EZGO RXV stops after hill descent

[markp63698]

Have a 2014 EZGO RXV just purchased from a dealer. I live on a hill and its a steep descent for about 1/4 of a mile. So my day starts with a fully charged cart and the downhill ride and the cart is braking most of the way. Near or just at the bottom the cart stops and brake locks. Had smell on one occasion. turn the key to N and switch to tow. After about 4 or 5 min the brake releases and all is fine.

Too much hill and the brake overheats? Safety mechanism working or is something defective.

Thanks for your help.

[dougs_huntingcart]

probably...
If you just slightly your foot on the gas pedal you'll still have a controlled decent. The cart will work to maintain your desired speed and may not need to utilize the brake as much. This cart takes some getting used to if you've driven a cart that will just free wheel down hills.
My foot is always into the gas and have an approximate glide for the last part until I need to brake. Like an approach shot into the green...lol .

[mjroman20]

Does the solenoid not close?

The RXVs have a resistor to burn off excess regen current. The driver for it activates when the battery voltage hits a certain level - i.e regenning with a near full battery. In this case you will be putting about 60~70V through a 0.42ohm load to B-, it will get hot. When it heats up enough the bi-metal switch on the plate covering the resistor opens and disconnects the solenoid coil so it cannot close the contacts. This results in:

A) the vehicle not running with pedal input until it cools off.
B) cutting loose the regen current if still going downhill to prevent battery/controller damage.

Depending on which controller is in there you should be able to modify the PWM on the resistor as well as the turn-on voltage. Lowering the PWM should help with the heating but I don't know enough about batteries to say for sure how detrimental this will be to them.

[markp63698]

Thanks Gents. MJR's analysis seems to be exactly what is happening. The dealer just got back to me and suggested to replace the brake. Sending the replacement today so will give that a try. Your right, takes getting used to versus my TXTs.

Today i stopped twice during the drive down for a few minutes each and was able to get to flat ground and ran fine.

[cgtech]

The motor brake is not the problem, it's job is only to hold the cart still After it has come to a complete stop. But the high battery voltage/burn-off resistor does seem like a likely culprit.

[markp63698]

Thanks CGTech,

Appreciate your thoughts and please help me to follow a little more. Went down again and stopped 1/3 way to see if the resistor was getting hot. It was not. Then continued for another 30 seconds and stopped again and this time the resistor was hot. I believe this suggets the regen brake initially was charging the batteries but then later into the trip the braking energy went to the resistor. So all of this suggests the resistor cannot dissipate the braking energy and the safety cut off the stop the cart....and then the parking brake locks because I am on a hill.

So do you agree all working correctly....just too much hill when going down with near or fully charged batteries?

[mjroman20]

This all sounds correct to me. The parking brake is supposed to close when 0 throttle is requested and the vehicle speed is under the threshold RPM, usually about 300ish. If you were not quite at full charge then the first third of the hill gave you enough regen to 'top it off' or if it was not as steep as the following section then it may not drive the resistor quite yet.

The units I have looked at all seemed to have a default turn-on voltage of about 67V. This means as long as the voltage detected on the KSI and CAP bank remain under this value the resistor will not be pulsed. If these voltages exceed this value then the RES post driver will pull the resistor to ground to bleed off that excess voltage. If you have a curtis handset you should be able to monitor the KSI and cap bank voltage as well as the resistor PWM.

You can check the functionality of this driver too by turning that turn-on voltage setting down below the actual pack voltage. Though I dont recommend this unless you can quickly get it back up over that threshold.

[markp63698]

Many thanks. Will wire a volt meter to monitor when the resistor is 'pulsed' as I make the decent to learn more about when I start getting into trouble. Could put a led/light indicator (rated for 70v) in the dash which is across the resistor in the longer term.

[cgtech]

Yes, this sounds correct. There used to be a kit for earlier danaher rxv that added a second resistor to solve this exact problem. You seem to have found a rare problem, but a problem that has happened before. The way that the resistor is now plumbed directly through the controller means this kit wouldn't work with newer Curtis RXVs. Maybe a possible solution is to adjust the allowable ratio of on vs off for the resistor, since it is only engaged for one hill at the start of the trip (current ratio is 2/3 on/off). Another solution may be just go slower down the hill.

[markp63698]

I am still wrestling with my 2014 RXV dissipating regen braking to the resister when going down from my home via a steep hill on a full charge. I installed a LED across the resister which tells me when this is happening. I only have about 15 to 20 seconds and then the safety switch locks the cart for 3 to 5 min. At least now I can stop the cart before lockup and let it cool for a few min in a safe location.

I connected a Curtis 1313 Dealer level handheld and do not see any programming options on regen braking. (Curtis 1206 Controller) After review online it appears regen braking is setup the same in all Profiles and not adjustable.

Sound correct? Can an OEM level 1313 get to regen braking? I'd like to use the foot brake a little if needed when making the descent. Right now, I never use the foot brake as regen is always slowing the cart quickly.