My Bafang rear hub has finally let me down!

Charliefox

Esteemed Pedelecer
Feb 11, 2015
322
87
79
Culloden Moor Inverness
All started off smoothly as I went on my usual forest trails. A slight quiet groaning from the hub which went away.( had this rarely over the past year or so). Carried on a while then noticed no help on the next uphill. Nothing. Battery lights all on. Sometimes a very slight vibration when operating the throttle. Just as well tommorow is a big storm cos I'll be in the garage trying out alternative throttle, checking the wiring and possibly swopping the controller with another. Is there a way to check if the Hall sensors are OK in the hub? I have a multimeter at the ready. I even have a spare front hub, albeit 500W rather than 350W which might tell me which section of the electrics is not working. Wish me luck!
 
D

Deleted member 4366

Guest
More likely, it was a simple connection fault, but, as I keep saying, NEVER TRY TO RUN A MOTOR THAT'S NOT WORKING PROPERLY BECAUSE YOU'LL DAMAGE THE CONTROLLER.

You can test the hall sensors on most bikes as long as you have block type connectors on the controller, not the waterproof sealed ones.

Switch everything on.
Set your voltmeter to 20v or whatever scale to measure 5v.
Find the motor connector at the controller.
While connected, stuff your probes up the back of the connector at the red and black thin wires - you should see approx 5v
Stuff your black probe up the back of the connector to the black wire and the red one to the blue wire. Turn the wheel slowly backwards. You should see 5v going on and off as the wheel turns.
Do the same from the black to the yellow and the blue wire.

Obviously, they won't switch if you have no 5v, and if they do switch, the halls are OK.

You can test the phase connections too.
Set your meter to 20v A/C
Stuff your probes up the back of any pair of the motor phase wires on the controller side. Turn the wheel backwards and you should see some voltage being generated. Repeat for the other two pairs. No voltage generated means that there's an interruption in the connection between the controller and the motor winding. If the motor is difficult to turn, it means that there's a short between one or more phase wires. You should be able to feel some resistance when the motor turns, but not enough to make it difficult to turn by hand. The short can be a blown mosfet in the controller, so not necessarily in the motor or motor cable. If the resistance goes away when you disconnect the motor, the short is in the controller.
 
  • Informative
Reactions: awol

Charliefox

Esteemed Pedelecer
Feb 11, 2015
322
87
79
Culloden Moor Inverness
Found the fault. Your checks worked out well. When you say 20Amp ac and motor phase wires I assumed the thick motor wires. All generated a little voltage but not much. Checked continuity between the motor wires and not all 3 pairs made it. Changed the julet cable from tail of motor (pin side) with a new female side and all wires ok.I know they are connected in star? to avoid several return wires. Rejoined the original cable..it has that ominous bulge from the dodgy connections episode.The bike now worked but cut out later.
Definately the new cable to be plumbed in as soon as my new solder station arrives.