Short error

I own a Carrera Vulcan emtb which I have heavily modified, I am being plagued by cutouts. I run a pswpower 48v 13ah battery. My old controller, a brainpower one from eBay would do this at random, it would make a sort of car ignition noise and freeze up when trying to get going, it would show an error then go away on its own and not reappear for weeks.

Now I've changed to a KT 6 MOSFET 500w controller I have a similar issue, but it's more reproducible. Reducing the current seems to almost eliminate it but not entirely. The error goes as follows:

Switch on bike
Pull throttle or pedal on assist 5
Motor cuts out within moments of trying to start
If throttle held in will display error code 6 which means a short circuit

I have removed connectors, replaced phase and battery wires with thicker ones and soldered them direct. Checked all connections inside the battery. One thing I haven't opened yet is the hub itself. The error is predictable, if I put setting C5 current to more than 6 it will start happening, below this current seems alright (16amps). One other thing is if I ease it in and use the bike for a bit things seem to stabilize as it "warms up" and it will happen less. Pswpower claim their battery is 25amps continuous so it should do it, the problems with both controllers did start when I changed to this battery though.

That is everything, hope somebody can help. I have a multimeter here if that's needed, hopefully there's enough clues here to narrow it down a bit. Cheers!

When you go back to the original battery, does it still have the problem?

If not, then it is definitely the new battery, or at least some property of it or it's connections.

Most of the time when reducing current, or throttling up more slowly, prevents the problem, the battery is at fault.

Either the cells are imbalanced and the battery's BMS is shutting down (not likely in your case, as the displays would go blank with no power to them), or the whole battery (or a significant number of cells) are just sagging in voltage so much under load that the system generates errors or fails to do what it's supposed to.

Whether it's because of bad cells or bad assembly, or simply cells that aren't capable of delivering the current the bike is asking for, I don't know.

You can use a voltmeter to measure each cell group (easiest is at the BMS balance wires) while the bike is under various loads, and see what the voltage is when it does get the problems, and what it is when it doesn't. Note down all those voltages here, and someone can give you an idea if the differences are normal or excessive.

The old battery had a lower current limit anyway. What concerns me is the battery is rated 25a continuous and 50a pulse so it should be capable by their specifications. I haven't checked cell groups yet but I can tell you it sags by up to 4 volts when I do get it to run. Is that excessive? Like I say once it is running it works a lot better, even if I come to a stop most of the time it will run no problems once it's "warmed up".

If the battery was tripping on overcurrent, the bike display would lose power and go dark and you would have to cycle power to restart it.

This seems like more of a controller problem. If the motor actually had a short, it wouldn't run and it would be hard to spin by hand. I suppose you could have an intermittent short, but that is not likely to be consistent.

Is there a way to spin the motor by hand? I'm not familiar with that exact model. I guess one possibility is the motor has a partial short, like one turn of a winding. This would cause abnormally high drag when spinning and probably make the motor run hot.

Double check all the motor wires. Check where the wires enter the motor and check the hall sensor wires. Damaged insulation or a loose connection could cause problems.

fechter said:

If the battery was tripping on overcurrent, the bike display would lose power and go dark and you would have to cycle power to restart it.

This seems like more of a controller problem. If the motor actually had a short, it wouldn't run and it would be hard to spin by hand. I suppose you could have an intermittent short, but that is not likely to be consistent.

Is there a way to spin the motor by hand? I'm not familiar with that exact model. I guess one possibility is the motor has a partial short, like one turn of a winding. This would cause abnormally high drag when spinning and probably make the motor run hot.

Double check all the motor wires. Check where the wires enter the motor and check the hall sensor wires. Damaged insulation or a loose connection could cause problems.

Click to expand...

I replaced and soldered the phase and hall wires directly to the controller, no damage visible on the insulation as far as I can tell. Perhaps inside the casing is a different story. Also it was intermittent with the old controller, the higher current could be making it easier for things to arc and cause problems. Everything runs smooth and cool otherwise

anon4 said:

I replaced and soldered the phase and hall wires directly to the controller, no damage visible on the insulation as far as I can tell. Perhaps inside the casing is a different story. Also it was intermittent with the old controller, the higher current could be making it easier for things to arc and cause problems. Everything runs smooth and cool otherwise

Click to expand...

