Navitas 5KW AC system with brake-modulated Regen - Photos

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Originally Posted by mattkovo

That is a great idea fstop! I put ausco rear brakes on my cart but haven’t been too impressed. They work great and I don’t lock them up like the drum brakes so that’s a plus. I was driving the other day and cranked up the regen to slow down and thought it would be nice if it was brake pedal operated. I’ll have to do give this a go. The regen braking was pretty impressive. Way more so than using brakes just brakes.

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You understand exactly what this is accomplishing, and I think you'd be very happy with any approach similar to this that makes those changes in real-time, with relative input from the brake pedal.

[twilliams81]

Originally Posted by WalterM6

You would be in a lot better shape if you adapted a Jakes Disc Brake System to it. 75% of the braking is done with the front wheels.

AMEN dude! I like simplicity because it usually LASTS LONGER!! lol This all sounds great in theory but I'm willing to bet you're gonna have problems in the long run..just my two cents.

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Originally Posted by mattkovo

It looks like the knob on the OTF controller is just a potentiometer. Have you thought about taking the controller apart and removing it to see how it is wired? I bet you could take the wires off the controller and hook them up to a sliding potentiometer. Then just attach the actual slider part of the potentiometer to the brake rod. The potentiometer would have to be in a fixed location and connected to the brake rod somehow. I’m not sure how much brake rod travel there is or how much travel the switch would have but I think it could be something to try. I have the AC Navitas also and think I’m going to try it out. I’ll let you know what I come up with.


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Obviously you understand that this isn't a topic about what kind or how many wheels brakes should be on, and you're exactly right - there are any number of ways to make this work. I considered multiple approaches, and ultimately decided to do it this way.

Since I wanted to make sure driveability was smooth and there weren't any unexpected consequences, I didn't want to destroy the OTF unit. They aren't that expensive, so I wouldn't think twice about going in and wiring around the pot, and then extending the pot to somewhere else or using a slider etc... since I now know the process works really well. This was one of the approaches I initially considered.

Also considered using an RC servo inside the battery compartment to actuate a similar mechanism to what I ended up using, but ditching the cable and using a servo tester (potentiometer driven) to drive the servo, connected electrically. Ultimately decided there more points of failure in this route, plus there were electronics involved. Nothing complicated, but more complexity.

Another way to go about it would be to use a similar, servo-driven approach but using an Arduino board and a fairly simple program written for same to interpret a 0-5v signal from a TPS or any generic pedal position sensor that would physically fit reasonably well and rotate the servo accordingly (RXVs have these built into their brake pedals).

This would allow a number of adjustments in software -vs- mechanical adjustments, and probably further flexibility in terms of keeping the servo from actuating during, say, the first 15% of pedal throw and allowing finer adjustment of that point (this is why I used semi-flexible wire section as link between potentiometer arm and 90 degree actuator arm - the slack in the link keeps the first bit of motion in the system from rotating the pot. More or less slack adjusts this amount, but it's a bit course...)

I'm sure somebody can create a cleaner and better design of this - but I wanted to post the concept and my implementation of it to start the ball rolling, as I haven't seen something like this done before that I'm aware of.

In a perfect world there would be a small position sensor available that fits with only simple modification to the brake pedal assembly and a 3-wire harness that connects this sensor to another port on the back of the OTF (or controller), and a 4th knob on the OTF (or at least a parameter in the App) that allows for adjustment of "Braking Regen Strength". All nice and neat, w/out any mechanical (except the position sensor, technically) linkages.

Bottom line is what's missing from the Navitas AC drive system (IMO) as it relates to Club Car is only being able to adjust off-throttle regen, when there is significant benefit to being able to adjust both off-throttle regen AND active braking regen, independently. And since Club Cars (or at least the Onward models, Precedents and DS models also, I think) don't have any way to relay driver braking feedback to the controller, I had to come up with a way to do that.

