MSuperX 1300wh 84v - Not charging

[Thomas Perry]

MSuperX not charging.  Charger indicates fine.  Unicycle shows 80v (wasn't fully charged).  Opened up the case and found a part I have not seen on any other MSuperX units or in any teardown videos.  Looking for any assistance in finding a replacement part or advice on whether the part can be removed completely.  Video is below.

If I had to guess, it looks like something to avoid voltages above 84v.  For example, if someone hooked up a 100v charger to the wheel it would halt the charging.  I only have 84v wheels, so this is less of a concern.  The other thought is that it may be a diode, but not sure why unless there were questions on water ingress into the power plug causing a short.

 

[Thomas Perry]

FYI, I found out what this device is...  It is a reverse diode and was only fit on devices by request.  Please keep this thread in case someone else needs to find the device.
 

 

[alcatraz]

You can try to charge the wheel with only one pack. It's a way to figure out which of the two packs is faulty (or the charger if both won't charge individually).

Just remember to never ever reconnect both packs together again unless they have a VERY similar charge. If not you could melt wires.

[Tawpie]

On 6/5/2022 at 12:12 PM, Thomas Perry said:

The other thought is that it may be a diode, but not sure why

My understanding is BG added a blocking diode to the charge port so that the charge port pins aren't "live". Dropping something metal into the charge port shouldn't cause welding anymore. It's almost certainly ok to bypass, but you do lose that safety feature—I'd leave it in there myself.

[RagingGrandpa]

That wheel is from 2018 and it's spotless inside, how is this possible?? 
 

On 6/6/2022 at 6:49 PM, Thomas Perry said:

It is a reverse diode

Right.

It will avoid the charging port pins being "live" - but practically, 84V in a recessed connector like this is not a shock hazard, so it doesn't matter.

And diodes are bad, because there is a constant voltage drop across them, which directly leads to cell imbalance if the charger is not adjusted upwards to match the drop (which none are). And they waste power and get hot while recharging. It's why EUC's stopped using them.

Short-circuit and reverse-connection protection was built-in to all MSX packs AFAIK... you could verify it by carefully connecting a 10A fuse across the charging circuit. With my two 1600wh MSX (including an early-build like yours), the BMS detects overcurrent and turns off before the fuse can melt. 
If the fuse melts during this test, you have no protection- better leave that diode in place, or retrofit your own charging circuit fuse.
Beware that some people purchased "no-battery" MSX's and installed their older MSV3 packs, which had no port protections- so best to prove it yourself.

  

On 6/5/2022 at 3:12 PM, Thomas Perry said:

MSuperX not charging. 

Try removing the diode temporarily, and reconnecting the charger.
I bet it still won't charge past 80V (the diode is likely not the problem).
It means you have imbalanced cells- someone must then unwrap the packs and check individual cell voltages. Don't ride the EUC until this is resolved. 
 

Edited June 23, 2022 by RagingGrandpa

[Tawpie]

5 minutes ago, RagingGrandpa said:

there is a constant voltage drop across them, which directly leads to cell imbalance if the charger is not adjusted upwards to match the drop (which none are)

Super interesting point...