It's really hard to troubleshoot when the problem is intermittent like that. Since you had the same problem with two controllers, it would point to the motor, but I would not rule out two bad controllers or a glitchy battery connection.

fechter said:

anon4 said:

I replaced and soldered the phase and hall wires directly to the controller, no damage visible on the insulation as far as I can tell. Perhaps inside the casing is a different story. Also it was intermittent with the old controller, the higher current could be making it easier for things to arc and cause problems. Everything runs smooth and cool otherwise

Click to expand...

It's really hard to troubleshoot when the problem is intermittent like that. Since you had the same problem with two controllers, it would point to the motor, but I would not rule out two bad controllers or a glitchy battery connection.

Click to expand...

Ok so what can I check next?

anon4 said:

Ok so what can I check next?

Click to expand...

Unplug the controller from the battery. First measure the voltage across the battery wires going to the controller. There may or may not be voltage stored in the caps. If you see more than 1v, the controller is not shorted. If you see zero, then switch the meter to ohms and measure across the battery wires going to the controller (you may be able to do this on the battery holder). Try reversing the probes and measure again.

If the controller is shorted, it will measure near zero in both directions and not change. A good controller should show a slowly changing value that settles on something much greater than zero.

Another test is to try finding a different load you can put on the battery. I have a big resistor, but you could use a 120v incandescent light bulb or a hair dryer. Hook up the bulb to the battery and see if it glows. Measure the battery voltage.

fechter said:

anon4 said:

Ok so what can I check next?

Click to expand...

Unplug the controller from the battery. First measure the voltage across the battery wires going to the controller. There may or may not be voltage stored in the caps. If you see more than 1v, the controller is not shorted. If you see zero, then switch the meter to ohms and measure across the battery wires going to the controller (you may be able to do this on the battery holder). Try reversing the probes and measure again.

If the controller is shorted, it will measure near zero in both directions and not change. A good controller should show a slowly changing value that settles on something much greater than zero.

Another test is to try finding a different load you can put on the battery. I have a big resistor, but you could use a 120v incandescent light bulb or a hair dryer. Hook up the bulb to the battery and see if it glows. Measure the battery voltage.

Click to expand...

Since the wires are soldered directly, as my battery has a switch can I just switch off and take the insulation off the joins and measure there? If it is shorted won't there be visible evidence inside? And if so, is it fixable?

As for battery I don't really have those things to test, anything else I could use or a different test I can do? I do have a hair dryer but fear the Mrs wrath lol

anon4 said:

Since the wires are soldered directly, as my battery has a switch can I just switch off and take the insulation off the joins and measure there? If it is shorted won't there be visible evidence inside? And if so, is it fixable?

As for battery I don't really have those things to test, anything else I could use or a different test I can do? I do have a hair dryer but fear the Mrs wrath lol

Click to expand...

Can you remove the battery? If so, you can measure on the connector pins going to the bike. Otherwise you may need to actually disconnect one of the battery wires. Yes, you can expose just enough of the wire to get your meter probe on there if that is the easiest.

Some BMS units require the load be completely disconnected to reset.

fechter said:

anon4 said:

Since the wires are soldered directly, as my battery has a switch can I just switch off and take the insulation off the joins and measure there? If it is shorted won't there be visible evidence inside? And if so, is it fixable?

As for battery I don't really have those things to test, anything else I could use or a different test I can do? I do have a hair dryer but fear the Mrs wrath lol

Click to expand...

Can you remove the battery? If so, you can measure on the connector pins going to the bike. Otherwise you may need to actually disconnect one of the battery wires. Yes, you can expose just enough of the wire to get your meter probe on there if that is the easiest.

Some BMS units require the load be completely disconnected to reset.

Click to expand...

I thought if the BMS was at fault the display would cut too?

fechter said:

anon4 said:

Ok so what can I check next?

Click to expand...

Unplug the controller from the battery. First measure the voltage across the battery wires going to the controller. There may or may not be voltage stored in the caps. If you see more than 1v, the controller is not shorted. If you see zero, then switch the meter to ohms and measure across the battery wires going to the controller (you may be able to do this on the battery holder). Try reversing the probes and measure again.

If the controller is shorted, it will measure near zero in both directions and not change. A good controller should show a slowly changing value that settles on something much greater than zero.

Another test is to try finding a different load you can put on the battery. I have a big resistor, but you could use a 120v incandescent light bulb or a hair dryer. Hook up the bulb to the battery and see if it glows. Measure the battery voltage.

