KT error 6 under high current

[anon4]

I've just changed to a KT 500w controller 20a, I had a strange issue with the motor cutting out when going from a standstill, if I kept the throttle held in I would be greeted with error code 6. I switched to voltage display and noticed the battery voltage was collapsing rapidly, suggesting too much current, so I have limited the current a little and all seems well. That said it raises a couple of questions:

Error 6 in the manual means a motor short. Could the BMS cutting the power trigger this code?

My battery is rated 25amps continuous. Can controllers sometimes exceed their rating? Display was showing almost 1000w!?

If it is indeed a motor short, even if only happening at high currents I want to fix the issue. I had this problem before and a hall wire had broken. This time they all appear fine. I have a multimeter, but need guidance on how to test?

 

[vfr400]

There are a lot of things that can cause the current to go too high, most likely is a bad connection. check that the motor plug is in far enough, then check all the motor connections at the controller. Do not try and run the motor with full power when it shows any symptoms of rough running or stuttering, otherwise the current goes too high and you blow the controller.

 

[Nealh]

Phase might be fet issue but usually they either work or not, if using bullets for the phase wires cut them off and solder on an MT60.

Voltage collapse suggests that you battery isn't up to it, limiting the amps still means the battery isn't up to it.

Rather then explain how to test fets use this easy to follow tutorial.
https://www.ebikes.ca/documents/BlownMosfets.pdf

 

[anon4]

Phase might be fet issue but usually they either work or not, if using bullets for the phase wires cut them off and solder on an MT60.

Voltage collapse suggests that you battery isn't up to it, limiting the amps still means the battery isn't up to it.

Rather then explain how to test fets use this easy to follow tutorial.
https://www.ebikes.ca/documents/BlownMosfets.pdf

Its brand new so hopefully not. It does sag pretty hard on startup but it will run fine past that with moderate sag as it accelerates. Could my connectors or wiring just be crap? I extended the motor cable some time ago with thinner wires than it originally had pinched from a wheel that doesn't get used. The connectors do like to get hot I had melting issues when running it in an enclosure

There are a lot of things that can cause the current to go too high, most likely is a bad connection. check that the motor plug is in far enough, then check all the motor connections at the controller. Do not try and run the motor with full power when it shows any symptoms of rough running or stuttering, otherwise the current goes too high and you blow the controller.

Thing is it runs smoothly other than cutting from a standstill, if I ease it in it works fine and is monstrously powerful compared to my last controller

 

[anon4]

Ok I have just realised I cannot reproduce this issue on pedal assist, therefore I am now pretty sure the issue is actually coming from the throttle, doh! Are they repairable at all or is a trip to eBay required?

 

[Nealh]

Hot connectors mean they can't handle the power flowing through them/contact is intermittent or wiring is bottle necking the power flow, either way power isn't freely getting through and is being wasted as heat. Bullets are known for poor transfer and often the plastic insulating burns/melts.

 

[anon4]

Hot connectors mean they can't handle the power flowing through them/contact is intermittent or wiring is bottle necking the power flow, either way power isn't freely getting through and is being wasted as heat. Bullets are known for poor transfer and often the plastic insulating burns/melts.

I am sure it's the throttle now, but I am tackling this issue too. I have removed the extensions I made to the phase wires that were probably too thin for a controller that peaks near 1000w and replaced them with some nice thick ones from an old controller as I think this was generating some of the heat. If the bullets fail again I will change them for something else or just solder them directly to controller

 

[anon4]

Ok the error came back on Pas. I have reduced the current so it doesn't go past 750w on the display and now runs fine. That must be the batterys real limit

 

[Nealh]

Likely battery limitation, my PF cells deliver 858w @36v with 25a controller.

 

[anon4]

Likely battery limitation, my PF cells deliver 858w @36v with 25a controller.

So what's cutting the current, the BMS or the controller? When I get past the startup on full amps I can peak at 980w without it cutting off, it must be trying to pull more than that on startup. Wonder if there is a way to tweak the amps curve so it can use that power without pulling too much at startup

 

[Nealh]

Could well be down to the continuous discharge rate of the BMS of the battery and the cells being used, also the wiring (awg size) battery to controller.
With my PF's (packs in parallel) I see some sag but not voltage collapsing, also I spec my wiring just a little higher to prevent heat/bottlenecking of current also cable run/length plays it's part .
For 800w+ not only do you need good capable cells but also a good bms of 20 - 25a continuous discharge.

 

[anon4]

Could well be down to the continuous discharge rate of the BMS of the battery and the cells being used, also the wiring (awg size) battery to controller.
With my PF's (packs in parallel) I see some sag but not voltage collapsing, also I spec my wiring just a little higher to prevent heat/bottlenecking of current also cable run/length plays it's part .
For 800w+ not only do you need good capable cells but also a good bms of 20 - 25a continuous discharge.

According to pswpower the max continuous is 25a so on paper it should be doing it. The power leads seem thick enough and never get overheated. Maybe 65 Chinese cells just can't do it, thinking about it the sag at it worst was quite big but probably doesn't actually qualify as collapse as it recovered fast and didn't go near the lvc, the same amount of sag can be observed on a cold winters day with enough of a hill. I have emailed pswpower to ask if their KT 20a controllers normally work with this. If they do then I have gremlins somewhere. At least it's running I suppose

 

[Nealh]

The China cells sound like they can't handle the instant demand @20a via.the throttle, with Pas5 the demand isn't instant and takes a few more thou's of a sec to give the full power.

One of my PF batteries is from PSWP and has no issues with power demand @25a demand.

 

[anotherkiwi]

I had a KT controller overheating problem that threw up an error and cut all power. Power came back after it cooled down.

 

[anon4]

The China cells sound like they can't handle the instant demand @20a via.the throttle, with Pas5 the demand isn't instant and takes a few more thou's of a sec to give the full power.

One of my PF batteries is from PSWP and has no issues with power demand @25a demand.

They have replied saying it should handle it. Could too much power to the motor cause this? Officially it's a 250w. Another issue could be the crimp sleeves I extended the power lines with. I might remove them and solder them together

 

[Nealh]

They have replied saying it should handle it. Could too much power to the motor cause this? Officially it's a 250w. Another issue could be the crimp sleeves I extended the power lines with. I might remove them and solder them together

Some 250w hubs are stronger then others so depends on the hub, winding speed etc.
I use 20a @36v on my Bafang cst and am happy with that but no doubt it can take a bit more, though my 29E's don't like it up them.
I also have a 250w Xofo xfv ( I believe it is ) a freewheel hub but not tried that yet, it is same size as Bafang SWXH/K hubs.
Solder directly or use MT60 as I mentioned.

 

[anon4]

Some 250w hubs are stronger then others so depends on the hub, winding speed etc.
I use 20a @36v on my Bafang cst and am happy with that but no doubt it can take a bit more, though my 29E's don't like it up them.
I also have a 250w Xofo xfv ( I believe it is ) a freewheel hub but not tried that yet, it is same size as Bafang SWXH/K hubs.
Solder directly or use MT60 as I mentioned.

These are big hubs, I'm fairly sure it can take the abuse. Changing the power lines will tell

 

[anon4]

Joined the power lines with solder, same result. Hopefully pswpower can shed some light on this issue

 

[vfr400]

Another issue could be the crimp sleeves I extended the power lines with.

Never use crimps on the battery or phase wires.

 

[anon4]

Never use crimps on the battery or phase wires.

Should I just take the bullets off the phase wires and join them direct? Never known this to be a problem before