*It could be that the new factory AC drive Club Cars have a brake pedal position sensor - I don't know since mine is a 2018 that I pulled out the SEPEX system from and replaced with Navitas AC. If the new factory AC carts DO have a sensor on the brake pedal, there still is no input for this on the Navitas, but it could still possibly make it easier to facilitate what we're talking about here. I'll add that I can read "brake voltage" in my Navitas app, but it is always 0, but there could be unused pins on the big molex that connects to the Club Car harness where you could input signal modulation of 5v. There are also braking parameters in the app that go unused (they aren't even greyed out) that are clearly for the RXV version, so possibly the current FWs may even work if you could get the 0-5v signal into the controller. I seem to remember the RXV controller having a different Molex with more pins, so all of this would be well above my pay grade and probably unlikely to work anyway, but it could provide a much more elegant implementation.

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Originally Posted by twilliams81

AMEN dude! I like simplicity because it usually LASTS LONGER!! lol This all sounds great in theory but I'm willing to bet you're gonna have problems in the long run..just my two cents.

Your point is well taken, but the purpose of the topic really isn't what kind of brakes are the best, or will last the longest, or are more or less mechanical than other kinds of brakes etc... and is really mostly relevant to Navitas AC drive system users.

That said, you could easily be right about long term use - but I don't think I mentioned that I thought this would last forever (what does?). But then again, it could - and it's certainly simple to adjust / fix / replace.

[mattkovo]

You brought up some interesting ideas on the implementation side. I’m going to do some research before I jump in but will for sure get something like this going. It will make the cart fee a lot more powerful when braking.

[Bobbob]

fstop thanks for posting info on regen operation. I recently purchased the AC motor and controller. Have not installed it yet on my cart but good to know other people are thinking about modifying the system.


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[greg-g]

I like this approach you were thinking out of the box. so installing a pot box or throttle position sensor on the brake pedal or maybe just a switch and a fixed resistor would work just as well and have less mechanical movement.

again great thinking and great job

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Originally Posted by greg-g

I like this approach you were thinking out of the box. so installing a pot box or throttle position sensor on the brake pedal or maybe just a switch and a fixed resistor would work just as well and have less mechanical movement.

again great thinking and great job

I think you're right - there are any number of ways to make use of this.

I've put some miles on it now, and braking is ridiculously good if you need it to be, and mild otherwise. No jerkiness, nothing unexpected, just solid, controlled and increasingly authoritative stopping as you continue to push down.

Though I love my 52v pack, I've been considering 72v but one of the main reasons I keep kicking it out of my head is that even with 52v the braking wasn't really sufficient for higher speeds in this cart if you got into a situation where you needed to stop fast. Speeds from 72v would only make it worse (I don't drive fast in general, but do like to here and there when I'm in the right areas for it).

The added stopping power, control and feel with this setup makes brake inadequacy a non issue IMO. Yes - you need to be very careful in high speed carts - and that won't change, but speed won't be way out of kilter with braking capability.

I'm interested to see how others here might take the concept and improve, simplify or alter it.

I haven't asked Navitas anything about being able to get a signal into the controller, or if the "Braking" parameters will function on the Club Car implementation of the TAC2 if it has braking feedback to work from, but maybe I'll send them an email. I doubt they'd want to get involved though.

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As a follow up, Navitas tech called me about an error I had reported to them in one of the apps, and after straightening that out I mentioned this approach to regen braking and asked if there was a way to get an analog signal into the controller. They were very interested in the concept, and said that yes there was a way, and would likely involve sending the controller back in for a different connector to be put on. He also indicated they are considering offering accessories for the controller, and they may possibly add input capabilities.

So it looks like a more elegant way to do this is possible - I'll report back with any news I get. In the meantime, my mechanical approach has been working great - no issues.

[Left Coast Kiteboarding]

I'm with you on this. Gotta be done. I 'm hoping the the input from the regen knob is somewhere close to the same as an MCOR box. would be silly easy to mount another MCOR on the opposite side of the buggy and use it to drive the regen. IF not I'll just have to come up with some other mechanical setup. I fully agree that the regen braking of the Navitas is enough for almost all braking needs. The fact that you have done it and the performance is good simply means that those of us that follow will just need to improve in the execution. WELL DONE!!