motor started locking up, vibrating?

I have a fat bike with a MXUS 3000 watt hub motor. It was working well but on my last ride, I ran into a problem.

I live on the top of a pretty big and steep hill (around 10-15% grade) but it's relatively short (maybe 200 meters or so). Most hub motors have trouble going up but my bafang 750w mid-drive bike works well. This bike has a pretty powerful hub motor so it's able to make it up the hill although at the end of the hill it does slow down a little bit. I'm running the mxus 3000 watt motor with a 60 amp sine wave controller and 60v 20ah battery.

On my last ride, I was riding to work so I was going down the steep hill. I have regen turned on so I was going down the hill in regen so the motor was having some periodic grunts and such but seemed normal to me.

At the bottom of the hill, when I accelerated instead of the smooth acceleration that I normally get, it sputtered, vibrated, etc. I seemed to be ok for a second but then would go back to not working, etc. Sometimes the motor would not respond at all to throttle.

I turned back and of course the bike was not able to make it up to the steep hill so I ended up walking the bike up the hill and going back home. On the flats, it would sputter a bit but sort of make it like it's crippled but I walked it most of the time.

Tonight I took a closer look and took all of the wires apart and noticed that the 5 phase wires looked fine on visual inspection. The 3 hall wires (blue, yellow, green) on anderson power pole looked ok but when I tried to pull them apart, the blue and yellow came apart easily as expected but the green was fused together. I cut the wire to get it off to take a closer look and found that the housing had melted. The underlying wire looked ok visually.

I'll try putting on a new anderson tomorrow but do you think that maybe I was just putting too many amps through those andersons? I didn't install this but assuming these are 45 amp connectors and sometimes I take the bike up to around 3000 watts, with a 60v battery that would be 50 amps. I rarely do that though and it's just peak so never sustained but I have sustained it at the 1000-2000 watt level a lot.

Any other thoughts? Bad controller? Thx!

I think you're reversing the terminology. The 5 wires are your halls, and the 3 are your phases.

Andersons have to have floatng contacts/wires. If you are using fat wires in there, or have the wires or andersons all tied down, the contacts cant' float inside the housings, and so they may not mate flat. When that happens there is high resistance and then high currents melt the housings...which makes the problem even worse and causes more heating, until you get a total disconnect when the contacts are no longer touching.

I've had this same problem for exactly taht reason. Eventually I just stopped using connectors at all, and just solder all my hall and phase wires between controller and motor.



If the motor itself was actually hot, too hot to touch, then it's also possible the hall sensors were either temporarily disabled by the heat, or damaged by it. Have also had this happen.




BTW: phase amps can be many times the battery amps...so at 3kw you might have currents in the 100-300a range on the phases themselves, or more. They don't last long, just pulses, rather than constant, but that's still a lot more than those connectors are rated for. Mostly, you won't see problems...but you can.

thanks amberwolf! yeah, i probably got my wire terminology mixed up. the 5 wires seem fine but i'll put in some new connectors for the 3 wires and see if that fixes this at least temporarily.

i'll also look at using some other connectors. i don't want to solder them together because if i get a flat or do some wheel work outside of the bike, i need to disconnect this. maybe some soldered bullet connectors?

RVD said:

maybe some soldered bullet connectors?

Click to expand...

Yes, I'm fond of those 4mm Bullets from RC world for phase power connections. I'm a fan of APP's but not for motor phase power connections.

For Hall sensor wire connections I like Futaba or JR RC servo connectors. 2 of those handle 5-6 wires (some motors have speed or temperature sensors) but the best thing is that they fit through axle hardware - nuts & washers. They don't exactly lock so you might need to lock them with a small tie-wrap and you'll need a $20 crimper for them.

Doesn't seem like Hall signal's your problem here but that's something you may need to contend with later on down the road.

Ykick said:

RVD said:

maybe some soldered bullet connectors?

Click to expand...

Yes, I'm fond of those 4mm Bullets from RC world for phase power connections. I'm a fan of APP's but not for motor phase power connections.

For Hall sensor wire connections I like Futaba or JR RC servo connectors. 2 of those handle 5-6 wires (some motors have speed or temperature sensors) but the best thing is that they fit through axle hardware - nuts & washers. They don't exactly lock so you might need to lock them with a small tie-wrap and you'll need a $20 crimper for them.

Doesn't seem like Hall signal's your problem here but that's something you may need to contend with later on down the road.

Click to expand...

ykick, i think i got started with anderson power poles way back in the day through your videos.

is there any standard on gender for the motor side vs controller side? i'm not sure why but this stuff always annoys me because i almost always get it wrong. female on controller and male on motor?

RVD.

Rule of thumb: The powered side always gets the female so it cannot accidentally short if unplugged and powered.

With Anderson's, there is no male/female. And I agree on the better solutions for high amps.. My Andersons recently left me stranded... They had been deforming very slightly from the heat, in a way not very visible from the outside, and the ever increasing heat from the connection melted thru the phase wire insulation about two inches back from the plugs, leaving me with that same chugging and then dying thing.

I'm on crimped with no plugs right now, which is great for the heat thing, and cheap and quick, but trying to keep my heavy motor and the heavy frame from yanking on each other was a giant pain when I had to replace the tire recently. I was suddenly wishing for bullets.

I had a similar issue with the green wire.

A while ago I had my controller and halls burn out and the green wire, fuse (popped) and hall connector had melted. I replaced the controller, halls and connector but only taped the phase wire up with electrical tape and coincidentally I had the same problem as you today after a couple hundred miles after that repair. My for the initial failure is I overworked a 1000 watt front hub motor on the hills of San Francisco.

Today, I inspected it right after I got to work with another half mile of that vibrating, and the green wire was hot but the controller and wheel were cool. I trimmed the wire past the melted section and was able to ride the problem home (25 miles) with no issues.

I'm no expert, but this coincidence shows there is a reason why the green wire would melt. I inspected the wire and 6 strands of the green wire had broke loose from the spade connector and the color of the wire looked corroded and grey. Never got wet. I attribute this problem to a weak connection.

When assembling a set of andersons, all the contacts have to be lined up nice. If not, the twisted one gets a poor connection and overheats.

So when doing a set of three, like the phases, make sure you line up all three so the contacts agree.

In this case though,, you are running more power than is wise for a set of 45 amps andersons. switch to some big bullets.

i soldered 4mm bullet connectors today and it seems to work well! i suck at soldering but i got it done.

RVD said:

i soldered 4mm bullet connectors today and it seems to work well! i suck at soldering but i got it done.

Click to expand...

Soldering those bullets and similar sized connectors really needs a fat iron tip. Wattage isn't that important, 60-80W is plenty of "temperature".

But what's needed is a large volume of that temperature in order to quickly heat the specific area of the part you're trying to make solder flow on to.

I used to buy Hammerhead tips for my irons but they appear to be hard to find in stock anymore. One alternative is to facricate one from copper electrical parts found at Home Depot or buy a large Chisel soldering tip that fits your iron.

Main thing is don't skimp on getting a good solder flow on 4mm bullets.

good advice! i have one of those pointy tip ones and it was a pain getting the solder to flow.