Possible causes for BBSHD lacking power

[Mnaq]

Hi
A couple of months ago I noticed that my bike with a 52v BBSHD rarely passed 50 km/h, something it normally did everyday at least in one direction going to work. It was like my speed was reduced about 5-7 km/h. So, I thought maybe things needed some lubrication. My rear hub (Shimano Nexus SG-C7000-5D) was due for first service but I didn't expect it to be the cause. The mechanic said it was in good shape. So, I then greased the motor. Opened the BBSHD and greased the stuff around the main shift in accordance with many Youtube videos. I used Mobil Mobilith SHC 100 grease. I did not strip it down to the nylon gear since I had no real strange noises or similar problems. But nothing improved top speed. The front hub is not turning perfectly without friction, I have been running at 50-55 km/h with really crappy not-so-lubricated hubs before so I doubt that is the cause.

So then I started thinking about the battery since it had 2.5 years of quite heavy use (100 % power about 5 miles per day 5 days all year, and 10 miles total) and no smart smart charger so always 100 % charge. But as I was contemplating this I burned the main battery contact (later I managed to fix it) and ordered a UPP Polly 25 Ah Samsung 5000 battery (40A continuous). I was expecting that to lead to a significant rise in both capacity and power/top speed since my previous battery was a noname 30A 21 Ah battery. But nothing improved. Today I installed the Daniel Nilsson firmware and controller software and upped the maximum current to 33A which the controller (and battery) apparently should be able to handle. But I still didn't get any more power and it actually behaved quite strangely. It might be a faulty battery but what could be other causes for decline in power apart from the battery?

 

[amberwolf]

A slow / steady decline in power is usually the battery sagging more and more in voltage under the same load as it ages.

If there is no voltage sag (or no more than there was when new) then it might not be that.


Does the new battery have the same sag as the old one?


The sag doesn't ahve to be inside the battery, either--it can be at any connection/wiring between the cells and the controller board, from a bad connection, etc.

Another cause can be overheating of the motor causing slow degradation of the magnets. This will cause lower torque, but higher speed. Does the motor spin faster under no load than it used to?


Brake rubbing can also cause it; this will cause the wheel to not spin freely when up in the air, unloaded--normally it should spin freely by hand and keep spinning a good while. Rubbing can cause immediate stop of the wheel and even make it hard to spin by hand, even when you can still ride the bike.

 

[docw009]

"But as I was contemplating this I burned the main battery contact (later I managed to fix it"

That statement suggests a poor fix. Frayed wires. Cold solder joint. If these exist, you can have like a half ohm of resistance that shouldn't be there. At 20 A, that's 10 volts.

 

[Mnaq]

That statement suggests a poor fix. Frayed wires. Cold solder joint. If these exist, you can have like a half ohm of resistance that shouldn't be there. At 20 A, that's 10 volts.

What happened there was that there was a poor connection between the battery holder on the bike and the battery. That melted the battery part. But I managed to dig out the cables and solder on a new contact (the spare male coming with the BBSHD) and connect it directly to the XT60 main cable without using the dock. However, I did not notice any big difference in performance after my fix which also should have eliminated the bad connection problem. The battery probably has sagged some since I have noticed a decline in range.

How do you check "spinningen faster without load"? The speedometer? Problem is that I don't have any reference speed and I have changed firmware since and some settings since also.
The new battery sagged faster I think and behaved quite weirdly with current output being only about 10A after some time under load.

 

[fechter]

Does it still indicate full current on the display when you give it full power? Mine maxes out at 30A. One possibility is a problem in the controller, like a shunt resistor going bad.

Does anything get abnormally hot? If you had excessive friction somewhere, something would be getting hot.

 

[Mnaq]

Well. The strange behaviour I experienced with the new battery also appeared with the old one. It wa running at around 28A for perhaps 5 min and then suddenly it dropped to 10A. It had shown short periods resembling easing off the throttle just a little a few times before that. Something similar had happened with the new battery.

After coming back (old battery) the weird thing was the display was showing 100%. I changed the display back to show volts and it showed 56.7 V. I then measured it with a multimeter and got 55.9. During the ride there had not been any significant drastic drop in volts. When the battery was turned off it showed 3.8 V. I measuered the new battery that I hadn't recharged after yesterday's 10 mile ride with trailer and that one only had 53.9 V. And turned off it still showed 21.4 V (!). I thought a battery urned off would show zero or close to.
Didn't think about temperature. During the ride I tried the walking mode that could show temperature according to Daniel's firmware but I could not bring it forward with the 850C.

Have I bricked my controller?

 

[docw009]

Now back to this drop to 10A. Next time it happens, have your display showing voltage. I wonder if you will see it sag suddenly at 10A.

About what the battery shows at the output when its power switch is turned off. You're measuring with a separate meter? That's probably residual voltage across the BMS. You can check by turning on the BBSHD. That will discharge the voltage to zero, If you then measure the battery voltage again, it should stay at zero.

 

[aae34]

During the ride I tried the walking mode that could show temperature according to Daniel's firmware but I could not bring it forward with the 850C.

Have I bricked my controller?

I've had 850c, and i'm pretty sure it did correctly show whatever i wanted in walkmode as the km/h value on display.

I would try reading the controller again to make sure your change for walkmode display actually got written there.

 

[Mnaq]

Now back to this drop to 10A. Next time it happens, have your display showing voltage. I wonder if you will see it sag suddenly at 10A.

About what the battery shows at the output when its power switch is turned off. You're measuring with a separate meter? That's probably residual voltage across the BMS. You can check by turning on the BBSHD. That will discharge the voltage to zero,

When I was riding it showed volts but I don't recall a simultaneous drop in voltage, but I will repeat the experiment and pay closer attention. The new controller software and firmware I use had the max current set to 33 A but the old battery only reached 28.5 max so that is probably battery max output now. The new battery should according to specs sustain up to 40A continuous (probably over estimated). The residual voltage was measured with a separate multimeter with the battery away from the bike.

