Erratic speed after brand new batteries installed

[nkamar]

I own a 2000 Series TXT that is heavily modified (SR48500 tuned by ScottyB for max torque, HD solenoid, SW202 reversing contactor, Admiral Mot-B1 motor, 2 gauge cables throughout). I was previously running it on 48 volts with eight 6v batteries. I have been running it like this for a whole year without any problems at all! Just a week ago, I decided to sell the batteries and go with six 8v Trojan T-875's, and now the cart is unpredictable. With full throttle, sometimes the speed goes to a maximum 20+ mph and sometimes it only goes 10 mph. The worst part about it is that it seems very random, so the wife is now complaining about the jerkiness when it all of a sudden speeds up. Voltage on the set of new batteries is around 51-52 volts.

I have read previous posts about a battery break-in period and am currently following Scotty's suggestions on his website. Scotty is usually very fast to respond to e-mails, but I haven't seen anything about this on previous posts and want to help someone else who may be experiencing similar problems.

So, is this a normal part of the break-in period or do I need to look into getting something fixed? If this is normal, will it correct after 10-20 cycles (when the break-in period is over)? Thank you everyone!

[cgtech]

It's not related to battery break-in. I would suggest hooking laptop up to monitor throttle signal indicated in controller. I have seen weird things happen where just clearing the throttle calibration solved it (hit "clear auto cal" in software drop down menu.

[mutant]

test each battery under load to see individual voltages,especially during the surging... check all high voltage connections....these may be voltage fluctuations or bad signal inputs to the controller....

[scottyb]

Sounds like a problem with the throttle signal, I doubt it's a battery problem.

Can you connect to the SR controller and monitor the throttle signal ?

[nkamar]

All batteries test well under load. I tried resetting the auto calibration. I really can't tell if it's better or not, but the problem still occurs. It seems like maybe it's going in the "fast mode" more though but it's still not the same... I don't know if it's helpful, but there does not seem to be a smooth acceleration. It's almost as if the cart runs up to a certain speed and then when depressing the pedal just a little bit more, it suddenly lunges forward and even peels out while in motion!

I have attached the computer to it when it's not moving. Pardon my ignorance, but are you suggesting to hook up the laptop while I'm driving? What am I "monitoring" exactly?

Thanks again everyone!

[JohnnieB]

Originally Posted by nkamar

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I have attached the computer to it when it's not moving. Pardon my ignorance, but are you suggesting to hook up the laptop while I'm driving? What am I "monitoring" exactly?

The problems are occurring while driving, so you need to monitor while driving.

You'll be watching the Throttle % and looking for things like erratic changes while the pedal is being held steady.

Have someone drive cart while another person watches the laptop screen.

Additionally, have the laptop log the controller data to a file so it can be reviewed later.
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Erratic throttle issues are often related to moisture in the pedal box or dirty connections in the in-line connector between the cable from pedal box to carts wiring harness.

[kernal]

Did you happen to wash the cart when changing out the batteries?

[nkamar]

No, I haven't wash it for a while. Here's what I came up with... The increased speed (surge that causes my wife's head to whiplash :) ) occurs at different throttle percentages. Most of the time it's around 80-85%, but sometimes it occurs in the 30 to 50 percentages and sometimes it still does not surge at all (explains for the 10 mph top speed at 100% throttle). Seems kind of random.

I guess I'm beginning to think it may be a problem with the controller, but what are the chances that the controller goes bad at the exact same time as changing the batteries? I guess one good thing (and something I can rule out) is that the controller seems to be picking up the same throttle percentage as what the foot pedal is telling it!

[scottyb]

Most likely that none of this is caused by the batteries or the controller.
Jack the cart up so at least one rear wheel is off the floor, remove the seat and connect the lap top.
Connect the laptop and open the Monitor
Put the cart in neutral and see if the controller LED will light up when you press the gas - if not move the F&R ms red wire to the same terminal as the blue wire. These 2 wires are on the same ms closest to the driver, basically you are bypassing the switch - the controller should light up when you press the gas but the wheels will not spin. This is what you want.

Okay now monitor the throttle signal through the throttle pedal range several times. If the signal is smooth without variation then the problem could be a loose connection or very rare = in the controller ?

[nkamar]

I finally figured out the problem! I feel a little though...

When I couldn't figure out what happened, I decided to move my 36v reversing contactor from 40v to 32v. Since it seemed to be working well going forward and reverse, I just left it this way Big mistake!!! If I left it on the 40v and then cleared the throttle calibration then I bet it would have worked perfectly. Instead, I went through a long frustrating process (changing the ITS sensor, redoing good wiring, replacing cables, etc). BIG thanks to Scotty for helping me through it and not getting frustrated with my many e-mails!!

Got the contactor connected back to 40v and it now works perfectly again! Thank you everyone for all your help! This forum is