Red thin wire trick volt

[marce002]

Hi

I want to go from 6 to 7 batteries... I have tested and works fine, but if I do a full full charge of the 7set, the "volt sensing" part of the controller does not allow my motor to spin, all rest turn on ok., but motor wont start... if the 7 battery set is almost full, then all will work fine, so I wonder if anyone can help to trick the controller into think that I have 75v permanent, instead of say 90V, and place 90v to the thick red wire.

PROBLEM: "I have tested wiring vol from 6 bats into thin red wire, and 7 bat into thick + , but motor wont start"
SCOOTER sunra hawk 72V (capable of up to 100V though, controller is XRZWK7235A 12 mosfets IRFB3607 ) caps are up to 100v and they are CD288H 40 105 DEGREE TEMP

 

[Chalo]

You could put a series of diodes on the enable wire to drop the voltage into the correct range. I assume there's no significant current on that wire, in which case heat dissipation wouldn't be an issue.

 

[E-HP]

What is the voltage rating of those FETs?

 

[marce002]

You could put a series of diodes on the enable wire to drop the voltage into the correct range. I assume there's no significant current on that wire, in which case heat dissipation wouldn't be an issue.

yes i did similar with a volt divider with 2 res: 10K and 47K and did not work... motor wont spin.... also tried wiring from 20s instead of intended 22s battery and also not spinning (rest is ok).. then back to normal (just in case) and all works fine....

so the thin red wire is not able to sense anything or something trivial i'm missing here (another guy with same bike said he did it)

 

[E-HP]

The thin red wire is only used to turn the controller on. The MCU uses the battery input to sense and set HVC.
What is the rating in those FETs?

 

[marce002]

chalo yes with diodes worked fine, i will collect as many as i need to lower enough... e hp the fets are 75v but they are 12, 4 each phase, full speed wont be used frq only emergency, and Amps will be 35 max