What interval should a 52V battery optimally work with and what would a full charge have in voltage? After charging the new battery to green on the charger it has 57.4 V. Damn, I should have invested another 250 bucks in a bluetooth battery such as em3ev despite the freight. But the Swedish crown is low so things are expensive to import.

 

[Mnaq]

I did a new test with both the batteries mounted on the bike. Both maxed out at 28.5 A and none of them had a voltage drop after the current dropped to 10A. Quite the opposite actually since the voltage increased when the amps dropped. The voltage drop under full speed load was bigger in the old battery than the new, like down to 49.5 vs 52-53 in the new. When the amps dropped to 10, from there it actually fluctuated between 6 and 20. Sometimes showing more than what the felt power output was. More like a limping home mode of around 15 mph. After changing battery, the problem occurred faster than for the first (the new) battery which indicates there was some issue related to heat. Unfortunately I didn't feel the motor immediately but just after a couple of minutes. By then it was warm but not burning hot. No problem touching it.

I also tested the freewheel of the motor as being able to back pedal without any significant amount of friction. Is that how you test the "brake rubbing" if the wheel itself has a free wheel?

My experiment indicates to me something wrong with the motor more than the batteries. Is it a faulty controller?

 

[fechter]

Yes, it sounds like a controller problem. It's pretty easy to pull the controller side off the motor and take a look. Most of them are potted, so it may be hard to see anything. It would be worth trying to unplug each connector, inspect the pins, and reconnect. A bad connection on a phase wire might do something like you're seeing. The phase wire connectors can get bent and loose sometimes. You can unplug the wire and gently squeeze the connector to make it a little tighter and reconnect.

 

[aae34]

bbshd has two sensor. iirc. not very long ago someone was having issues with default settings, where it's using both.
so you might perhaps want to try the different options(just motor or controller vs. "all") there is for it.

when you're were connected to the bike with the config tool, did you look at the output in the "Event Log"-tab ?
it should print those temperatures there, which might help you choosing the sensor for firmware to use.
could be one of them has issues starting working from below 0c, or something like that.

 

[Mnaq]

bbshd has two sensor. iirc. not very long ago someone was having issues with default settings, where it's using both.
so you might perhaps want to try the different options(just motor or controller vs. "all") there is for it.

when you're were connected to the bike with the config tool, did you look at the output in the "Event Log"-tab ?
it should print those temperatures there, which might help you choosing the sensor for firmware to use.
could be one of them has issues starting working from below 0c, or something like that.

The log seemed okay with no error on startup. What is this "tail log" option that's on that page? One would like to be able to log while riding. Is that what it does? I flashed now with only the motor temp sensor activated to see if that changes anything, but I yet have to try it riding.

 

[fechter]

That might make sense. I seem to recall the controller will reduce power when it senses the temperature is too high.

 

[Mnaq]

A slow / steady decline in power is usually the battery sagging more and more in voltage under the same load as it ages.

If there is no voltage sag (or no more than there was when new) then it might not be that.


Does the new battery have the same sag as the old one?


The sag doesn't ahve to be inside the battery, either--it can be at any connection/wiring between the cells and the controller board, from a bad connection, etc.

Another cause can be overheating of the motor causing slow degradation of the magnets. This will cause lower torque, but higher speed. Does the motor spin faster under no load than it used to?


Brake rubbing can also cause it; this will cause the wheel to not spin freely when up in the air, unloaded--normally it should spin freely by hand and keep spinning a good while. Rubbing can cause immediate stop of the wheel and even make it hard to spin by hand, even when you can still ride the bike.

The chain wheel might not be spinning totally free, but I don't know how free it should be. I recorded a film of how it turns and stops but don't seem to be able to upload it . Since the data cable is plugged in it is a very low power level activated. The motor chainbwheel stops in about a second or slightly more from this quite slow speed. It can be turned by hand but doesn't roll frictionless.

There is also a kind of metallic cogwheel sound, like a roller coaster being pulled up the first hill at the start of a ride, noticeable at low speed. At higher speed it more becomes part of the general noise. Is this sound normal or should the motor rather produce a smoother sound?

If it is brake rubbing or something else, is there anything to be done about it?

 

[aae34]

What is this "tail log" option that's on that page? One would like to be able to log while riding. Is that what it does? I flashed now with only the motor temp sensor activated to see if that changes anything, but I yet have to try it riding.

iirc., tail log is just about direction of log entries in the view. Currently logging while riding requires additional hardware.

edit: removed.

 

[Mnaq]

An update. I disabled the motor temperature sensor using only the controller sensor and after that it worked. Perhaps still a little sluggish compared to "new" but at least I got rid of the problems with the current almost shutting down. I also checked the temperature reading with the walking mode and after 15 min 100% power (27,5 A) it read 65 C. Would this be considered a dangerously high temperature?

 

[fechter]

I wouldn't let it get hotter than that. I try to keep mine under 60C.

 

[aae34]

I go against the default limit w/constant max throttle every time.
No harm done, but i'm on bbs02, while bbshd should definately survive the same.

 

[Mnaq]

Normally I would run for about 7 minutes full throttle, since that is the time it takes to get into "the civilization", just farmland and quite straight boring road in the beginning. After that I run about 35 km/h. This was more a test. I noticed that the temperature rose about 10 C in the last 5 minutes. So I will be a little more careful from now on perhaps.

BTW, can you use the walking mode temperature reading (pressing the minus button on 850C) either rolling at full speed (but no power) or actually on motor power at the same time?