Flummoxed by current capacity issue

[TheBikeMan]

I know I'm not an electrical wizard but I thought I knew enough for this not to have me flummoxed the way that it does.
The details:
E-Bike about 5 years old with a brushless motor and hall sensors stopped working. When you turn the bike on and hit the throttle it would sort of run for about a second then clunk clunk nothing.
The first thing I did was check the wires to the motor. I unplugged the bullet connectors and found corrosion. So cut off the bullet connectors and as a test I grabbed some alligator clips that are in very, very thin wire and ran them from the 3 wires from the controller to the 3 wires to the motor. Presto, worked like a champ, except of course the wires were so thin they got hot after a few seconds.
So I figure the problem is solved. I put new bullet connectors on and Blah, the original problem returned. Okay, remove the connectors and connect with the alligators again. Zoom. no problem except they can't take the heat of course. So I soldered the wires together and...the original problem returned.Cut them apart and put the little alligaotors back on and zoom, plenty of power.
So, the only way this thing is working is if I use these tiny little wires that don't have the capacity to handle the current inline between the controller and the motor. Any suggestions?

 

[anotherkiwi]

The battery is knackered. Is it 5 years old too?

When you draw current through the thick wires it is too much for the battery to handle. When you draw through the thin wires the battery can keep up with what the motor is drawing.

 

[TheBikeMan]

Hey Anotherkiwi.
It did occur to me that maybe the battery wasn't supplying enough current but I didn't understand the dynamic of how the current was enough once it was chocked through the thin wire. I've got a couple of different battery cell testers but do you know of one that can test the entire battery? Thanks a million!

 

[anotherkiwi]

If the battery is 5 years old I wouldn't waste my time testing. Best way is to borrow another battery which you know is good and see if you have the same problem. If you don't then send the old battery off to be recycled and get a new one.

 

[TheBikeMan]

Thanks!

 

[Nealh]

The thin wires cause a bottle neck and as AK has said can't draw the same continuous amp supply as thick cables.

 

[TheBikeMan]

Thanks Nealh!

 

[TheBikeMan]

Okay, I tried a new battery and got the same result. So now I'm thinking that it may be the current being output by the control unit. What do you guys think?

 

[TheBikeMan]

If the battery is 5 years old I wouldn't waste my time testing. Best way is to borrow another battery which you know is good and see if you have the same problem. If you don't then send the old battery off to be recycled and get a new one.

Okay, I tried a new battery and got the same result. So now I'm thinking that it may be the current being output by the control unit. What do you guys think?

 

[peter.c]

hi have you checked the cables with a meter could be a broken wire?

 

[TheBikeMan]

The wires on this one run all the way from the inside of the control unit to the front wheel with only the plug in the box on the forks. All wires appear to be in good shape and undamaged. I would have to cut in to them at the control unit to measure any breaks but they look perfect.

 

[wheeliepete]

Sounds like you may have damage to the wires between the connector on the forks and the motor. How does the wire look where it goes into the motor?

 

[TheBikeMan]

Sounds like you may have damage to the wires between the connector on the forks and the motor. How does the wire look where it goes into the motor?

They all look really good. There is no sign of any damage at all.

 

[TheBikeMan]

They all look really good. There is no sign of any damage at all.

Oh sorry, going in to the motor it looks a little rough. I was thinking that since the motor works when we choke the current before it gets to that spot that it would not be suspect. Is that a poor assumption on my part?

 

[Nealh]

The usual suspects are a poor motor cable connection from motor to controller, poor phase wire bullets connections or phase wire shorting.
If wires are damaged entering the slotted axle then repair is possible but very difficult.

 

[wheeliepete]

There maybe one broken wire where the ends are still touching, but not connected. The reduced current may pass through the break, but it is not able to carry the full current. A new motor is prob. the easiest solution.

https://www.yosepower.com/en/category/front-48.html

 

[TheBikeMan]

Hi guys, So we found some wire damage inside the axle. It is down inside and when we take the motor apart there is no way to replace those wires. So we ordered a new motor and wheel. The old motor had the typical set up of 3 wires and a 5 wire all sensor hook up. But the new motor has one extra small wire that is white. When we hook the motor up we get nothing at all as opposed to when we were at least getting the old motor to turn with the tiny wire jumpers. 2 questions? Will the 9 wire motor work when we have 8 wires coming from the control unit? If so any suggestions? Second question. shouldn't we be able to measure 36V going to the motor across some combination of the 3 power leads to the motor? Thanks for thinking about it.
Lareu

 

[awol]

the new motor has one extra small wire that is white

I'm sure this is an internal speed sensor wire so if you already have an external speed sensor on your wheel then leave this small white wire disconnected.

 

[Nealh]

White wire is internal speed sensor it is not needed or needing to be connected if you already have ext sensor.

When powered up you should see 11.4v - 14v (dependant on battery state of charge) across each phase when the motor is activated via pas or throttle, you will see 0v with no motor activated.
Measure gnd to phase.
Try motor with out halls connected and brake sensors disconnected.
Other wise carry out a continuity check on the 8 wires from controller to motor connector

 

[Nealh]

When a hub plays up using throttle is a bad idea so pas only, throttle power usually gives max amps so damage can occur to the controller esp the mosfets. These can be damaged so after going through the above to rule out a wire fault you will need to test controller mosfets, if the checks don't marry up then controller is done for.