How To, 50A BBSHD Controller Mod

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sather
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Re: How To, 50A BBSHD Controller Mod

Post by sather » Nov 19, 2016 7:27 am

EM3ev response to the question of what mosfets they provide in the BBSHD:

"We’re not sure what MOSFETS the BBSHD uses, but they are not 3077 MOSFETS. The BBSHD uses a 12fet controller compared to the BBS02’s 9 fet so there are more MOSFETS to share the current.

There is also a difference in programming. The BBSHD has a much lower current at the lower PAS levels - we now use these settings across our BBS range as they seem to work much better than then older settings.

If you have any other questions, please send us an email.

Thanks
Joseph "

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Re: How To, 50A BBSHD Controller Mod

Post by fechter » Nov 19, 2016 12:14 pm

The one I dissected had 75NF75 FETs. These suck compared to 3077s.
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Re: How To, 50A BBSHD Controller Mod

Post by WoodlandHills » Nov 19, 2016 1:18 pm

It sure looks like the unknown team or solo designer of the BBSHD knew what they were doing! Every component is ideally matched to its task with next to no overhead: find a way to boost one part and something else becomes the new bottleneck. Do all of that and the plastic gear melts before you can do any real harm to the core of the motor....... It's sheer engineering genius! And somehow they have been making and selling them in China, the copy-cat engineering center of the world, for years with no competition or imitators. Not even counterfeiters, how do they do that? Finally we have a BBS02 copy with torque sensing PAS, but it's not making much of an impression in the market AFAIK.
Not to hijack the thread, but reading about your struggles just made me aware of how much of a harmoniously designed package the BBSHD is and I wanted to give a shout out to whoever was responsible....

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Re: How To, 50A BBSHD Controller Mod

Post by sather » Nov 19, 2016 4:27 pm

Ebikes4Real
Do you plan on re-potting the controller when you are finished modifying it? If so with what? Do you need to reapply the thermal paste?

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Re: How To, 50A BBSHD Controller Mod

Post by tomjasz » Nov 19, 2016 9:41 pm

fechter wrote:The one I dissected had 75NF75 FETs. These suck compared to 3077s.
While the consensus is they suck, what is the average Joe losing? I'm running two motors with them. Sarcasm unintended, what am I missing?

Thanks,

Tom
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

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Re: How To, 50A BBSHD Controller Mod

Post by WoodlandHills » Nov 20, 2016 3:53 am

That was my point: the Bafang engineers spec'ed each component so well that in normal use you cannot kill them, but try to hot rod it and damn near everything needs to be upgraded. I suspect that time will tell us that while the mechanical engineers that designed the hard parts left a significant amount of power headroom and the electrical engineers who designed the controller did not, in the near future, the plastic gear is going to be the "fuse" in the system.

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Re: How To, 50A BBSHD Controller Mod

Post by robocam » Nov 20, 2016 4:02 am

Have people been blowing Bafang controllers by hotrodding them?
WoodlandHills wrote:... the mechanical engineers that designed the hard parts left a significant amount of power headroom and the electrical engineers who designed the controller did not...

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Re: How To, 50A BBSHD Controller Mod

Post by WoodlandHills » Nov 20, 2016 4:51 am

These are very early days as far as rodding the HD, so I done think many people have been burning up much of anything! We do know that you cannot run over 61v w/o a shutdown using the OEM controller and that 3077 MOSFETs can handle more power than 75nf75s, but not enough to really make a difference (am I correct about this?). The fact that an outfit like Luna found it easier to make their own controller as opposed to tweaking the Bafang part tells you something.....

So far I am in the "had one for months with no problems" camp, but I'm also about to begin my own hot rod BBSHD test program so I have an open mind (I hope). I am leaning towards the Grin Phaserunner, but if anyone came out with a 72v 45a controller that would bolt into the same place as the stock one I would buy two in a heartbeat! (Probably 3!) Will a Phaserunner fit under a gutted BBSHD controller housing? If it was under a cover, would it need its plastic potted housing and if it did not, would it be much smaller and then able to fit?

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Re: How To, 50A BBSHD Controller Mod

Post by Matador » Nov 20, 2016 9:19 am

WoodlandHills wrote:I am leaning towards the Grin Phaserunner, but if anyone came out with a 72v 45a controller that would bolt into the same place as the stock one I would buy two in a heartbeat! (Probably 3!) Will a Phaserunner fit under a gutted BBSHD controller housing? If it was under a cover, would it need its plastic potted housing and if it did not, would it be much smaller and then able to fit?
Same thing for me, If they made a phaserunner to bolt directly on the BBSHD housing, I'd also buy it a heartbeat. And if they can keep the PAS and the Bafang display to work with it I'd buy three at least !!

