Author Topic: GM:Edge - what could cause Error 7?  (Read 6832 times)

Offline Thingamajig

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GM:Edge - what could cause Error 7?
« on: May 14, 2024, 04:09:22 PM »
This issue is likely a result of my unique arrangement with my ebike build, and not likely an issue with GM motors itself - just wanted to clarify that here.

So, let me start by sharing an image of my ebike setup:


So my hub (GM Edge) shares a throttle with a Mid-Drive motor (TSDZ2B, 500w). The mid drive motor supplies power to the throttle - this was a deliberate choice as i've noticed the GM hubs can have issues on their 5v circuit (That powers throttle among other things)

Inside the thottle, the GM:Edge hub motor is connected to the throttles Signal and Ground outputs. The mid Drive is connected to the Positive, Signal and Ground (ie, mid powers the throttle).

In addition, both front and back brake sensors are connected to both the mid-drive and hub motor. This was more just a redundancy measure to ensure plenty of ground points between the mid drive and hub motor - essential to ensure they read the same throttle voltage.


For most part, this arrangement works great, the mid drive provides plenty of lower end grunt to climb hills, with the hub providing assist in that scenario. Then the hub provides great cruising capability at low power draw - as well as brake regeneration. Couldn't be better and it's a fantastic setup that rides great.

However, i've hit a snag.

While throttling, the Hub motor can throw a little fit whereby it abruptly stops drive with almost a "clunk", it's quite jarring and it's almost attempting to forcibly stop the wheel.

When I investigated on a stand, when this "jolt" occurs, error code 7 is momentarily thrown up on the GM Motor LCD screen, it can sometimes do it multiple times in quick succession, then goes away - often for the rest of the ride.

The issue is quite rare, but it makes me wonder the possible cause. My guess is the hub is getting thrown off by the voltage supplied to the throttle by the mid somehow?

Anyway, I appreciate any replies and thoughts shared (thanks in advance to Alan, if he responds!)

Offline Bikemad

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Re: GM:Edge - what could cause Error 7?
« Reply #1 on: May 16, 2024, 11:48:31 PM »

According to the information I have, the Error 7 on the BAC-601 display indicates an "over current" fault, but I have no idea as to why this is happening.

Perhaps something is interfering with the MOSFET triggering and causing both the Hi and Low MOSFETs on a single Phase output to be momentarily energised simultaneously causing an excessively high current flow across the controller's shunt and simultaneously shorting together two Phase windings (which might also explain the sudden clunk and braking effect).

It might be worth temporarily separating the brake wires on the two controllers to see if the fault still occurs.  :-\
If this cures the problem, you may be able to add a diode to each of the controller's brake wires to prevent the brake signal voltage from being transferred from one controller to the other.

Also, if your mid-drive motor has a sensor on the gear-change to momentarily cut the throttle while changing gears, this could possibly be causing problems with the Edge's controller operation.

Unfortunately, I don't know what else to suggest apart from separating the two systems.

Alan