check what might be reasonable power to run through (100% keep current, essentially unrestricted max speed) bearing in mind the design intention to fade max power out and thus only use max power for short periods. Currently accessing 250-350W continuous power (7-9A at ~36V) over 10-15 minutes with a few brief pauses seems to do no more than make the outside of the motor/controller casing mildly warm. Typical cadence estimated at 70-80rpm and certainly not below 60 for more than a few seconds at a time.

Hopefully I will establish an answer to the current/power question by monitoring temperatures at a certain current in 36V prior to switching to 48V and then comparing.

Has anyone pushed the BBS01B motor to its limits? If so, what were the limits?

People talk about the windings being different between the BBS02B and 01B motors, to compensate for the higher voltage and keep motor speed and pedal cadence at an appropriate speed. This seems illogical to me since the BBS02B operates approximately 30% (maybe slightly more) faster (surrogate measure of max cadence) than the BBS01B which is in keeping with a 30% boost in voltage (10s to 13s) so why would the windings have been altered? And if they have been altered, why have they been altered upwards - if they think 85rpm is appropriate for BBS01B, why is 115rpm appropriate for BBS02B?

I'm hoping by increasing to 48V but keeping current the same or slightly less I can access more power but with less excess heat generated with lower risk of blowing something.. thoughts?

Sorry for the waffle..

[TLDR]
1. What kills motors/controllers? Current or power? (Secondary question: does heat build up more with increased current and same voltage vs increased voltage and same current?)
2. Has anyone pushed the BBS01B motor to its limits? If so, what were the limits?

Heat is what actually kills motors.

The cause of the heat is, at it's root, the motor being run slow enough under enough load to not have enough BEMF to prevent too much phase current (not the same as battery current) from flowing thru it, and the resistance of the windings and the eddy currents in the stator laminations transforming the part that isn't converted into work (turning the motor) is instead converted into heat.

So, anything that pushes the motor beyond it's limits in the specific situation it is at any moment is what you don't want to do (at least, not for very long). That can be higher current, voltage, or power (which is current x voltage, so increasing either voltage or current increases power, assuming the other is not decreased to match).

If you add temperature sensors in the motor windings and closely monitor those all the time you're pushing the motor, then you can prevent damage.

If you ventilate the motor casing and force-cool it with lots of airflow (pull the air thru, rather than pushing it; works better), then that may also prevent damage, depending on how far you are pushing it.


I haven't read these threads, but they may be of use:
https://endless-sphere.com/forums/viewtopic.php?f=28&t=94022
https://endless-sphere.com/forums/viewtopic.php?f=28&t=92804

amberwolf said:

Heat is what actually kills motors.

The cause of the heat is, at it's root, the motor being run slow enough under enough load to not have enough BEMF to prevent too much phase current (not the same as battery current) from flowing thru it, and the resistance of the windings and the eddy currents in the stator laminations transforming the part that isn't converted into work (turning the motor) is instead converted into heat.

Click to expand...

Great detailed explanation, but probably less of a concern on a mid-drive that won't be lugged like a direct drive hubmotor.

Put simply, voltage kills controllers. The B-revision controllers use IRFB3077 MOSFETs rated at 75V, so 13s even hot off the charger (54.6V) should be fine if there's no software HVC.

Heat from high current burns out and melts motors, but this is easy enough to feel and monitor. You'll never know the limit until you test it under your conditions.

[/quote]

amberwolf said:

Heat is what actually kills motors.

The cause of the heat is, at it's root, the motor being run slow enough under enough load to not have enough BEMF to prevent too much phase current (not the same as battery current) from flowing thru it, and the resistance of the windings and the eddy currents in the stator laminations transforming the part that isn't converted into work (turning the motor) is instead converted into heat.

So, anything that pushes the motor beyond it's limits in the specific situation it is at any moment is what you don't want to do (at least, not for very long). That can be higher current, voltage, or power (which is current x voltage, so increasing either voltage or current increases power, assuming the other is not decreased to match).