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Re: How To, 50A BBSHD Controller Mod

Post by drew12345 » Nov 20, 2016 11:55 am

I've been wanting to buy ERT BBSHD phaserunner kit but then I would have all these extra cables. I really love the clean look of the internal controller. It's nice and stealthy.

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Re: How To, 50A BBSHD Controller Mod

Post by sather » Nov 20, 2016 1:06 pm

The reason the BBSHD has been reliable with the P75NF758 mosfets (rated 80 amps)is that it has two temperature sensors that roll back the power to avoid damage to the controller, windings and nylon gear. Also, the BBSHD uses a 12 fet controller compared to the BBS02’s 9 fets

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Re: How To, 50A BBSHD Controller Mod

Post by teslanv » Nov 20, 2016 1:09 pm

fechter wrote:The 3077s will generate way less heat than the 75NF75s. They should survive way more current than the stator could take too. 3077s should handle 60A easily.
Agreed. The IRFB3077 MOSFETs are very robust. When other components are spec'd properly, and the traces are improved, the 3077's can pump out 15A per set of three. With 12, 60A is possible from the MOSFET's themselves. And their voltage limit is actually 75V, which means if you replace the caps with 100V versions, you can reliably run 16S (67.2V Hot) through them, assuming the controller's programming allows it. I use the 3077 MOSFET on our "smaller" controllers for this reason; More Current from a small package.
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fechter
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Re: How To, 50A BBSHD Controller Mod

Post by fechter » Nov 20, 2016 10:37 pm

The voltage is limited to 60V in the software someplace. It seems like it should be possible to reprogram the value, but it's not something you can do with the existing programming cable and app as far as I know.

Somebody needs to hack the software.
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Re: How To, 50A BBSHD Controller Mod

Post by sather » Nov 24, 2016 9:59 am

Assuming you could hack the controller, the caps are 60 volts and would have to be replaced. There may be other circuit board components that are 60 volts rated also.

Also, there are two temperature sensors in the BBSHD motor/controller. If you modify the shunt, the controller will still roll back power when the motor reaches a certain temperature. Maybe that is why Luna puts the extra cooling fins on their 60volt/50amp modified controller.

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Re: How To, 50A BBSHD Controller Mod

Post by E-mil » Nov 30, 2016 7:55 am

Forgive my naivety, but could it be possible that the system shutoff at +60V is controlled by a simple voltage sensor lead?
Would it maybe be possible to cheat this by means of a voltage divider or something similar?

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Re: How To, 50A BBSHD Controller Mod

Post by fechter » Nov 30, 2016 9:01 am

E-mil wrote:Forgive my naivety, but could it be possible that the system shutoff at +60V is controlled by a simple voltage sensor lead?
Would it maybe be possible to cheat this by means of a voltage divider or something similar?
Yes, I'm sure that's possible if you find the right lead. It will likely cause a change in the battery meter as well.
The FETs are stock rated at 75V. The caps are 63V. The internal voltage regulator has a chip that's rated for 80V. All of these limitations need to be watched.
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Re: How To, 50A BBSHD Controller Mod

Post by vk4bxi » Nov 30, 2016 5:27 pm

I'm sure that it has been nailed down somewhere else....please let me have the link......but as far as I know, three phase motor controllers normally use their output devices in groups of 6 so if you want to "beef-up" an output stage you double up and use two devices per output element and thus you have 12 devices required, or 18 devices for three in parallel. Quite where the 9 devices comes from I'm not sure unless it was an interim solution that involved a complicated output stage to reduce losses(making the motor drive more efficient), but found it was simpler to use more or bigger devices ?

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Re: How To, 50A BBSHD Controller Mod

Post by Alan B » Nov 30, 2016 5:53 pm

The dissipation of the six devices in a controller is usually uneven with three having higher dissipation than the other three. So an in-between of 9 devices uses two parallel devices on one side of each phase output, while using only one on the other side.

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Re: How To, 50A BBSHD Controller Mod

Post by vk4bxi » Nov 30, 2016 10:52 pm

Ok......I sort of get that but, I have designed and commissioned a few of these drives at multi megawatt levels. The thing should be symmetrical, I suspect that it will be the built in body diode losses and capacitance to the casing that might be the culprit. even so a 9 off solution sounds like an engineering fudge/kludge fix.

