Do 52V packs increase BBSHD Controller Failures?

hyperdrive

1 mW
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May 9, 2018
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I've been commuting with a BBSHD bike using 52V packs for over a year now, putting about 800 km a month on the bike, on average. I'm running the full 30A (1500W peak), but usually average closer to 300-500W while riding. So far I have fried 4 controllers on two different drive units. Three of the failures appeared to be power FET related (just no more drive power), while the last one causes communication errors before the drive stopped working.

What is perplexing me is that the failures have not occurred at times when the motor was particularly hot, and there has been no evidence of water getting inside the controller unit. While I do run the drive at the full 30 amps for a minute or so here and there, I don't think I'm being overly hard on it.

I'm starting to wonder if the voltage rating on the electronic parts might just be too close to the upper limit of the 52V pack (almost 60V), and with transient voltages, the components are seeing voltage stress and failing over time. I think the power FETs are 75V rated, which is a little close for comfort, but does anyone else have experience with this, or have an idea of the voltage rating of the components in the BBSHD controller? I also have a BBS02 that has been running of 52V packs without issue for several years, but it has not seen all that much use. Would a 48V pack likely be more reliable?
 
My guess is that a 48V / 13S pack would work fine, and would make transient voltage spikes have lower peaks. I use a 52V pack, and if charged to the max 4.2V per cell, it should be 58.8V. I am told the capacitors are 63V max.

I only charge to 4.1V per cell (*57V) and I haven't had a problem for about 2 years on the original controller, although I only usually ride on weekends. I have a small chainring to keep the RPMS up, and try to never bog it down...

I fear this may be an example of a successful product, and the manufacturers are now slowly replacing the electronics with cheaper genetic components...although I have no proof of this.

A 48V pack seems like it would be a reasonable precaution.
 
I've been using a BBS02 for about three years @ 52V off road (so, sometimes at fairly high stress when ascending steep trails) with no apparent "damage". The only problem is the display doesn't reflect the pack voltage accurately. This may be resolved with the new"mini" display when it's mounted.
 
spinningmagnets said:
My guess is that a 48V / 13S pack would work fine, and would make transient voltage spikes have lower peaks. I use a 52V pack, and if charged to the max 4.2V per cell, it should be 58.8V. I am told the capacitors are 63V max.

I only charge to 4.1V per cell (*57V) and I haven't had a problem for about 2 years on the original controller, although I only usually ride on weekends. I have a small chainring to keep the RPMS up, and try to never bog it down...

I fear this may be an example of a successful product, and the manufacturers are now slowly replacing the electronics with cheaper genetic components...although I have no proof of this.

A 48V pack seems like it would be a reasonable precaution.

Yes, I believe that the electrolytic capacitors are 63V rated based on what I recall from the controllers I have picked all the potting compound out of. There are probably getting some extra stress with the higher voltage, although their lifetime is typically more dependent on operating temperature and ripple current (electrolyte dries out over time) and they are not highly sensitive to over-voltage. As they get older, the capacitance drops, which I would expect to cause issues after a couple of years as opposed to 5 months or so, but it could be possible. Running 63V parts at 59V is pushing things from my POV. I'm just surprised that I seem to be one of the few people frying controllers all the time with a 52V pack.

Interestingly, my last failure occurred soon after (but not immediately after) I increased my charge voltage from 4.1V/cell to 4.2V/cell for the part of the day where I only having it sitting at 100% for a few hours, so this may have something to do with it. I will now go back down to 4.1V/cell, except occasionally when I need to get a cell balance on my pack.

It is frustrating that they don't over-design these electronic components more since we are talking a few $$ more in component cost, but for off-shore MFGs like Bafang, the cost of parts is high relative to labor costs, so they are more likely to try and save every penny on parts to make a profit. Maybe someone out there is working on a more robust/powerful drop-in controller for the BBSHD.
 
There is a clear benefit to helping the battery pack last many more months/ years if charged to only 4.1V per cell. There is a bigger benefit if charged to only 4.0V per cell. There is no ageing benefit to limiting the charge to anything below 4.0 V.

Due to the sideways "S" shaped discharge curve, you only lose about 1/17th of the packs range by charging to 80%, however, you may need to spec a larger battery to ensure you have enough range if charging to only 80%

Charging to only 4.0V per cell "might" help your current problem, when using the 52V pack that you already have...
 
spinningmagnets said:
There is a clear benefit to helping the battery pack last many more months/ years if charged to only 4.1V per cell. There is a bigger benefit if charged to only 4.0V per cell. There is no ageing benefit to limiting the charge to anything below 4.0 V.

Due to the sideways "S" shaped discharge curve, you only lose about 1/17th of the packs range by charging to 80%, however, you may need to spec a larger battery to ensure you have enough range if charging to only 80%

Charging to only 4.0V per cell "might" help your current problem, when using the 52V pack that you already have...

Thanks, this is good advice. I have been charging to 4.1 V/cell, but recently went back to 4.2V for some of my charges when I only have the pack sitting at full charge for a few hours. I've gone back to no more than 4.1V/cell now and will see what happens. Would like to go down to 4.0, but am running out of range now, unfortunately. If I get a new 52V pack, though, I will probably be able to run it at 4.0V/cell, at least for a while.
 
I would be suspicious that there may be some other problem causing the controller failures, as the BBSHD has been very reliable even at 52v as long as it's not overheated.

There aren't a lot of things I can think of that would cause intermittent failures like this though. One would be a partial short in the motor windings. An intermittent battery connection could possibly do this too but both of these problems would likely cause some other issues that would be noticed like unexpected shutdown or error messages on the display.
 
With respect to my own failed controller, the MLCC failed to the top right of the AMS1117 5V regulator. Shorted and caused a "Communications Fault".
 
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