Controller upgrade: worth it?

[powersupply]

This in my existing controller that came with the scooter:
http://endless-sphere.com/forums/viewtopic.php?f=2&t=53324#p793681
and everything runs smooth with a 12s configuration. A little too smooth because with 12s4p (12x5Ah LiPos) the voltage drops to 44V and that is indeed slower than the old SLAs (4x12V/20Ah).
So I ordered another of those 5Ah packs (13s4p) to have 48V during general operation. At full charge this would be 54.6V, a little too close to the 60V max of the FETs.
View attachment 1
Being extremely tight on budget (man, all those connectors and etxra stuff add up!) I was thinking to upgrade the 12x 60V FETs with some higher Volt, higher Ampere, lower Ohm (and yes, lower capacity, Miller, avalange. etc) FETs for $20 shipped. Like these:

Was looking to buy some used/new controllers first, but would probably need 12 FET, asked Lyen about his 9 FET but he recommended the 12 FET for my heavy 750W scooter and those are way too expensive for me.

What are your experiences with replacing FETs in controllers aside from the actual work?
Thanks!

 

[DAND214]

How are you getting 13s with just one more pack?

Your controller should be fine, since the original was 48 nominal, Most controllers are so called 48v but that is really mid 52 to 60v. If there are 63 caps then you should have no problem with 13s or even 14s.

changing fets is time consuming, takes some basic but good tools and a good eye. Oh a steady hand helps too.

Dan

 

[powersupply]

4s1p=1s4p after some modding.

As mentioned, the FETs have a breakdown of 60V, that worries me.
Caps are all 75V or higher now.

 

[dnmun]

i would go to 14S lipo. that is what i am focused on with the BMSs i am ordering from bestekpower.com . use a regular 48v lifepo4 charger then also.

 

[powersupply]

That would put me even closer to 60V.
Still contemplating what to do, seems most who upgraded their controllers had no issues.

 

[powersupply]

So I was going to exchange the FETs of my scooter with some higher V and now found this!









Shouldn't the gates of the FETs be decoupled??
I checked the FET (above), it does not have a resistor built in.

The gates on one side are paralleld, the other side just with one resistor.

So how does this work?
Shouldn't this oscillate like hell???

Please enlighten me!