Help! I zip fault starts up on switching on?

[Ginettaman]

I'm new to the forum and I've bought / restored and had running an old i zip trails but it's developed a fault. When I switch it on the motor instantly fires up shooting the bike forward and often blowing the fuse. I've got it in bits and can't find any obvious fault or burning in the controller? After this happens the power goes off but no lights on at the throttle twistgrip. The issue continues even with the pas and throttle wires all disconnected? Have I got a blown controller or could the fault be something else? When I first got it running it had a faulty connection in the throttle but after that it ran ok for a while. The assist is not very good but it starts up after a turn or two of the crank. Can't find anyone selling the old controller which I presume is for a brushed motor? Scooter parts suggest part CT-2435-001 and 24V 35A as mine has both brake cables joined to one set of wires but it's not the same as my controller with side exit cables. Very tight on space too.

 

[Nealh]

Somewhere there is a likely an intermittent wire fault (broken wire/ false contact) causing the issue, disconnect the brake sensors as well to see if the issue continues.

Also open the controller to check all wire solder connections to the pcb.
With the controller open use a meter and continuity check all wiring ( the meter will beep if wire is intact) , trace each connector end point wire and trace back to the pcb. Look/feel along each wire for signs of a broken wire, inside the outer wire sheath it is often possible to feel an irregularity where the break might be.

The PAS might be easy to sort out, if it uses a magnet disc/sensor how many poles does the disc have ?

 

[Ginettaman]

Somewhere there is a likely an intermittent wire fault (broken wire/ false contact) causing the issue, disconnect the brake sensors as well to see if the issue continues.

Also open the controller to check all wire solder connections to the pcb.
With the controller open use a meter and continuity check all wiring ( the meter will beep if wire is intact) , trace each connector end point wire and trace back to the pcb. Look/feel along each wire for signs of a broken wire, inside the outer wire sheath it is often possible to feel an irregularity where the break might be.

The PAS might be easy to sort out, if it uses a magnet disc/sensor how many poles does the disc have ?

Thanks
Still does it with brake connections disconnected. Something in the system should hold off the power when the rocker switch is turned on? Before it made a small jolt but not enough to shoot off? Inside the controller is what looks like a black relay box? Could the switch circuit to the relay be at fault making it have full power at switch on?

 

[Andy-Mat]

I'm new to the forum and I've bought / restored and had running an old i zip trails but it's developed a fault. When I switch it on the motor instantly fires up shooting the bike forward and often blowing the fuse. I've got it in bits and can't find any obvious fault or burning in the controller? After this happens the power goes off but no lights on at the throttle twistgrip. The issue continues even with the pas and throttle wires all disconnected? Have I got a blown controller or could the fault be something else? When I first got it running it had a faulty connection in the throttle but after that it ran ok for a while. The assist is not very good but it starts up after a turn or two of the crank. Can't find anyone selling the old controller which I presume is for a brushed motor? Scooter parts suggest part CT-2435-001 and 24V 35A as mine has both brake cables joined to one set of wires but it's not the same as my controller with side exit cables. Very tight on space too.

It could even be as simple as a shorted MOSFET. Maybe more than one.
Best of luck.
Andy

 

[Nealh]

Mosfets either do or don't work.

 

[Andy-Mat]

Mosfets either do or don't work.

Industry users usually see that they fail shorted.
From a link:-
Usually, a MOSFET will fail short first. ... Often, the gate oxide will be taken into the diffusion, too, causing a short between all three terminals. Only if the short circuit current after this first mode of failure is high enough to blow the bond wires or the entire transistor, there is an open circuit.
Also see here:-

Google Sites: Sign-in

Access Google Sites with a personal Google account or Google Workspace account (for business use).

sites.google.com

I depends also as to how much resistance is still left in the rest of the circuit, which can prevent the MOSFET, from completely blowing up to open circuit....But they generally always short first!
Its usually easy to identify with an Ohmmeter.
Regards
Andy

 

[Ginettaman]

Industry users usually see that they fail shorted.
From a link:-
Usually, a MOSFET will fail short first. ... Often, the gate oxide will be taken into the diffusion, too, causing a short between all three terminals. Only if the short circuit current after this first mode of failure is high enough to blow the bond wires or the entire transistor, there is an open circuit.
Also see here:-

