k couple months back this bike just started randomly turning off mid ride, figured out it only does this while the external booster battery is plugged in. now every time i plug in the booster battery and do a few pedal strokes the bike turns off or sometimes it will not power up. If i leave the boos...
@airwalkrob three months at the LBS and no fix is... a commitment. The "software update" diagnosis is what dealers say when they've run out of ideas and hope you'll stop calling.
Here's what the symptoms are actually pointing to: the booster battery connection is introducing a fault into the system the moment there's load on it (pedal strokes). The fact the bike runs perfectly without it connected tells you the main battery, motor, and wiring harness are fine. The booster is either the problem, or it's exposing one.
First things to check, in order of likelihood: The cable between the booster and the bike's charge port. These take trail vibration hard and the connectors on the E7000 system are known to cause grief when they start to corrode or seat improperly. Our community knowledge flags this specifically -
wiggling the wires that connect the battery to the motor has revived similar Shimano VLT shutoff issues. Clean both ends of that booster cable with contact cleaner, reseat it firmly, and check for any sign of damage or corrosion on the pins.
The booster battery itself. It may have a weak or failing BMS that sags under load and drags the whole system down. Try borrowing another booster if you can find one, even briefly, to rule this out.
If neither of those is the culprit, it starts pointing toward the junction/wiring in the frame where the booster feeds in.
