EZGO TXT Super Cart project

[Tsteak]

Originally Posted by JohnnieB

Motor RPM:

At 40MPH with 8:1 gears and 20.5" tall tires, the motor spins at about 5250RPM.

The max recommended RPM for your motor is probably 6000RPM or 6500RPM, which translates to 45.7MPH or 49.6MPH respectively, so you probably don't want to exceed those speeds going down hill.

Might want to contact motor manufacturer to get actual max RPM for your motor.

Controller temperature:

The monitor page and data log lists two temperatures, M- and B+
The MOSFETs that feed amps to the motor (PWM output) use the M- busbar as a heatsink the M- reading is how hot those devices are getting. The controller shuts off when the M- busbar exceeds 85°C (185°F).

Total amps that flow through the controller enter the B+ busbar, so it may run slightly hotter than the M- busbar. Not sure if the is an over temperature shutdown for this busbar.

Cable temperature:

I advocate no more than a 10°F rise above ambient (air temperature) for the high current cables, but 2Ga cables ought to be sufficient. Of course, it depends on how many amps are flowing and for how long.

The number of amps drawn by the motor is determined by the motor's RPM. The lower the motor's RPM, the more amps it is capable of drawing and with taller than stock tires and a numerically lower than stock gear ratio, your motor is spinning 43.5% slower than a stock drive system. Depending on the whether the carts is traveling at near top speed, low speed, or something in between, at the lower RPM the motor may be drawing 200% to 300% more amps, maybe more.

Record a data log and post it here so we can see how many amps are being drawn. (You'll have to zip the .csv file and attach the .zip file to a post).

Also might be bad connectors on the cables, or bad connections. If you have a IR thermometer (aka non-contact), measure the temperature of the ring terminals and connections vs the central part of cable.

Johnny, thank you, you are a wealth of knowledge! Motor is rated for 7000 max, so I'm very happy to hear your numbers on that.

I shot the terminals yesterday and got a reading of 110*+ while I was testing and changing settings; it was 85* outside. I was able to get the two modes operating the way I wanted, and it seems to be ok. I'm not going to be able to log data: because I switched to a Mac years ago, I'm using an old Windows laptop that needs to stay plugged in to the wall, as it's 10yr old battery is toast, so it can't come with me...

I was playing with the amp settings, and found that I could keep the motor amps at a full 600, but limit the battery amps and get the same speed and power. In my street mode I've cut the battery amps to 450, and in golf mode 350. I have no idea what this means, but my guess and hope is that it is working the battery's a little less hard? It seems to be running cooler...

Top speed downhill is a little better than 42mph. On flat it will get up to 40. I've got the throttle setting at 100% in both modes...

On the battery front, I'm not getting anything close to the range I need. I took it on an errand yesterday, I'm guessing about 3 miles each way, with a couple hours rest between. I was running nearly full out the whole drive. By the time I got home the cart was starting to slow and the voltage meter was all the way down to 46.01v when I got it in the garage. After resting for 10min, the meter read 48.8v. when I put it on the charger. The motor was only at 140*F, so that is comforting.

Obviously I am pulling a ton of amps to cruise at high speed for such long stretches. With new Trojan lead acids running down so quickly, now I'm afraid that even the 140ah lithium pack from HPEVS will not be enough to meet my challenge of driving 6 miles to the course, playing, and then driving home. -but then again, I have little idea what I'm talking about... This has me now looking into building a 200ah battery with CALB CA100 batteries I would be purchasing through Alibaba and getting shipped to me direct from China; they have a max peak amp draw of 1000, with a constant number around 600, and are rated 100ah each; I'd run parallel packs... Alternatively I'm thinking of doing a 21 cell leaf pack (3 parallel packs, rather than the typical 2) with those $50 cells bronsonj pointed out somewhere; I'm just not sure if they would fit in the cart... -still buried in research on the battery side of things; any advice is greatly appreciated! -I could go really crazy and build 2 packs of CALB 180ah cells in parallel, but those are $110 each, so "over budget" would be a vast understatement...

[Tsteak]

The Cart has been a success.

