Hiccups on the Zoom Zoom of acceleration

GEM Forum
1

Motor, Controller, Pedal, or connections? 2012 E2 under acceleration will hit a flat spot and not accelerate through it, hesitates, pauses, and then sometimes accelerates to the next speed. Monitoring the BMS current draw it is under 100 amps when it’s pausing. Then it can grab a fat chunk of 100+ amps and zoom to the next speed. I checked motor temps, field and arm connections to the motor . . . nothing strange found to explain the symptoms. Where else should I look, what else shall I test?

2

The pedals do wear out. Does the flat spot always occour at the same point / position in the travel?

Does it happen if you roll the trottle on slow or only when you hammer it? Or both?

Are you upgraded to HV lithium? My 10 eL (volt battery at 90v, long GE 5hp, 12.44:1, larger tires, slight frame lift) would trip a controller code if i hammered it from a stop and sometimes would “bog” or “flat spot” if i stuttered when I rolled it on. I found some old posts from @grantwest @MikeKC and @Inwo that indicated this was a glitch that was related to HV packs and driving style. The solution was at the time, dont drive like that.

3

Good catch. These use hall effect throttles. Much more reliable than the 2008 type.
Stuck brushes maybe?

4

This is what I would check.
@GemDandy - What motor are you presently using and when was the last time it was serviced?
Do you know how to check for a sticky brush?
When it is slow/labored, listen close for any unusual noises coming from the motor. It may sound like sizzling bacon in a covered pot. Intensity will vary with load and throttle pressure.

5

Thanks, I’ll take note as I drive and report when I’ve something definitive. Right now I’m checking the DL and DH modes, it SEEMS that the DL is smooth and limits me to about 100 amps of draw, and the DH is where it flat-spots with jumpy application of bursts of power.

R.

6

I do get a 19 mph flat spot and then it’ll push through it . . . sometimes.

Brushes; it’s a “Touched by Rodney” 7.5 long ventilated GE motor and an extended Range Lithium God battery pack . . . lithium (Di-lithium with 2X36 bolt packs.

R.

7

Here’s what this morning drive found. DH and hammer on to full throttle and it stalls out at about 18-19 indicated . . . consistently. It will not accelerate beyond that (almost never).

Switch to DL and hammer it on, and it smoothly accelerates to that same speed.

Disconnect the Magic Magnet and there’s no change in behavior.

Slow roll the gas pedal and it behaves the same. This is a new problem, it used to smoothly zoom up to about 30.

Brushes have been suggested, stuck. But is that really where I need to check next? What other test might I give it? Thanks for the suggestions and support so far.

R.

8

  • When you are 19mph indicated, What is car actually doing via GPS?

  • Is your battery charged? (Don’t overlook the obvious)

  • When was your motor last touched by Rodney?(how long ago?)

  • When you are running and hobbled, are there any other lights illuminated on your dash? (temp or turtle?)(don’t guess)

  • You mentioned that you checked connections- How did you check? (visual, tried to move/wiggle). Run the car hard, then get out and touch/feel for warm connectors).

  • Fasten your meter directly to your controller POS and NEG, and place it in a position so you can see it while driving. Tape it to your windshield for a redneck “Heads-up display”. What V is it seeing when maxxed out? Compare this number to what you App is sees coming on your battery. A big difference will indicate a connection issue.

  • Do you have any downhill runs in your test loop/hot lap around the block? Does it go faster than 18mph uphill/downhill? If no hills of significance - jack the front wheels up off the ground and run test. Does it indicate faster? (GPS speed will not be helpful)

  • What is the history of this controller?
    → original (never been touched) afuk?
    → sent to XX for reprogramming?
    → Recently?

9

Thanks. I’ve got my homework, will check back.

I live near Rodney if I need to check with him.

R

10

Startling conclusion of the mystery . . . bad field stud connection (broken field winding connection, or just hanging on by a thread). Kudos to Rodney’s keen eye. Temporarily switched to another motor and all symptoms went away and cart runs normally.

Thanks for the analysis and ideas.

R.