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Old 11-05-2021, 08:38 AM   #1
fstop
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Default L4 / L6 with Navitas AC / 600A?

I normally stay in the CC forums (as I have a CC) but am curious about EZGO users with 72v carts and the Navitas AC set up.

I've had mine for 2 years now and generally like everything about it, but since going to 72v about a year ago, have discovered an issue that only exists (as far as I can tell) with 72v applications.

Navitas says nobody else using 72v has ever mentioned it, but I know that other users I've spoken with have exactly the same issue, and that is an issue where accelerating hard or moderately after decelerating / coasting down to 7-12 mph or so (23" tires in my case) causes violent shaking / gear lash upon initial re-acceleration.

There is also a frequent hesitation (w/out the shaking) in this same scenario if you don't decelerate down too low in speed before accelerating again (12-14 mph). I have an in dash GPS so am familiar with speed points at which things happen.

The odd thing is that any form of acceleration from a stop, everything is normal - and great. Same situation if you coast or decelerate, then re-accelerate, but just don't let the speed get down below 13-14mph or so before you do. All great there.

This issue was not there when I had 48v lead acid, or my ~52v lithium battery. Changing to 72v lithium and it appeared. I've tried numerous FW updates and versions, and been through it with Navitas - they continue to tell me I'm the only user that has reported this.

The shaking issue I found out (not from them - they never suggested it) can be eliminated by reducing the "Acceleration Ramp Rate" (in the Off Road portion of the app) way down from default - 200 in the Club Car version.

The problem is that reducing this value far enough to eliminate the violent shaking and gear lash increases the hesitation problem.

Anyway, as I understand it, all L4 and L6 carts (at least with lead acid batteries) are 72v, so I'm posting over here, as there aren't many CC users with 72v. I've spoken to at least one CC user that has been using 72v first in lead-acid and now lithium, with the identical issue remaining.

I generally love the system and especially the simple adjustability of it, and it is possible to adjust around it somewhat, and also adjust how you drive it to get around it somewhat, but any observations would be welcome.
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Old 11-05-2021, 09:28 AM   #2
Scott quail
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Default Re: L4 / L6 with Navitas AC / 600A?

Ive seen this before but was not a navitas controller but a curtis and the issue was resolved by adjusting the Negative field gain in the parameters. Im not sure how you can change that in this case or if its even an option. Same issue though. Cart would run normal except for re-acceleration it would jerk. It felt more like a loose connection but finally figured it out. Im not too familiar with navitas controllers but maybe you can change settings? Im not sure.
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Old 11-05-2021, 12:48 PM   #3
fstop
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Default Re: L4 / L6 with Navitas AC / 600A?

Quote:
Originally Posted by Scott quail View Post
Ive seen this before but was not a navitas controller but a curtis and the issue was resolved by adjusting the Negative field gain in the parameters. Im not sure how you can change that in this case or if its even an option. Same issue though. Cart would run normal except for re-acceleration it would jerk. It felt more like a loose connection but finally figured it out. Im not too familiar with navitas controllers but maybe you can change settings? Im not sure.
Interesting - thanks for chiming in. Was the Curtis an AC controller?

The FW on these is definitely not optimized for 72v at this point WRT to re-acceleration, but the rest is pretty much spot on.
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Old 11-06-2021, 08:38 AM   #4
Scott quail
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Default Re: L4 / L6 with Navitas AC / 600A?

Yes. It was an AC drive.
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Old 11-07-2021, 08:08 AM   #5
fstop
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Default Re: L4 / L6 with Navitas AC / 600A?

Quote:
Originally Posted by Scott quail View Post
Yes. It was an AC drive.
Ok thanks. Was it also a situation where it was fine until input voltage was increased (48 -> 72 in this case) ?
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Old 11-08-2021, 10:41 AM   #6
Scott quail
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Default Re: L4 / L6 with Navitas AC / 600A?

Not in this case it was not.
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Old 11-08-2021, 02:15 PM   #7
fstop
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Default Re: L4 / L6 with Navitas AC / 600A?

Thanks - hoping Navitas will take the time to look through the coding...
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Old 11-15-2021, 03:58 AM   #8
luvdamud
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Default Re: L4 / L6 with Navitas AC / 600A?

Fstop, my Cushman (EZ-GO) 72v does not have the issue you are referring too. I ran the Navitas TAC2 600 with my old FLA batts for months before upgrading to lithium. I have not experienced the issue you are referring too either before or after the Lithium pack.
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Old 11-15-2021, 08:33 AM   #9
fstop
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Default Re: L4 / L6 with Navitas AC / 600A?

Quote:
Originally Posted by luvdamud View Post
Fstop, my Cushman (EZ-GO) 72v does not have the issue you are referring too. I ran the Navitas TAC2 600 with my old FLA batts for months before upgrading to lithium. I have not experienced the issue you are referring too either before or after the Lithium pack.
Thanks for the feedback. How heavy is this cart and what gearing / tires does it have? Also, have you specifically tried standing on the go pedal after decelerating down to 3 or 4 mph? What tac2 settings are you running?
Thanks!
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Old 11-24-2021, 04:55 AM   #10
luvdamud
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Default Re: L4 / L6 with Navitas AC / 600A?

Fstop, the cart is between 1000 and 1100lbs with the lithium battery. I have stock 20" tires and 16:1 rear and yes, I have slowed to very low mph and floored it many times. I love how it throws gravel when floored.

As far as your hesitation, I did experience that some due to voltage sag when my lithium pack would start to get low. I have a custom battery config using one of the lithium profiles (as told to do by Navitas) but when my pack would get low, a high amp acceleration run would make the voltage sag and the Navitas would throw a low voltage error and then immediately go away. I had to do a screen capture to actually catch it happening. I lowered the voltage in my config and that problem went away. It took a little trial and error to catch and to be honest, if I wasn't running the Lithium config in the Tac2 it probably would not have happened.
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