need help identifying mosfets

andy1956

10 mW
Joined
Jun 24, 2017
Messages
31
Location
UK
It is a controller for a mobility scooter, looks exactly the same as a generic e-bike controller, the mosfets in the controller are blown and have no markings on them. Is it possible to identify the type and rating of the mosfets from the components around them.

60volt battery lithium
80 volt capacitors
35amp controller
here's hoping someone can help with my problem.
 
Are you completely sure they have no markings - sometimes the print is very faint, only shows up with a certain angle of light, and/or hidden by conformal coatings sometimes sprayed on the circuit board (think clear spray paint)... sometimes an alcohol wipe and/or small magnifying glass with a flashlight at different angles will help read the markings.

Otherwise, should be pretty easy to find something comparable or better. (if they are blown, then the 'or better' part would be ideal).

Based on what you mention, looking for at least 80V mosfets and at least 50+amp capacity would be a good start. Try to find the lowest resistance ones you can, then the other major thing would be the form factor are they a standard TO220 or some of the newer flat pack style?

Detailed pics would also help.

You can run a parametric search at several electronics outlets... digikey has always appealed to me.

https://www.digikey.com/en/products/filter/transistors-fets-mosfets-single/278

or as a first guess:
https://www.digikey.com/en/products/filter/transistors-fets-mosfets-single/278-and-gimme-fets-with>80V-and>50A-and<12mohms-RdsON/(but-hopefully-<5mohms)/
 
If you replace all of them, you can choose a different MOSFET that has enough rating. IRFB4110s are possibly overkill for that, but having extra headroom in the ratings won't hurt.

If the existing FETs blew, it may also have blown the gate drivers. After removing the FETs, you can measure resistance from the gate to source connections and see if any look shorted.
 
fetcher makes a good point that I was not especially clear on. If you can't get the part number and get an exact replacement, then replace ALL mosfets the different/new model you choose. Don't have a mix-n-match group of partially old/good ones and new/different model ones. Even then, it might not be a bad thing to replace all of them.

Also, I didn't explicitly state, but once you lock in the form factor and find all mosfets available in that category, you may find you can get even higher voltage/current and lower resistance mosfets for a few cents more. That would certainly not be a bad investment, either.
 
ok thanks for reply's, looks like i will be replacing all the fets with same form factor and higher rating and low resistance cheers
 
Back
Top