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

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I've had the Navitas 5kw AC motor / Tac2 600a controller for some time now in my factory lifted 4-passenger Onward.

The brakes in these carts just aren't great. Mine are perfect and properly adjusted etc, but they are just marginal.

After going with lithium power and the added speed that brought, despite the 317 pound weight loss the brakes are still an issue.

I don't like aggressive Regen. Don't like the jerkiness and the wear / tear on the rear-end that can come with aggressive amounts of it.

I like the RXV's approach to braking, in that it modulates Regen to get this done.

I was thinking wouldn't it be great to have the Club Car mechanical brakes, but to additionally have increasing amounts of regen be applied as you continue to push the pedal further. Esp. in a panic stop or coming up on a turn you decide to make last minute.

The key for me though is having moderate / low amounts of regen at all other non-stopping times, to reduce need for slight braking, and keep you from switching your foot over all the time from Go to Stop pedals, but avoiding the overly jerky character that comes with it.

So, I devised a pretty simple way to proportionally physically rotate the Regen amount knob on my OTF control (which I never used) so that normally, it stays at a pre-set amount (10% in my case, but can adjust this point), but when the brake pedal is depressed more than about 5/8" inch of travel (also adjustable), it begins to rotate the Regen knob, increasing the amount the farther you push down the pedal. A full panic stop pushes the Regen to around 60%.

This works AMAZINGLY well. I really had been putting off the experiment, assuming there would be issues, and things were OK w/out doing all of this. But I spent some time and knocked it out, and I'm extremely happy with the results. This thing stops so smoothly, and with very modest pedal pressure.

I tried to "engineer" (if you want to call it engineering - more like monkeying in the garage) an adjustment for as many parts of the system as possible, knowing that I'd need to adjust throws, amounts, cut in points, etc... I knew I didn't want it to cut in as soon as you touched the brakes (though I can adjust it to do that), but only after going beyond slight mechanical braking pressure would it start to kick in.

I'll also add that this is inherently fail-safe, as in mechanical brakes still function just as before, and consequently, if any part of the regen operation linkage breaks, it doesn't matter. Also can't jam or stop any part of the original mechanism - it's all lightweight model RC airplane linkage parts - they'd just break, and thats the way I wanted it.

I can't re-iterate what a difference this made. A properly engineered 5v brake position sensor and the appropriate input on the Navitas controller would be the way to do it, but this works perfectly, if a little primitive.

Somebody with a 3D printer could make a custom regen knob for the OTF with control arms all integrated, and also streamline some other parts I had to cobble together. Certainly further refinement is possible...

A picture is worth 1K words, so here they are.

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... and another showing the control linkage exit from below the brake pedal assembly, through the plastic housing.

Additionally, here is a (somewhat jerky) animated GIF of operation...

EDIT: Well apparently the GIF doesn't work on the forum, so here's a link to a short video of it.

https://www.dropbox.com/s/bobcj6abnv...85722.mp4?dl=0

[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.

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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.

I specifically wanted to avoid adding more mechanical brakes.

Efficiency has been an important part of the equation (hence AC drive system), and while I haven't driven a cart with additional front mechanical brakes, I'll go out on a limb and say I'm not sure it would handle quite like this does. I like the high regen resistance feel when braking - I'd say it's more like downshifting / compression braking your car (for those who know how to drive a stick shift - not so common these days) -vs- pushing in the clutch and using the brakes. It's a different feel, but both ways will slow you down.

I'm sure they work well though, and that's a great alternative for those that don't mind the weight, complexity and cost, or have a drive system that offers substantial regen braking potential.

[Budule]

Well that was a nifty way to get there.....Are you perhaps related to a Mr. Goldberg ?

[WalterM6]

The Jakes Disc Brake System is hydraulic.

[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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[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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[CCNorth]

Originally Posted by Budule

Well that was a nifty way to get there.....Are you perhaps related to a Mr. Goldberg ?

Now that's funny!

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Originally Posted by WalterM6

The Jakes Disc Brake System is hydraulic.

I understand it doesn't use a cable like the factory drum brakes, however hydraulic is still mechanical - squeezing one thing against another thing to cause friction.

Disc or drum brakes are both mechanical braking devices, whether actuated via hydraulic pressure or cable pressure.

They both slow down a cart, and both make heat in the process, whereas regen slows down the cart but makes electricity (albeit not a whole lot).

I've got nothing against anybody's front brake kits, or the effectiveness of them. Using them really has nothing to do with the intended concept of my post though.