If you add temperature sensors in the motor windings and closely monitor those all the time you're pushing the motor, then you can prevent damage.

If you ventilate the motor casing and force-cool it with lots of airflow (pull the air thru, rather than pushing it; works better), then that may also prevent damage, depending on how far you are pushing it.


I haven't read these threads, but they may be of use:
https://endless-sphere.com/forums/viewtopic.php?f=28&t=94022
https://endless-sphere.com/forums/viewtopic.php?f=28&t=92804

Click to expand...

Thanks for the explanation! What I am currently unsure about is whether increasing the voltage shifts the point at which significant energy is wasted at heat (increases the minimum acceptable pedal cadence), or simply extends the top end - i.e. if supplying 250W at 36V at a pedal cadence of 40rpm produces 150W of work and 100W of heat, does supplying 250W at 48V at the same pedal cadence also produce 150W of work/100W heat or would it produce, for example, 100W work/150W heat?

Yes I have read those threads - ta.

fatty said:

Great detailed explanation, but probably less of a concern on a mid-drive that won't be lugged like a direct drive hubmotor.

Put simply, voltage kills controllers. The B-revision controllers use IRFB3077 MOSFETs rated at 75V, so 13s even hot off the charger (54.6V) should be fine if there's no software HVC.

Heat from high current burns out and melts motors, but this is easy enough to feel and monitor. You'll never know the limit until you test it under your conditions.

Click to expand...

Aside from heating the motor and windings so much that the motor burns out, is there anything else likely to go pop in the motor side?
When people break things with these it seems to be either the nylon gear or MOSFETs. As you say, voltage shouldn't be an issue, so once again I presume heat is the enemy for MOSFETs? Based on energy = VIt, it isn't possible to simply say "this 36V controller is rated for 15A and its internals can handle voltages up to 75V so I can put 48V through at 15A", it would instead be necessary to ensure max current would be ~11.5A to produce equivalent heat.
This makes some sense but high voltage cables, for example, are used to transmit power over long distances because losses are less than using low voltage cables with higher current. So I'm a bit confused - what gives? :?

eagercyclist said:

Aside from heating the motor and windings so much that the motor burns out, is there anything else likely to go pop in the motor side?
When people break things with these it seems to be either the nylon gear

Click to expand...

Sure, but such mechanical failures are usually caused by accelerated wear at overload conditions, not catastrophic failure as in the case of the motor burning up. Very different failure modes. If you're overloading, you just have to expect (and accept) such accelerated wear and eventual mechanical failure.

eagercyclist said:

or MOSFETs. As you say, voltage shouldn't be an issue, so once again I presume heat is the enemy for MOSFETs? Based on energy = VIt, it isn't possible to simply say "this 36V controller is rated for 15A and its internals can handle voltages up to 75V so I can put 48V through at 15A", it would instead be necessary to ensure max current would be ~11.5A to produce equivalent heat.

Click to expand...

Not really -- 36V to 48V isn't going to be relevant compared to the higher voltage yielding higher speed and thus exponentially higher drag, which requires more power and thus current, which does cause heat.

fatty said:

Sure, but such mechanical failures are usually caused by accelerated wear at overload conditions, not catastrophic failure as in the case of the motor burning up. Very different failure modes. If you're overloading, you just have to expect (and accept) such accelerated wear and eventual mechanical failure.

Click to expand...

That makes sense.

fatty said:

Not really -- 36V to 48V isn't going to be relevant compared to the higher voltage yielding higher speed and thus exponentially higher drag, which requires more power and thus current, which does cause heat.

Click to expand...

That also makes sense. I notice for my bike at 36V at a maximum speed of ~40kph (based on max gearing and battery state of charge) it is no longer possible (necessary) to sustain power output over 10A on the flat, since I only need approximately 360-400W to maintain this speed.

Yesterday I fitted a 48V battery and BBS02B controller to the 36V motor. Interestingly the cut-off pedal rpm is considerably more than the 30% I was expecting with a 30% rise in voltage - this went from ~85rpm to ~125rpm, i.e. a 45-50% increase in motor rpm. Possibly to do with testing this in a low gear meaning the tail-off in power approaching that limit wasn't apparent, although even in "second" gear the cut off was at 29.5kph; more testing required.

