Panasonic mid drive sudden stops under load.

[Arkz]

Never had this with any motor before. Happens everytime you gun the throttle. Actually being on the bike it's useless. Being very gentle with the throttle it starts to drive but then still does it. Yet with no load it runs perfectly smooth, motor turns smooth. I've checked the pinion and spur. No chips or damage, all meshing just fine. I figured it was the controller so tried the one on my scooter that's for a 36v 350w setup. Minus the bleeuuurp pwm sound it does the exact same abrupt stopping.

Anyone ever experienced this? I'm baffled. Everything checks out, everything moves smoothly yet...
https://youtu.be/LFVtEAOMjTo

 

[nfmisso]

Sounds like the battery's BMS cutting out due to low voltage.

 

[Arkz]

Sounds like the battery's BMS cutting out due to low voltage.

There is no bms.

 

[amberwolf]

Still seems like a battery issue, where voltage is dropping below an LVC. If there is no BMS, then the active LVC is the controller's.

What is the voltage of the pack dropping to when under load, vs no-load?

 

[Arkz]

Tested with an LFP pack that's at about 39V. Barely drops lower than that due to needing hardly any load to cut out. Also tested with a Lipo pack at about 37V, again drop is tiny. Tested with the controller I bought for it and another similar 36V controller. The fact that it does it on both is what gets me. At first I was sure it was the controller. I was pretty shocked to see it do it on a different one too.

 

[amberwolf]

If the voltages never drop below 39v or 37v, and it's a 36v controller, then it shouldn't be the controller LVC cutting out either. Most likely those controller LVCs would be above 30v, but below 33v. The BMS LVCs should be below whatever the controller LVCs are (for packs that have a BMS).

So...if it isn't an apparent LVC issue, how about a connection issue?

If you have a poor connection anywhere, it's got higher resistance, and so less power makes it thru to the system. If it's high enough resistance, it could drop so much power at the connection that whatever is beyond it simply can't function.

Because the power drop is dependent on current flow, then under load it'll be much worse than no load.

It would make more sense for it to be a battery connection, but that should follow either the battery or the controller. Since it doesn't, it's more likely to be a controller-to-motor phase connection problem


If it's not a connection issue, nor a battery or controller issue, then the most likely problem would be something like a clutch, or some other point inside the drive system that would be affected by a load differently than a no-load situation.

 

[Arkz]

Not that either. The connections are good and solid and there is no slipper clutch.

See what I mean how weird it is? I tried connecting the hall sensor but it made no difference. Both controllers support higher speed motors as well as slow hub drives. It just seems like such a weird problem to have. The controllers act like they're getting stuck between phases, it's so very odd.