BBSHD Motor shuts off while riding

[greenno]

Been having an issue that was identical with my BBSHD unit the last 2 times I rode it. Charges up completely to 58.8v and runs great and then around 54.1v it shuts off and won't restart. Pedal bike home (it is a bike) and check voltage output of battery at charging connector and main motor connector plugs and its 51.07v. Plug into charger and display on charger registers 54.10v. Unplug from charger and check voltage again at the two connectors and it's now 54v. Plug all connectors back in and push button to start and everything comes back up and voltage display says 53.93v and unit works again.
WTF what would shut unit down? Controller or BMS?
Purchased a "New" Bare Bones unit a month ago and rode it 5 miles and then it quit on me so I took it back to Luna and they were going to exchange it but said it was a controller issue and they just replaced the controller with a "New" one and it has worked fine for 80 miles or so.

After unit dies the first time I checked everything and it checked out as described above so I charged it up to 58.8v and go for another ride and it dies right around the same voltage reading as before. LV Cutoff? BMS? Controller? ME?

Help a brother out any ideas I'm open. Thanks

 

[StuRat]

Plug the USB cable in and check your lvc??

 

[mcfizzlestag]

How many AH is your battery? I use a 14s3p (10.5AH) battery from luna, i hit LVC early at around 46-47V after running 20-22A for an extended period, voltage sag isn't that horrible, but its enough to kick out the controller early.

 

[greenno]

Battery AH is 3, yes 31 so I have tons of range. Probably going to replace BMS and see if that works. I had 60 trouble free miles on unit before this issue.

 

[neptronix]

3AH is far too small to deliver the current to move a BBSHD, no matter what cell you have in the pack.
You are probably hitting low voltage cutoff the second you engage PAS or hit the throttle.

I'd bet this battery gets rather hot also. You are wailing on it and it's vastly underspecced for the job.

 

[greenno]

Don't I feel stupid gotta do a spell check before I post. 31ah is the battery I am using not 3. I don't even think they make a 3ah battery, but I digress. My battery is 126 Sanyo cells 18650GA's rated at 3450mh and 10a discharge. Dropped in a new BMS today and plugged in charger. Will go for a ride mañana and see what happens. 3ah really?

 

[neptronix]

There's actually a vendor who sells 6ah mid discharge batteries and says they'll 'work fine on a bafang BBSHD'.
I thought you had something like that. Voltage sag would immediately be bad out of the box at 30A.

31ah of 18650GA's is certainly enough for the current. GL with the new BMS.
If that fails, it would still help to watch the voltage and note how much dip there is.

Because it would be pretty weird if it was your controller doing that.
Although bafang's controllers are not known for quality construction.