Temperature assessment on the BBS01B controller was incomplete as my 15 minute commute was not sufficient to reach a plateau, but I hope to be able to make some limited comparison with the same power at 48V.

I have much more to do to fully optimise my ride yet, not just programming tweaking but also perhaps changing crank length (already reduced to 150mm). I already removed superfluous sprockets from the 10-speed 11-32T so now I have a 6-speed (keeping gears 1,3,6,8,9,10)..

Hi Cyclist,
Nice read ! Interesting expectations, and results from your limits test.

FYI:
I've applied my "instrumentation" a 'fish tank' ( thermistor ) and digital display to my BBS02B @ 52V
"Raspberry Pi" extruded aluminum heat sink FINS provide effective heat rejection as measured by my instrumentation.
The motor system temperature reaches some plateau well under my BBSO2B factory installed overtemp and shutoff limit.
Mike

Stealth_Chopper said:

Hi Cyclist,
Nice read ! Interesting expectations, and results from your limits test.

FYI:
I've applied my "instrumentation" a 'fish tank' ( thermistor ) and digital display to my BBS02B @ 52V
"Raspberry Pi" extruded aluminum heat sink FINS provide effective heat rejection as measured by my instrumentation.
The motor system temperature reaches some plateau well under my BBSO2B factory installed overtemp and shutoff limit.
Mike

Click to expand...

Excellent! What current are you running (including keep current), and what temperatures are you reaching?
I had thought briefly about adding a heat sink but thought it might attract a bit too much attention. I will keep it in mind!

Although fewer sprockets worked well for the lower voltage BBS01B with its low pedal cadence, I think it is less helpful for the BBS02B and I refitted them today, will see how it goes.

eagercyclist said:

Stealth_Chopper said:

Fins.JPGHi Cyclist,
Nice read ! Interesting expectations, and results from your limits test.

FYI:
I've applied my "instrumentation" a 'fish tank' ( thermistor ) and digital display to my BBS02B @ 52V
"Raspberry Pi" extruded aluminum heat sink FINS provide effective heat rejection as measured by my instrumentation.
The motor system temperature reaches some plateau well under my BBSO2B factory installed overtemp and shutoff limit.
Mike

Click to expand...

Excellent! What current are you running (including keep current), and what temperatures are you reaching?
I had thought briefly about adding a heat sink but thought it might attract a bit too much attention. I will keep it in mind!

Although fewer sprockets worked well for the lower voltage BBS01B with its low pedal cadence, I think it is less helpful for the BBS02B and I refitted them today, will see how it goes.

Click to expand...

52V nominal Luna Wolf MJ1
Temperature ( metal 'skin' surface ) varies with ambient temperature and humidity, air speed across the fins.
I don't keep close track, just noticing the various daily plateaus as I ride.
The system does not shut down due to internal overtemperature.
'Throttle 'only' operation gets the unit warmer,
I believe because the throttle overrides the systems' cadence and power level driven logical functions
With a 44T CR I'm able to use all 9 sprockets over the hilly terrain in rural Eastern CT
Stock, Luna, settings

Stealth_Chopper said:

52V nominal Luna Wolf MJ1
Temperature ( metal 'skin' surface ) varies with ambient temperature and humidity, air speed across the fins.
I don't keep close track, just noticing the various daily plateaus as I ride, & it does not shut down.
'Throttle 'only' operation gets the unit warmer,
I believe because the throttle overrides the systems' cadence and power level driven logical functions
I'm able to use all 9 sprockets over the hilly terrain in rural Eastern CT

Click to expand...

Ah! I presume you are using stock settings and haven't gone into the programming specifics?
Is your temperature probe on the outside?

My FIN reference : Justin Le

https://endless-sphere.com/forums/viewtopic.php?f=2&t=100461

Surface temperature Probe (thermister)
I used 'thermal glue' conductive adhesive and aluminum waterproof tape to secure the probe.
&
5 mm fin height on the controller flat surface may be the most effective heat sinks.
I like the curved pieces with cement fillets to ensure thermal conductivity are working best.