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Re: How To, 50A BBSHD Controller Mod

Post by fechter » Nov 30, 2016 11:06 pm

I have been pretty much baffled by the 9 FET configuration too. In some of the cruder topologies, they are relying on the body diodes to conduct during the off cycle and not turning on the FETs (not synchronous rectification). The body diodes have a pretty high voltage drop, so have to throw off quite a bit of heat even though they are only conducting a fairly short time. Usually they have a single on the high side and a pair on the low side. During PWM, only the high side is switching. The low side only switches during commutation. So I guess this is to spread out the heat dissipation more evenly amongst the FETs.
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Re: How To, 50A BBSHD Controller Mod

Post by Alan B » Dec 01, 2016 1:39 am

I suspect it is a case of "value engineering", and "marketing" for a larger FET claim.

But, 9 and 18 FET controllers do seem to handle more current than their "balanced" counterparts before failing, so it appears to be real.

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Re: How To, 50A BBSHD Controller Mod

Post by vk4bxi » Dec 01, 2016 5:16 am

Ah hah,
Things start to make more sense to me now. When designing cyclo convertors one is always limited by the volts available because the supply transformers are one of the more expensive parts of the design and more volts cost money. Here we are limited by the battery volts as to what speed we can get out of the motor. To get the maximum volts and thus speed/frequency out of a cyclo there is a technique used that keeps two out of the three phases switched hard to either the high or low side of the supply and only controls one phase (PWM) at a time. The result is an extra 15% volts/speed out of the drive. This might be very useful as battery volts decrease. And also would help the controller devices stay cool. But the one working would probably have heating issues with its low side device. And of course it would probably allow a smaller / slower controller CPU since only one PWM is running at a time instead of three.
Yes it might just be.

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Re: How To, 50A BBSHD Controller Mod

Post by cal3thousand » Dec 01, 2016 7:03 pm

tomjasz wrote:
fechter wrote:The one I dissected had 75NF75 FETs. These suck compared to 3077s.
While the consensus is they suck, what is the average Joe losing? I'm running two motors with them. Sarcasm unintended, what am I missing?

Thanks,

Tom
You're missing on efficiency that would lead to better reliability (as the inefficiencies show up as heat). At stock power levels, you're not missing anything. The BBSHD is made well enough to handle all you can throw at it on stock levels. Start demanding more with modified shunts and your 75NF75 FETs may start to feel the burn. The fact that the controller is in the motor housing doesn't help with overall heat build up at the higher power levels either. Lower RDSon means less heat generation at the same power levels.
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Re: How To, 50A BBSHD Controller Mod

Post by Matador » Apr 01, 2017 6:10 pm

sather wrote:Location of shunts: Look at Ebikes4Reals photos above.
On the third photo down the two shunts are two little rectangles located at about 4 O'clock.
On the sixth photo down you will notice that a third shunt has been soldered on top the other two shunts.

The BBSHD has temperature sensors both in the windings and in the controller. The only reason for Bafang to put them there is to limit power when the temperatures get too high. It only seems prudent to wait and see if the stock lower power mosfets can hold the 45 amps before taking the risky and difficult step of replacing all of them.
Could we solder the additionnal shunts in circuit with a switch to enable/desable some of them ?
I mean with the help of switch, we could do : 1) 2.5 mOhm (30A) ; 2) 1.667 mOhms (45A) ; 3) 1.25 mOhms (60A).
Even better if the switch was on the handlebar... Can even put a relay in controller to minimise impact of long wire resistance to handlebar switch (or use fat wire...).

Or we could make a custom wirewound resistor (see many youtube videos) using electromagnet wire or 10 gauge nichrome wire) with wire taps at different places to get different resistor value...

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Re: How To, 50A BBSHD Controller Mod

Post by fechter » Apr 01, 2017 6:39 pm

Matador wrote:
Could we solder the additionnal shunts in circuit with a switch to enable/desable some of them ?
I mean with the help of switch, we could do : 1) 2.5 mOhm (30A) ; 2) 1.667 mOhms (45A) ; 3) 1.25 mOhms (60A).
Even better if the switch was on the handlebar... Can even put a relay in controller to minimise impact of long wire resistance to handlebar switch (or use fat wire...).

Or we could make a custom wirewound resistor (see many youtube videos) using electromagnet wire or 10 gauge nichrome wire) with wire taps at different places to get different resistor value...
It would be hard to make that work because the switch and the wires going to the switch would have enough resistance to be equal to or greater than the shunt resistance. The switch would also need to handle a good percentage of the shunt current (physically large switch).

The voltage on the shunt goes to a LM358 op amp to boost the level before feeding it to the MCU. The way to make it switchable is to switch a small resistor in the op amp circuit to change the gain. The shunt resistors stay fixed. This way the switch can be tiny and the wires can be long. Downside of this is all the parts are tiny little surface mount things and it may be challenging to solder wires to the right spots.
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