More E-max Controller Mods - Shunt Resistor Trick

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PJD
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Joined: 11/22/2006
Points: 1411
Finally, a test of new pack and controller mod...

Temperatures are finally well above 0C and the snow is melting. So, for the first time in 7 weeks, I got to use the scooter for my commute and test the new battery pack and amperage upgrade on the older scooter.

With a 1.4 inch, (35mm) added shunt, I am getting 53 amps in economy and 88-90 amps in turbo mode. A bit lower than I was aiming for (95 amps), but good enough.

The new battery pack seems to be working satisfactorily, but at a temperature of about 1C, there seemed to be more qualitatively voltage sag at high amps, as observed on the battery voltage gauge, than with the silicones. No noticeable decrease in performance - in fact top speed seemed to be a bit higher for some reason.

I Will be keeping discharge cycles shallow until the pack is broken in, so there will be no maximum range-per charge report for at least a couple months.

Kmullee
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Joined: 11/17/2006
Points: 34
Re: Finally, a test of new pack and controller mod...

Hey Paul, I’ve been rewiring my new battery pack and in the process I’m replacing all the 8 gauge wire with 6 gauge in case I increase the current on my controller and I noticed that the a wire from the controller to the motor is only 10 gauge. I know I’ll only be running up to 100 amps intermittently and the AWG ratings are fairly conservative but 10 gauge is only rated up to 55 amps so I’m a bit concerned, how’s it holding up on your scooter under heavy use does it get fairly warm?

I’m looking into the possibility of running lower gauge wire to the motor but it’s going to be difficult to connect it through the axle like it is.

Keith
2006 E-Max sport @ 60v
http://keiths-evs.blogspot.com/

__________________

Keith
2006 E-Max sport @ 60v
http://keiths-evs.blogspot.com/

PJD
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Joined: 11/22/2006
Points: 1411
Re: Finally, a test of new pack and controller mod...

I believe that for each revolution of the motor, each motor phase wire is energized (forward or reverse) two-thirds of the time, so on average, so for a given percent-PWM, each motor phase wire carries, two thirds of the current that is going into the controller.

As far as answering questions about th wiring, the question is difficult to answer since both my scooters are "old-style" e-max's, which a different wiring arrangement.

In the old style scooters, 8-gauge power wires from the relays went to a 6-terminal Allen-screwed junction block mounted next to the relays (which aren't enclosed in the box that the new-style scooters used). From the junction block, paired green insulated wires, with red and and black tape to identify the polarity, run to the controller. Paired, blue, green and yellow motor phase wires then run from the controller to the junction block, where they are attached to single blue, green and yellow wires that run to the motor. They look to be something between 8 and 10 gauge, with tinned strands and odd, loose-fitting rubber-like insulation that burns instead of melts.

I've never noticed the 8-gauge wires getting warm to any degree. I've never checked the motor wires. Next hard ride I'll check. I doubt that it is significant.

jetpeach
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Joined: 10/04/2010
Points: 3
Re: More E-max Controller Mods - Shunt Resistor Trick

Hi, I am getting ready to mod my E-moto Metro (I believe its the same controller as that shown here) but it was unclear to me from these descriptions where the actual shunt goes - I attached the image posted earlier with what I believe the shunt to be, could someone verify this?

Shunt_small2.jpg

As for the process, it sounds like I was a shunt with a resistance of about 2.5 milli-ohms and to drill into the pcb and solder it down? Hopefully when I take a look at it it will appear fairly straight forward... Here's to hoping!

Thanks for all the great posts and information everyone!

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Seattle, WA

jetpeach
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Joined: 10/04/2010
Points: 3
Re: More E-max Controller Mods - Shunt Resistor Trick

Well, I went ahead and had some fun modding away. E-moto metro 2007 scooter. Here are my pics.
jumper.jpg

After removing that jumper, I could go faster than 28mpg but was still dying for better acceleration, so followed up with the shunt resistor trick.
hole.jpg
coathanger.jpg

I just took a look back at the length of coathanger shown previously by PJD, and it's quite a bit longer than mine so maybe I've overdone it, but it works and I love the power! With turbo pressed, I really feel great going up hills now...the only question is how long until I burn something up!
Thanks for all the help everyone!
jet

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Seattle, WA

PJD
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Joined: 11/22/2006
Points: 1411
Re: More E-max Controller Mods - Shunt Resistor Trick

Sorry about missing you post.

Yes, your piece of coat hanger is shorter and maybe thicker. But, my two e-maxs are still running fine on 95 amps and 60 volts - almost three times the 2000 watts the motor is supposedly rated for. Assuming you're riding a well "shaken-down" scooter, and with the moderate summer temperatures of the Seattle area, I don't think you will have any problems.

PJD
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Joined: 11/22/2006
Points: 1411
Re: More E-max Controller Mods - Shunt Resistor Trick

Sorry about missing you post.

Yes, your piece of coat hanger is shorter and maybe thicker. But, my two e-maxs are still running fine on 95 amps and 60 volts - almost three times the 2000 watts the motor is supposedly rated for. Assuming you're riding a well "shaken-down" scooter, and with the moderate summer temperatures of the Seattle area, I don't think you will have any problems.

Getting a good solder joint is difficult, even with a 40 watt solderer, on the heavy-gauge connections on that thick board. I use lots of extra flux, and hold heat on the joint for as long as it takes.

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