Get a BBS02B. You’ll have 80% fewer headaches. I have BBS01 250w and 350w. Ride within OEM specs and they will serve you well. They need to be kept at high RPM ans efficient use of gears is critical. Wanna be a shifting putz? Buy a BBSHD.

tomjasz said:

Get a BBS02B. You’ll have 80% fewer headaches. I have BBS01 250w and 350w. Ride within OEM specs and they will serve you well. They need to be kept at high RPM ans efficient use of gears is critical. Wanna be a shifting putz? Buy a BBSHD.

Click to expand...

If the BBS01B motor gives up the ghost being used with a BBS02B controller at 48V, I likely will replace with the BBS02B system.
The BBS01B in stock form has plenty of power, my main gripe is the slow cadence - topping out at 75-80rpm is just too slow IMO. Glad you are enjoying yours!

Stealth_Chopper said:

My FIN reference : Justin Le

https://endless-sphere.com/forums/viewtopic.php?f=2&t=100461

Surface temperature Probe (thermister)
I used 'thermal glue' conductive adhesive and aluminum waterproof tape to secure the probe.
&
5 mm fin height on the controller flat surface may be the most effective heat sinks.
I like the curved pieces with cement fillets to ensure thermal conductivity are working best.

Click to expand...

Certainly seems like an effective way to use more power for longer.

I have been running a bbs01 with a 48V controller for around 6 months now.

Mostly been riding in the winter/autumn time here so not much heat to talk about, but now that summer is comming it will be fun to test it in warmer ambient conditions.

I had my motor limited to 16A for most of that period, but I did increase the limit to 20A one month ago, this seems like a better setup for my type of riding.

I am running a 10 speed setup with a 38T in front and 11-42 cassette in rear, alot of hills and I am usually carrying me and bike, 110kg and also a child carrier with two children (60 kg) up and down these hills. No problems pushing the carrier with children our extreme hills in the low gears, not much power needed and motor spinns nice and fine.

As most people before have said, make sure you choose your gearing according to what you will do and there will be no issues.

pomah said:

I have been running a bbs01 with a 48V controller for around 6 months now.

Mostly been riding in the winter/autumn time here so not much heat to talk about, but now that summer is comming it will be fun to test it in warmer ambient conditions.

I had my motor limited to 16A for most of that period, but I did increase the limit to 20A one month ago, this seems like a better setup for my type of riding.

I am running a 10 speed setup with a 38T in front and 11-42 cassette in rear, alot of hills and I am usually carrying me and bike, 110kg and also a child carrier with two children (60 kg) up and down these hills. No problems pushing the carrier with children our extreme hills in the low gears, not much power needed and motor spinns nice and fine.

As most people before have said, make sure you choose your gearing according to what you will do and there will be no issues.

Click to expand...

Thanks pomah.

I am happy with my gearing (46T front, 11-34T 10-sp rear) as I am mostly flat terrain and never even need the 34T to get up anything with good cadence.
I am just about to look at temperature again with increasing current but don't expect there to be an issue, probably even up to 25A, for my riding - as I just don't end up putting down full power for more than a few minutes at a time and the motor/controller don't seem to heat up quickly enough to cause problems, as you would hope, when maintaining cadence.

Does your setup provide that 16 or 20A for significant amounts of time? A lot of people have the keep current set to e.g. 60% which essentially means only 60% of that power is reaching the motor almost all the time.

Thanks for your input!

I reach the 20A when using my low gears going up hills, when I go at max speed down the road I get around 13A or so, so as you say 60% of the max current.

pomah said:

I reach the 20A when using my low gears going up hills, when I go at max speed down the road I get around 13A or so, so as you say 60% of the max current.

Click to expand...

I have my keep current set to 100% because it feels more natural to me not to lose power when I try to put the power down but I am mindful I am therefore running higher actual current than many, even at lower PAS settings. Another reason to keep cadence up!

