Super low voltage at controller. Did I kill the Pie? **solved**

[Pwd]

So I was doing a friend a favour and replacing a destroyed Anderson connector on his bike. (I've got extra authentic Anderson SB-50 connectors for sale, pm me for details). The plug was destroyed so I tried to check which was the polarity was; anyways I got a decent sized spark and the pie no longer turns on. (GM China had black as positive and red as negative on the power harness from the battery to the controller) On the battery he was using I got 50V output. After opening the Pie and measuring voltage at the red and black wire soldered to the controller I only got a reading of about 0.84 volts! That explains why its not turning on. The black and red wire seem very rigid and the insulation looked a bit dis-colored. Even with the low voltage, when I removed the battery connection; I could tell the capacitors were draining because the voltage eventually dropped 0.84V to 0V. Could it just be the wires that are preventing the controller from turning on. Is it even possible to damage wires like this and cause the drop from 50V to less than 1V?

[Bikemad]

Hyena's Pre-release Magic Pie did actually have the wires coloured incorrectly, but even though the wires were clearly labelled to identify the correct polarity, he wrongly assumed that someone must have made a mistake with the stickers:


He soon discovered that the stickers were actually correct when he tried to connect the battery connector to his 55.5V LiPo pack and melted a pair of contacts inside the connectors:


Paul, as your friends original connector had already failed, I'm wondering whether the battery wires may have shorted out on the sharp metal edges where they both enter the axle? This could cause either the switch contacts to fail, or the BMS short circuit protection to shut off the power.

Did you measure the 50V output while the battery was actually connected and turned on?

Perhaps the 49V drop was actually within the BMS itself rather than across the length of the battery cables?

Did you measure the voltage across the two Anderson connector contacts?

The polarity on the battery connector should be the exact opposite of this one:


So the connector on the battery side should have its exposed pin connected to the negative terminal, and the enclosed socket connected to the positive connection.

The battery wires are are very stiff, and surprisingly thin, but mine regularly coped with 60 Amps and even withstood a maximum current of over 97 Amps with no sign of any discolouration whatsoever:


It will be interesting to find out what exactly is causing the low voltage problem.

Alan
 

[Pwd]

Thanks for the replies...

I definitely accept responsibility for shorting it out; I just always thought that red was positive and black was negative.

Alan:

I measured the 50V at the end of the battery itself (across the two Anderson contacts), and at the end of the harness before it gets plugged into the power connector coming from the motor.

Here is a pic I snapped of the controller (you can see the black and red on the bottom left of the board):


I'm quite certain the BMS is fine since its putting out 50V... actually I just thought of a test; I can try out the battery on my own bike.

EDIT: The battery works fine on my bike.

[Pwd]

Update: I hooked the battery directly up to the joints on the controller board and it powered on. I tried replacing the positive and negative wires but I'm still getting the .85V. Looks like I'll be buying him a new pie; there is no way I'm replacing the controller; I hate soldering onto boards.

[Bikemad]

Now you've confused me, if it powers up when you apply power directly the controller, why are you concerned about even replacing it?

The fault must be somewhere in the wiring harness and not on the controller.

Alan
 

[Morgen 3Eman]

What you are describing is a classic electromechanical connection failure, if I understand your comments.

To be clear, when you connected the battery directly to the controller, the controller functioned properly, correct?  When the normal wiring path is used, the voltage at the controller is .85 VDC.   Is that correct, or do I misunderstand you?

If that is indeed the case, there is a high resistance fault in the primary wiring.  You can determine the location by measuring the voltage drop across each connection and wiring section.  My first guess is that the Anderson connector that plugs into the battery has been badly arc burned.  If you can access the wires coming out of that housing, take a voltage reading there.  If it measures your low voltage reading, then the failure is indeed in that connector.   The battery side may be OK, as it worked in another system, but you should still visually inspect it.

TTFN,
Dennis