Jerky acceleration -where do I start!

[acem8]

Hi guys, I have searched high and low for some answers but it appears this could be one of half a dozen things. I am a mechanically/electrically minded engineer but this is all new to me.

CC Precedent 2016 purchased in October with new batteries. Worked great for 6 weeks and then started to jerk on acceleration a few days after being used for 27 holes (but fully charged overnight). Here are the symptoms to try and narrow it down;

- Pumping the pedal 30x does not seem to help possibly ruling our MCOR.
- Happens in forward and reverse.
- Doesn't matter if it is at the start or end of the round.
- If I very carefully wait for the click of the solenoid I can get it moving smoothly but it will still have some jerking before getting up to full speed.
- Pack voltage is good but I haven't had the chance to test it under load yet.

On Friday evening I took it for a test drive down our quiet road and up and down a steep driveway with no problems getting it up to full speed. Went out on the course on Saturday which was very very wet and it played up from the 1st hole. Our 18th hole is straight up hill and it would normally struggle but on Saturday it was cart path only and it flew up there. Could this be wheel spin/clutch related or was that purely due to lower rolling resistance?

Much appreciate any help before I start guessing at which component to change first.

[acem8]

I've just been checking the voltages and I have 8.5-8.6V on all batteries 5 days after charging which seems good. I put it on charge because I need to use it tomorrow and noticed the 3 batteries on the driver side are charging at 10.8V but the 3 on the passenger side are 9.9V. This is near the end of the charge, earlier there was a bigger differential. Is this normal?

After playing tomorrow I will make up a lead and test it under load.

I also added some INOX MX2 battery conditioner which is supposed to reduce sulphation. They are an Australian company with a good reputation so I will report my findings. All I can find out is it contains less than 5% cadmium sulphate and the other 95% is non-hazardous 'secret' ingredients.

[acem8]

I don't intend to keep bumping my own thread but I have made some progress with this and the information may be useful to others having the same problem.

MCOR resistance tested ok and jumping the 2 pin made no difference. Disconnected the leads from the large terminals on the solenoid and in RUN-Key on-Fwd there is a noticeable double click. If you hold the go pedal really steady it is possible to get 10 seconds before it clicks off. Maybe when driving and there is current flowing through it can hold for longer but it is consistent with the driving experience.

From reading other threads the Sepex controller needs to send ground to the solenoid (small terminals) an unless a number of conditions are met this will not happen. Pin 5 needs to measure +30V and mine only measured 25.6V -this is the charger interlock which stops it being driven while charging. I am also measuring 25.6V at the charger receptacle (blue wire). Sergio posted previously there is a 10K 'pull up' resistor to get that voltage up to 48-51V when the cart is not being charged.

I am hoping/praying this resistor is the problem and the next step will be to find it. I assume I have to take out the 2 central batteries and remove the panel that the controller and solenoid are fixed to.

Will update in the next few days.

[simicrintz]

Posting up your findings as you go is awesome and definitely helps others; very cool!! In addition, it keeps the smarter folks (I am not one of them!) abreast of what you are doing and seeing, giving them the potential to jump in and help.

Keep up the good work!!

[scottyb]

Originally Posted by simicrintz

Posting up your findings as you go is awesome and definitely helps others; very cool!! In addition, it keeps the smarter folks (I am not one of them!) abreast of what you are doing and seeing, giving them the potential to jump in and help.

Keep up the good work!!

[DaveMJ]

I had this occur recently, tuned out the motor brushes were severely worn.

[Lochlin]

Originally Posted by DaveMJ

I had this occur recently, tuned out the motor brushes were severely worn.

Yup. Is this an AC or DC motor. Sorry, but I don't know modern Club Cars at all. I do have some older carts, though, all DC, and bad brushes do exactly what you describe....herky jerky until the brushes are too worn for even that much.

If your cart is AC this all goes out of the window of course.

[acem8]

Thanks guys, I won't rule out the motor because I haven't checked it yet...

I did some electronics at school so it has been interesting to look at the circuit diagrams and work out how these carts function. My theory is the charger interlock input to the controller is close to 30V hence the intermittent nature of the jerkiness. When the pack is under load (moving off or going uphill) the voltage probably drops to under 25V and cuts off ground to the solenoid. My first check will be to put a jumper from the key switch to charger interlock to see if that solves the problem before I go searching for the reason why the voltage is low.

[acem8]

FIXED

I took out the 2 middle batteries and removed the access panel to try and find the pull-up resistor for the charger interlock. I noticed the B- terminal on the controller was loose - to the point where the spring washer was completely open. Played 18 holes yesterday and it drives like new - I am really happy that it cost precisely $0.00 to fix!

On initial testing with the solenoid disconnected it was still clicking on and off and the charger interlock was sitting below 30V which I can't work out. I did read from Sergio that the impedance of a DVM might measure the voltage across a resistor incorrectly? Anyway lesson learnt - check ALL your ground connections first before looking at the MCOR, solenoid, speed sensor, batteries or controller.