Just a followup/wrap-up incase anyone cares and because I've been dark for so long...

I haven't gone back through the thread, so some of this might be redundant.

I was able to solve the heat issues by building a new cable set out of 1/0 Gauge welding wire, and eliminating the 400amp fuse I had been using on my lead acid batteries. I think the fuse was severely limiting the flow of juice, and with the ZEVA bms installed it seems redundant. I also installed a couple blowers meant for a boat's engine compartment; one blows fresh air at the motor, and another exhausts air out from the top of the motor area and down to the road under the golf bags. I switch these on during the commute, when I'm running nearly full-out for up to 10minutes straight if I hit the lights right. My total commute is 15min, where it takes 20 in the car because I have to go around the course to the entrance...

The 21 Cell battery has been a success, I am able to drive 6 miles to the course, play 18 holes, and drive home. However, the ride home finishes with about 2 miles uphill, and I barely make it due to a couple cells that get too low before the others. Probably should have sprung for the newer leaf cells, not sure if that would make a difference... I plug the cart in at the course immediately after the round while we eat, and pay up, etc. and get home no problem. If I play in the morning, I can get enough charge during lunch to go another 18, but then will need to hang out for an hour or so after that to get me home without issue. I keep an extension cord in the cart.

I changed the gearing to 8:1, and with 600amps the cart still beats cars out of a red light, and now tops out at a cruising speed of 44mph in "street" mode. Surprisingly, this is not that scary. Obviously, it is not that smart... My top speed, "downhill with the wind behind me," was 49mph; this was down a short hill and was accidental and absolutely terrifying.

I am running 14" wheels with low profile tires, which I credit for the stability at high speed, and a set of Jakes disc brakes on the front wheels. Without the disc brakes, the cart is way too fast to call even remotely safe; the brakes work well and the cart stops reasonably from speed.

I have an audio system on the cart, and made it loud for the commute at speed. I threw a small amp in there and some JBL 6.5" speakers, and JBL makes an awesome powered sub that is meant to fit under a car seat; it fills out the lows nicely...

I still have to get the upholstery done, and will try to find time to post some pics...


Thanks all for your help along the way!

[JohnnieB]

Pictures please.

[Tsteak]

Well, despite going dark for over a year, the 45mph cart has not killed me yet!

I'm finally trying to get some photos in here, if anyone is still interested. These are before the leaf battery upgrade, and unfortunately the only decent pictures I have of the whole cart. I'm not sure if I'm attaching them correctly, my tech skills are truly retarding with age.

-Just previewed, sorry for the sideways pics, would appreciate a tip on that if anyone knows...

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It has been out of commission for the last several months; what started as body work and paint, turned into a full blown rebuild. I got into it, and just kept going, I couldn't help it... Converting to an A/C drive system, with Curtis controller, and HPEVS motor. With my gearing in the back end, it should be way too fast; I will limit it to a safe number, and hope that I don't try and see what "top end" is...

For the body work, I took the body completely off, and went nuts... I was always frustrated with the aluminum canopy struts, and so I welded a one-piece steel frame that got powder coated and will be much more solid and stable. With the body off, the battery compartment got sheet metal sides and floor welded in to create a sealed box so the road dust won't cover everything, as it had before. I've installed 2 runs of 1¼" electrical conduit from the battery compartment to the dash, to keep the audio wires and electrical separate; I was getting some feed back before.

I also re-worked the headlight situation. Anyone who knows an early Western 400, will remember the hood created "eyelids" over the headlights, which made them a little dangerous in a cart that does more than 40. I tossed their design and came up with my own, I have taken pictures this time and plan to actually post them... I'm not sure anyone is that interested in all that, but you might find some of it cool. I also found a couple pics of the leaf build, which I will include in the future...

I will be sending it off to the upholsterer when finished for a serious seat upgrade, and going to put a liner in the canopy as well...

All fiberglass body work and fill is now finished, and it's currently awaiting a final coat of primer and then will be painted, and finally assembled.

Hopefully I stay true to my intensions and keep you all posted, this should be a pretty epic cart when finally finished...

[wamcneil]

Very nice!