Upgrading FETs in KT Controller

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hias9   100 W

100 W
Posts: 238
Joined: Jul 11 2018 12:06pm

Upgrading FETs in KT Controller

Post by hias9 » Mar 08 2019 12:48am

I use a 40amp 12FET KT Controller for my slower bike (52V, 2kW). It easily gets hot under repeated acceleration or uphill.
It uses STP110N7F6 MOSFETs. Vds: 68V, Rdsonmax: 6.5mOhm
Datasheet: https://www.st.com/resource/en/datasheet/stp110n7f6.pdf

I plan to upgrade to IPP020N08N5 FETs (Vds: 80V, Rdsonmax: 2.0mOhm)
Datasheet: https://www.mouser.de/datasheet/2/196/I ... 531352.pdf

Can I simply change the MOSFETs or do I need to make further changes to the controller?

flat tire   1 MW

1 MW
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Joined: Feb 26 2014 12:20am

Re: Upgrading FETs in KT Controller

Post by flat tire » Mar 08 2019 2:05am

I didn't look at the datasheets but if the drive levels and pinout are compatible your upraded mosfets should work as-is.

Pegazus   100 mW

100 mW
Posts: 42
Joined: May 18 2019 8:40am

Re: Upgrading FETs in KT Controller

Post by Pegazus » May 23 2019 4:43pm

So does it work ? I'm interested in the same mod.

By the way looking on mouser.de I don't understand how MOSFET with a lower Rds have the same Id :confused:

-dg   1 kW

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Location: Oakland, CA USA

Re: Upgrading FETs in KT Controller

Post by -dg » May 24 2019 6:51am

I looked at the data sheets and did have one concern. The proposed upgrade FETs have more gate capacitance and slower switching time. I'm not an EE and have no idea how sensitive the timing is in the KT controller. I suppose possible issues might be:

- Possible shoot through and let the magic smoke out.
- High rpm operation may be an issue although I think that is more likely limited by the speed of the cpu.
- Higher switching loss if the controller uses high pwm frequencies.

Anyone who knows more about this (ie almost everyone) please step in and clarify.

That said, try it and see. Report how it works.
If simplicity worked, the world would be overrun with insects.

Pegazus   100 mW

100 mW
Posts: 42
Joined: May 18 2019 8:40am

Re: Upgrading FETs in KT Controller

Post by Pegazus » May 24 2019 3:11pm

And this one ?

https://www.mouser.fr/datasheet/2/196/i ... 226960.pdf

Just to evaluate the max potential gain with a MOSFET upgrade without considering the eventual downside effects of the mod what is the rule of the thumb between the max rated current of the MOSFET on the datasheet and the max current rated on the controller ?

Here is the sum up of the MOSFET spec :
- STP110N7F6 N-channel 68 V, 0.0055 Ω typ., 110 A, STripFET™ F6 Power MOSFET in a TO-220 package

And the controller :
- 40amp 12 with FET KT Controller

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