But just be careful, at higher power usage, the motor will become warmer, there is a limit to how much heat the construction can cool off.

E.g. when riding my previous MAC motor one had to be careful not to use to much power due to the risk of overheating the motor and melting the plastic gears. So most people would stay below 2kW of power. With that said, there is a person here on the forum that has run the mac-motor at 7,2 kW power (I even think that was the nominal power and peak was even higher) with success, but in that case the motor was fitted with a special cooler to be able to maintain the low temperature at the core.

Same thing with this bafang, for everything to be smooth I would keep an eye on the temperature before settling for a final current limit.

pomah said:

But just be careful, at higher power usage, the motor will become warmer, there is a limit to how much heat the construction can cool off.

E.g. when riding my previous MAC motor one had to be careful not to use to much power due to the risk of overheating the motor and melting the plastic gears. So most people would stay below 2kW of power. With that said, there is a person here on the forum that has run the mac-motor at 7,2 kW power (I even think that was the nominal power and peak was even higher) with success, but in that case the motor was fitted with a special cooler to be able to maintain the low temperature at the core.

Same thing with this bafang, for everything to be smooth I would keep an eye on the temperature before settling for a final current limit.

Click to expand...

Today I went for a longer ride involving some hills. I kept temperatures below 43°C (just over 20°C above ambient) which meant keeping power under 600W once it hit 40°C. The most I have put through it is just over 1200W (25A at around 48V) which it tolerates and is pretty rapid.. But you can see the temperature gauge go up and up and it's no good for longer than about 10-20 minutes depending on ambient temperature, and depending on if it's sustained or having brief cooldowns at e.g. traffic lights.

I hope to fit some heatsinks to it in due course which should boost my max long-term (30mins+) continuous power draw. I'll be interested to see by how much.
The BBSHD is the logical upgrade path if it blows up spectacularly, unless Bafang releases something good later this year as rumoured.

I don't think I will push the BBS01B beyond 1200W, it's clear its cooling is inadequate and let's be honest that's hardly a surprise for a motor rated at 250W.

Well my controller died on me...

Max A was set to 15... So I have no idea why or how, but I took it for a 4km run, went away, came back and the display was on, but no support from PAS, no power when I tried the "walk" mode either. Went home, connected a throttle, no feedback

Removed the controller and found that the 63V CAP had swollen. Now I have replaced the controller with my phaserunner and so far so good, my bbs01 is pushing 900W without issue

Can you point me to instructions for wiring in a phaserunner to the BBS01B please?

Mine is running fine with a 44v battery mod but I have some trailer pulling long distance camping plans and 800-1000W could come in handy on some hills.

Hi, sorry for the late reply I did not see you question, please in the future just use the PM feature and I will get back much quicker:

For wiring I used this: https://endless-sphere.com/forums//viewtopic.php?t=91775&start=25#p1360020
(Cant take any credit, not done by me)

For settings regarding phase runner this was the most important ones:
Kp=1 Ki=10 settings in the phaserunner suit

These eliminates the "jerky" behaviour using a throttle or similar.

pomah said:

Well my controller died on me...

Click to expand...

Well now seems there is a problem. Under reporting seems pretty common her. Some poor sap reads this sort of thread not realizing these “fixes” can be expensive lessons. Expect failure and relish the fun. But be prepared for repairs. AND if it’s a pre “B” version it’s really a coin toss.

tomjasz said:

pomah said:

Well my controller died on me...

Click to expand...

Well now seems there is a problem. Under reporting seems pretty common her. Some poor sap reads this sort of thread not realizing these “fixes” can be expensive lessons. Expect failure and relish the fun. But be prepared for repairs. AND if it’s a pre “B” version it’s really a coin toss.

Click to expand...

I agree, I went in knowing there could be a loss for me in it, but I did for the fun of it. Still not sure why it died since I was using "safe" settings, but who knows.

Thanks! I think it's important to post the end results and not lead others to make these changes and not expect to incur the cost of cooking a controller.

You go!