Google Sites: Sign-in

Access Google Sites with a personal Google account or Google Workspace account (for business use).

sites.google.com

I depends also as to how much resistance is still left in the rest of the circuit, which can prevent the MOSFET, from completely blowing up to open circuit....But they generally always short first!
Its usually easy to identify with an Ohmmeter.
Regards
Andy

 

[Ginettaman]

Inside the controller I found a treacle like substance in places on the pub so I cleaned it off but otherwise all looks well. Caps don't look blown. I'm not sure how to test the 4 mosfets? Do they stop the power going to the motor on switch on? I don't know how the controllers work really. I'll take apart again a photograph the pcb unit.

 

[Andy-Mat]

Inside the controller I found a treacle like substance in places on the pub so I cleaned it off but otherwise all looks well. Caps don't look blown. I'm not sure how to test the 4 mosfets? Do they stop the power going to the motor on switch on? I don't know how the controllers work really. I'll take apart again a photograph the pcb unit.

Check that they all have the same type number, and using a multi meter on Ohms, check between each "leg" and compare the results of each one...this is an un-scientific way to work, but with a bit of luck you will find one drastically different. That one is likely to be the problem.
I simply un-solder the MOSFETs and test them free from other components, and re-solder the good ones back in place.
There are websites that sell replacements. If you cannot find an exact replacement, get one that is as close as possible, but "better", more power for example.
Don't confuse the possible manufacturing date code with the device name/number....
I buy from ebay, and I buy enough (really cheap on there!) to replace all at least once! Overkill, but if you get a second problem later on, no waiting for delivery!
Andy
PS. If you are not a DIYer in electronics, ask a friend who knows how to do the job. But controllers are cheap anyway on ebay, but beware of compatibility.....Not all can be easily replaced.....
PPS. You may find these videos helpful:-

"Cogging" is a sign of a broken MOSFET with the bike battery disconnected!
PPPS. For Brushless DC Motors, there are cheap testers for sale on ebay for about 10 UK Pounds:-

 

[danielrlee]

I think Andy is correct. This is a controller for a brushed motor, so a shorted FET would cause full power runaway.

 

[Ginettaman]

Excellent and something completely new to me to try in lockdown! I don't really understand the testing but I have a multimeter to try. I've looked on eBay for a replacement controller but haven't found anything that looks similar so I've no idea which would work? Most seem to be less than 35 amps too? Most have different connections but if anyone knows which will work can anyone recommend examples as a back up? Brushed motor ones seem hard to find now but they seem cheaper? I have soldering gear but I'm certainly not an expert but happy to have a go. As it stands it's scrap sadly.

 

[Ginettaman]

All the testers seem to be for brushless motors?

 

[sjpt]

Excellent and something completely new to me to try in lockdown! I don't really understand the testing but I have a multimeter to try.

Just don't try forcing the probe deep into your throat to ensure a good reading.

 

[danielrlee]

All the testers seem to be for brushless motors?

Yes, they're of limited use with brushed motor systems. A multimeter is all you need. Start by running through the following guide on testing for blown MOSFETS, provided by the excellent Grin Tech (ebikes.ca):

https://www.ebikes.ca/documents/BlownMosfets.pdf

 

[Ginettaman]

My meter is not digital but on continuity testing on the 3 legs of each mosfet with positive in the battery + connection one does beep on all 3 whereas all the others will make a quiet chirp on one leg? Yes I know it's maybe not the correct way to test. One cap has sticky stuff on top. More sticky stuff around the mosfet legs but I cleaned it off the back of the pcb . Can't read the writing on the mosfet very well but can anyone confirm the part spec I may need?

 

[Ginettaman]

I have a thick black and red set of wires going in + - and a thick green and blue wire coming out so presume these are for the dc motor? Testing with probe in red+ I get continuity beep going to the blue wire but only get a quick quiet chirp from the green? Picture shows my meter and wires.

 

[Ginettaman]

Any ideas before I desolder the mosfet and try and search for a replacement?

 

[Andy-Mat]

All the testers seem to be for brushless motors?

Sadly!

 

[Ginettaman]

Iffy MOSFET out but no idea what spec it is or what the numbers mean on it? This one does seem to have continuity between all 3 legs?

 

[Nealh]

ss41 on ebay.