GEM T3 controller and high voltage debugging

Edit It was all a mistake on my part. TL;DR

I’ve been upgrading a few things on my GEM and ran into a little quirk with the T3 controller.

I’ve been reading over some of the old threads here, I even found the one where Dave came up with the Magic Magnet idea, but the big thing I found is the T3 stinks. I have a stock T3 as well as a R4F modified one since I snagged a R4F blue motor.

I re-arranged my battery setup. I used to run 96v but now I am at 98v. With the R4F T3 I’m getting a code 16 overvoltage error. I can’t recall if I ever ran at 98 volts so I’m not sure if this is a hard stop on the controller or just my general incompetence.

  • I have removed and added Daves voltage spoof with the same results.
  • I have upped #15 in Sentry to 98v. I even put it back to 72.
  • I had it working with Daves spoof once, just a few mts ago. Happy days. I soldered it all back together, shrink wrapped it and cleaned it up. I thought maybe I had it backwards on accident. while testing. Once I was done, I turned it back on and Code 16. Crapsticks.

I’m not entirely sure how to test the voltage spoof to see if I burned it out. I put a meter inline and before and after it and it always registers 98.

A) Am I correct in saying the T3 cannot be set for HV in the controller? Specifically 98v.
B) Did I burn out the voltage spoof somehow? Possibly by wiring it backward?
C) Can I just grab some 1N5404 diodes, wire them in place of the spoof and call it a day or are those different?

The voltage can be measured across spoof. Backwards won’t damage it. It reads <1v drop the wrong way.
Pm me for part numbers, Not worth my trouble making and shipping spoofs, I have a new Tesla pack wanting my attention. :slight_smile:

This is what a $14k battery looks like in a $1.4k truck.

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All good man, you get at it.

T-2 controller cant run higher then 96 volts is it possible that T-3 controllers are the same?

Others have spoofed T3s. I am looking for a T3 owner to try some field weakening.

Once I get her to move again I can fiddle with that. I was playing with Grants Skiing app today so I shoudl be able to get more accurate numbers instead of “seat of the pants”.

I believe getting speed from the T3 is an issue. However voltage alone should get you where you want to be. If not let’s see what it takes.
T3s are the pariah of the Gem controllers.

Oh I know it.
I’m the proud owner of two now.


I was able to get 35-36. I was just hoping to eek up to 40.

Classic way to get more speed is to shunt the field coil. Something the same resistance as the field might be a place to start. Halving the current.
The other way is spoofing controller in hardware. I have a T3 here that I can crack open and send you for testing. Seems simple enough, but if it was, why doesn’t everyone do it.

You know when you do something incredibly stupid and would just rather let it go than talk about it?

I installed Dave spoof a while ago. Has it been two years? It’s a great little gadget and very well thought out and easy to install. His kit requires no cutting or splicing.
For some reason I did some cutting at some point. As one does I soldered and heat shrank everything I changed.
I went to reconfigure my batteries down to 74v from 96v a few months back. I wanted the range and not the speed for a trip I took to NC. I suspect I took out the spoof then. I don’t recall doing it but it makes sense.

Three days ago I put in additional batteries as I bought a few more and wanted to go to 98v. I looked under the hood and thought i had the spoof installed since I saw red heat shrink.

Over the past two days I have been cutting it in and out and trying various options to no avail. Metering it gave me 98v on both sides. Testing it gave me 0.00 on both sides, when one side should not register when it’s installed correctly.

At this point I ordered new parts to fix it and I just wanted to open up his spoof to see his work.

Once all the heat shrink was removed I had a wire soldered to a wire soldered to a wire, soldered to a wire.
At some point when I removed Daves spoof I am willing to bet I threw it away thinking it was trash. I was testing and retesting my personal splice for two days like a dummy thinking it was the spoof.

It’s Miller time.

At least it was an easy fix. :grinning:

I’m wiring in a bypass switch on the voltage spoof in my car this weekend. I’ve yanked it out twice now while stuck on the side of the road in an effort to make it home. With a three position switch it will be easy to bypass and I’m expecting it will act as an extra layer of security if I leave it in the off position.

You can use a momentary start switch, Spoof only affects the voltage to start.

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I am eeking.

Admittedly 39mph is starting to get scary on the streets I run on.

This was on a my T3 with the Ride4Fun rework, Ride4Fun motor and 98v. MagicMagnet.
Now I need to go over @Old_Houseboater s old posts and do some controller tweaks.


I need to get slightly smaller rims and tires. I’m running 15 Honda rims with fat 60 sidewalls. Too much circumference