Electric Granddaddy Prep

[J123]

Hi Everyone
Gearing up to start an electric kart project for the kids (and myself of course). Looking at it as a good way to practice my welding skills and challenge myself. I couldn't find too many two seater designs with suspension out on the net, so as of right now I've settled on the Spidercart GrandDaddy for a chassis. It will require some modifications to go electric of course. The plans look reasonably well detailed. As I'm starting to pull together a plan and estimated costs, wondering if the more experienced folks could weigh in on some drivetrain questions:

I'm looking at motors in the 5kw range. The two that I'm comparing are the:
5KW Golden Motor Brushless and the Motenergy ME1717
There is about a $200 difference between the two. The Motenergy looks like the better product and the IP 65 rating is a nice feature, but wondering if anyone has experience with the Golden Motor and their controllers.

Some questions:
- Is the cost to upgrade to the Motenergy worth it here?
- Any quality concerns with the GoldenMotor products?
- GM offers a liquid cooled version, under what circumstances would this be needed? Since I won't be running the kart full out for extended periods of time, I'm assuming air cooled will suffice. Geeking out on liquid cooling sounds fun though.

Now the battery:
- Not sure I want to drop the money on it, but what are the thoughts on this ReLion battery?

48V Lithium Golf Cart Battery | RELiON

InSight Series is a 48V lithium battery designed specifically for golf cars, utility vehicles, and AGVs.

relionbattery.com

30ah, but shows a 100A continuous discharge rate and 200A peak . If I'm doing my math right (am I?), it would provide about 17 minutes of power at a continous 5kW. So in normal use, maybe 45 minutes to an hour of playing around? Does this seem right?

For the motor controller I'm considering the Golden Motor, Kelly, or Sevcon (although seems unnecessarily pricey compared to the other 2)

Let me know what you all think. Am I making some bad sizing choices here?

 

[EpsilonZero]

I run a ME1717 with that exact RELiON battery and a Kelly controller and have run various combinations of sprockets (12, 14t motor and 54, 58, 60t axle) for speeds up to ~52.5mph with my kart.



Maximum battery discharge can get up near 300A briefly, but continuous discharge is better than 1:1 MPH/Amp most of the time while cruising with my current 12t/54t setup (i.e. well under 25A drain @25mph on flat ground, constant speed). You won't be cruising around at 100A discharge unless you are running ~50mph the whole time (I saw numbers like this only with 14t/54t setup). On my last 80%DOD ride (ride until 20% left), I did 26.45 miles at an average of 22.8mph. You can easily drive more than an hour on one charge. If you drive very aggressively with lots of drag racing type runs (dead stop to max speed), you will drop some range but I have never blown through 80% battery in anything near 17 minutes; more like 45 minutes with very aggressive driving. This is all with a total weight of around 470lbs with driver.

I looked at Golden Motors but I think they use a metric shaft size and I had trouble finding a supplier for the motor sprocket at the time. I actually went ME1305 first then switched to the ME1717 for the better efficiency, quieter operation (no fan), and IP65 rating (stops dust and water). The ME1305 is a good motor that a lot of people run (or often the older 0907), but it is sitting in my garage for now. Note that the ME1717 comes with phase wires installed.

With the RELiON 48v (51.2v), I ended up using a Grin Cycle Satiator as my charger. The golf cart charger they had been recommending and shipping with their sets of two batteries was no longer recommended by them and I have not tried their current recommendation, but I had to return the one I originally bought because it wouldn't charge (I only bought one battery). The Grin is user programmable and I would HIGHLY recommend it (get the standard 8A version). Also, get yourself a coulombmeter to monitor your lithium battery charge. I have one installed in my dash.

Here are a couple of videos of the kind of performance you might see (first is a 360deg video, so you can look around)

*edit: I said ME0907 instead of ME1305, the all-aluminum chassis unidirectional fan version...

 

[J123]

That is a sweet setup Epsilon! Thanks for the awesome reply. Gives me some confidence that I’ll be in the right performance spot even though weight will likely be more than double of your cart. If top speed is 25mph I’ll be plenty satisfied. I’m a bit confused on how to determine if the motor will have enough torque. Where I‘ll be using the cart there is a fairly steep grass hill that I want to make sure it can make it up without straining. Is there a torque curve for the ME1717 somewhere? Any good resources for estimating performance based on weight, sprocket ratios, etc?

 

[EpsilonZero]

I'm not one for running through the formulas (itsid might be able to help there), but as far as I know the rated torque is 9.55Nm for the ME1717, which is better than the ME1305 (9.2Nm... oops, I said 0907 earlier - 1305 is the updated version I got). The ME1717 is near best in class for off the shelf Motenergy single stator motors from what I've researched. There is definitely a difference in the seat of the pants for me between those two. We don't have hills around here, but steeper overpasses don't slow the kart down at all. I think there are other motors that have higher torque in general, but I don't have experience with them (mostly two stator ME motors and all near double the weight). The ME1717 is more unique with the 5500 RPM max (instead of 5000), sealed design, and lighter weight than all other ME motors at 20.5lbs.

You won't be limited to a top speed of 25mph unless you severely limit your max RPM (~3800) or have a massive axle sprocket spinning in a trench below your kart. About the highest ratio you can physically achieve without a jackshaft is 5:1, which is going to get you 39.4mph with a 12" tire (12t/60t sprockets) or 32.86mph if you limit to 5000rpm. I would suggest that ratio for offroad and hill climbing to minimize strain and maximize torque. Gear Ratio Calculator

If you want more specifics on the ME1717, here is the performance curve chart. Performance Curves

 

[J123]

Just looked up that Grin charger, very cool, and I think you answered my question for what charger to go with. Looking like this would work good, now I need to order some steel and get to work! Sorry if you've already covered this before, but are you using a potentiometer throttle or hall and does it make any difference? Do you have regen enabled?

 

[J123]

One more question as I pull together the parts list...what capabilities does the CAN Bus option on the Kelly Controllers provide? Assuming this allows data communication for real time status?

 

[EpsilonZero]

Just looked up that Grin charger, very cool, and I think you answered my question for what charger to go with. Looking like this would work good, now I need to order some steel and get to work! Sorry if you've already covered this before, but are you using a potentiometer throttle or hall and does it make any difference?

I use a hall-effect pull throttle mounted in the rear and have it spliced to my mechanical throttle pedal (same as you'd use for a regular engine throttle). I only used a potentiometer for bench testing, but I am happy with my hall-effect throttles on my karts.

Do you have regen enabled?

I have regen enabled at ~40%. My mechanical brake and regen brake (just switched on/off) are operated on the same mechanical pedal. I very rarely press hard enough to activate the mechanical brake. The regen brake is powerful enough to lock up your wheels at any speed on dry pavement if you set it high enough. My regen brake switch installation may seem a little weird, but it has been rock solid for many hundreds of miles.

One more question as I pull together the parts list...what capabilities does the CAN Bus option on the Kelly Controllers provide? Assuming this allows data communication for real time status?

I haven't used CAN bus functionality on the controller or the battery. Fany Chen at sales@kelly-controls.com should be able to give you detailed information about controller functionality if it isn't in the documentation of the controller you want.