Motor heat

Conradconrad

Cart runs great. Apologize in advance for the length of the post

Concern I have is, the N.O. thermostat(which trips at 140*C) as a high temperature warning has been set off several now with various distance drives.

Twice was about 7 & 7.5 miles worth of street driving, all flat roads, just four way stops( maybe 12 of them) and maybe 5-6 large speed bumps that you have to slow down to 5-10 mph to go over them. I did a third test, about 3 miles one way( similar road ways), Then a stop for about 20 minutes and then 3.5 miles back (on the same roadways just different route) thermostat still tripped for too much heat.

I also have a temperature probe attached to the motor case with JB weld. Temperature measured about 160-165*F at the motor case each time this occurred. I verified with a laser temp gun and temperature was within a few degrees. Once the thermostat trips, it powers a buzzer to beep and flash(thats how I decided to connect it) it takes about 17-18 minutes for the buzzer to turn off. During that time the first 5-6 minutes temperature always rises, the remaining 12-13 minutes temperatures lower from 160ish *F to about 145*F.

Fourth test I did the other day was on a straightaway, all flat with only two four way stops, full throttle the entire time, I was about to reach about 8.5 miles before the thermostat closed. Same cool off as described above

I'm trying to understand how this all works. I recall from various readings online that duty that is more consistent does not increase temperatures at the internal/brushes as quickly. I'm interested in how quick the internals of the motor reduce in temperature as the motor casing seems to be a heat sink? Is there less heat at the brushes when motor is at max rpm since its pulling less amps vs keeping the motor spinning at 50-70% of max rpm?

Also I'm thinking I can change the throttle maps for a calmer acceleration since I have so many stop and go's would that decrease temps? Im currently utilizing the alltrax stock throttle map it came with

Im trying to understand the relationships and patterns that way, my route choices and driving style- the only deltas, can be accommodated accordingly.

Goal Im trying to accomplish is to make it to about 10-11 miles without hitting high temperatures. Not sure if this is even possible. Maybe with a stop halfway to let temperatures drop? All this is intriguing as my area has several stock carts that had back seat put on them and are being used as beach taxis with lots of stop and go, constant usage with 4 passengers all day long. Maybe I need to send to PQ to get some motor case vents?

BGW

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bronsonj

Are your brakes dragging? That would increase load which would mean higher amp draw and higher temps. More amps = higher temps (generally).

You are correct, running a full speed should reduce the amp draw and reduce the temp rise.

In addition to brake drag, check your front end alignment. Should be toed in about 1/8 to 1/4 inch IIRC.

scottyb

You did a good job of gathering and presenting info. What motor and controller are you running?

Conradconrad

Brakes dragging to my knowledge- No as I checked several months ago. However I'm going to recheck them again to be sure since I don't like to assume things. Alignment- that could be possible, I will need to check. I am inexperienced as far as alignment is concerned so will take some reading up in the ezgo manuals and possibly another thread for help lol.

Curious, those seem like great suggestions and I'm sure common issues. In addition to common issues, do you think I'm heating up quicker than what would be expected?

Conradconrad

Thanks! I'm learning !

Alltrax xct 500, 42v, 2 gauge wires, stock gears. Street thread tires that measure just over 17.5 inches. Backseat, no lift. All street legal- on road use only, all flat/hot Florida roads.

EMP motor- it's an upgraded D&D motor 170-505-0001
This motor - the brush cross section is 25% larger than in stock motor in addition to being heavy duty type. The motor has high speed banding. The motor also has a slightly longer stack which should be helpful with acceleration.

Thanks guys

JohnnieB

True for Series motors, but not true for SepEx motors.

To get max RPM from a sepex motor the field current is at a minimum and the motor's efficiency is greatly reduced, so motor is converting a higher portion of the armature amps to heat and the motor runs hotter at max RPM than it does at something less than max RPM. The coolest running speed for a sepex drive cart is the fastest speed with the least armature amps.

On a dynamometer, my sepex motor has an efficiency range of 66% to 83% depending on RPM and Field amps. In the cart, my motor runs the coolest at about 89% of max speed, which is 25MPH vs the 28MPH max.

Of course, that is my specific motor in my specific cart, other sepex motors in other carts with different field maps will be different.

JohnnieB

Since the case temperature peaks at about 165°F, I suspect the N.O. 140°C (284°F) thermostat is faulty, but I could be wrong.

I'd contact Chuck at EMP and get his input.

JohnnieB

Also, record some data logs and when the over-temp alarm goes off, stop cart, put f/r in neutral and shut key off. This will identify where the problem occurred in the log so the immediately preceding field amps, armature amps and RPM can be reviewed. Might give us a clue.

Conradconrad

Thank I am waiting on his response

Conradconrad

I will do that! When you state over-temp alarm- are you referring to my buzzer/thermostat ?

As far as logging data can I start logging when I know I am about 0.5-1 mile out from the thermostat tripping?