Click to expand...

Ok controller reads 50.0v and drops slowly if I keep the probes on. I guess this means it's not shorted right? That's a lot of voltage to hold on to but I had just removed the battery. Battery reads 52v at the prongs and the charge port which is normal. Testing at full current at the point of cutoff it only drops to 51.2v so I guess battery isn't at fault. So there must be a short somewhere in the motor, guessing I'm going to have to strip it down?

Not shorted, so that's good.

Maybe try disconnecting the motor phase wires and try giving some throttle. If the motor is shorted, the controller should stay on when the phase wires are disconnected. It may also give some other error because the motor isn't spinning.

One other test is to disconnect the phase wires and measure resistance from the phase wires to the motor axle or other metal part on the motor. There should be no connection. If you see resistance, there is a winding short to the stator.

fechter said:

Not shorted, so that's good.

Maybe try disconnecting the motor phase wires and try giving some throttle. If the motor is shorted, the controller should stay on when the phase wires are disconnected. It may also give some other error because the motor isn't spinning.

One other test is to disconnect the phase wires and measure resistance from the phase wires to the motor axle or other metal part on the motor. There should be no connection. If you see resistance, there is a winding short to the stator.

Click to expand...

According to these tests all is normal, controller gives "e3" as no motor detected. No resistance between motor axle and phase. Measured the resistance between each phase too as seen that done and all bang on 0.7

It seems like a motor problem but still hard to say for sure.

Try spinning the motor while it's disconnected and see if you feel any resistance. You can also try connecting the motor and do the same test in both directions. You should feel some cogging but no real resistance. If there is a short in the motor, there will be a noticeable drag to spinning the motor fast.

fechter said:

It seems like a motor problem but still hard to say for sure.

Try spinning the motor while it's disconnected and see if you feel any resistance. You can also try connecting the motor and do the same test in both directions. You should feel some cogging but no real resistance. If there is a short in the motor, there will be a noticeable drag to spinning the motor fast.

Click to expand...

I tried this already but didn't notice anything. As its intermittent that's probably why the multimeter didn't pick anything up either. Time to buy a cassette tool and strip it down I think

One more piece of information. Before these 2 controllers I did a shunt mod that went bad and shorted out the controller, could this be the cause of the damage?

anon4 said:

One more piece of information. Before these 2 controllers I did a shunt mod that went bad and shorted out the controller, could this be the cause of the damage?

Click to expand...

That is possible but somewhat unlikely. I suppose it may have partially melted some insulation on the wires somewhere. Where the wires pass through the axle is the most likely area for damage.

fechter said:

anon4 said:

One more piece of information. Before these 2 controllers I did a shunt mod that went bad and shorted out the controller, could this be the cause of the damage?

Click to expand...

That is possible but somewhat unlikely. I suppose it may have partially melted some insulation on the wires somewhere. Where the wires pass through the axle is the most likely area for damage.

Click to expand...

I just remember replacing with a new controller and the display showed a motor error. This went away instantly upon use. Several months later I start to get it randomly. Then I upgrade to this KT and it does it with a certain amount of current. It's like something is arcing when enough current is drawn

It could be two wires touching each other and making contact when there is enough current to make them move a little.

It might be hard to find but if you are lucky it will be obvious.

fechter said:

It could be two wires touching each other and making contact when there is enough current to make them move a little.

It might be hard to find but if you are lucky it will be obvious.

Click to expand...

It definitely isn't obvious. It's frustrating as hell

Did you try taking the motor apart? Not sure how hard it is on that model. Some are a major pain, some are real easy.

fechter said:

Did you try taking the motor apart? Not sure how hard it is on that model. Some are a major pain, some are real easy.

Click to expand...

From what I heard from the Halfords guy when I complained of side to side play it's modular. There are 6 screws then it just slides out so quite simple. I just need a cassette tool to access the plate then I'll take a look

Ok now I have checked every connection inside and out and can't find a problem. One of the battery terminals was slightly loose but tightening it did not fix the problem

I'd take apart the motor at this point and carefully inspect all the wiring. Many times the wires fail where they pass through the axle, but this is hard to see. Sometimes you can slide the wires in or out slightly enough to check the entry points. If you had a short between turns on a winding, it would be very difficult to find but you might see a small burn spot.