Help needed diagnosing point of failure in BBSHD Controller

[mp52]

Hi,

Long story short, in my stupidity, I shorted the display pins on my 1000W 52V Luna BBSHD kit when completing the reassembly (working too late...). It sparked and fried the Ground pin on the green male display HiGo connector. I replaced the main loom and the display fires up but displays battery voltage at 0% (34V or so). A direct voltage test of the battery shows it's charged to 54V which is as expected. No error codes appear on the display however (display is an APT 750C).

I've since opened up the controller (no visible signs of damage) and run continuity tests across all wires. I only have basic electronics skills but have compiled results of the tests in a Google sheet you can view here:

https://docs.google.com/spreadsheets/d/1PEr33IpozqLP6BMsR8CdvjRWFWnI-qQkxPYdGrnyJEQ/

I'm getting stable resistance readings on all the battery ground to phase wires and climbing resistance on the positive to phase wires so it looks like the mosfets are OK. I get no continuity between the ground wire on the 4-pin plug in the controller and the battery ground so am assuming the circuit has shorted somewhere in here.

Can any experienced folk confirm my suspicions here and take a guess whether the controller is actually fried if I'm not getting error codes on the display? Is it likely that an SDM on the PCB has failed? If so, I'll order a replacement controller from Luna but I'd also be keen to try and effect a repair on this controller as a hobby project down the line. I'm assuming if its an IC that's probably not possible but a simpler component might be replaceable yes?

Thanks in advance,
Matt

 

[amberwolf]

Both the display and controller may be fried, if they were both connected at the time. Without knowing which wires shorted, my best guess is that a serial data line was hit and fried, either directly or by feeding voltage backwards thru ground and out some other pin.

IF the misconnect was by a rotation of the plugs compared to each other, so the wrong pins went into the wrong sockets, then differnt current paths would occur in each of the two, so it's possible only the display is fried, but given the general lack of protections these devices have against miswiring...couldn't say without trying known good stuff.

If there are separate serial transceivers then you could try replacing those, but if the system uses the MCU pins directly, it's nto really repairable (you'd have to get MCUs with the firmware already on them, and the only source for that is Bafang, or an old cotnroller with some other defect but a good MCU).

Worth chekcing out, if you hae the time and skills (or acquire them).

 

[mp52]

Many thanks for this informative reply. Thankfully the display was out of the equation. The misconnect was me applying dielectric grease straight from the nozzle to the display cable pins and forgetting to switch the battery off before doing so which shorted the ground and (I'm guessing from it's proximity) the RxD signal wire so your theory sounds on the money.

There's limited documentation on the PCB layout of the BBSHD controller out there but from what I've read it sounds like the serial transceivers are on the MCU itself.

In terms of replacement - this link and the follow-on post give an indication of the likely ease of replacement.

Thanks again!