How much can my cart pull?

[scottyb]

A manufacture's engineer said I could not extend the lead with adversely effecting the accuracy. The gauge was calibrated for the amount of resistance in a specific length of wire. Nothing wrong with a gauge mounted near the motor - you only need to see it once in a while to know what's going on.

[Fegarex]

I bought 2 of them so I could extend one and leave another alone to compare. If it doesn't change I would like a dash mounted.

[JohnnieB]

The temperature sensor is a NTC (Negative Temperature Coefficient) Thremistor, so the resistance decreases as temperature increases. Adding longer wires will increase the total resistance, so the meter will indicate a lower temperature. How much lower is unknown, but thicker the wires used to extend the sensor, the less it will be.

So the company representative Scotty spoke to was correct technically, but might have been crying wolf a little bit in the practical sense.

Looks like the thermistor used has 10kΩ at 25°C and 338Ω less at 30°C, while it drops about 135Ω between 95°C and 100°C. (Not anywhere near as linear as YSI-400 thermistors used for patient monitoring back in the analog medical equipment days)

AWG 18 copper wire has 0.006385Ω/foot and there are two wires, so 0.01277Ω is added per foot of extension. Therefore a 10' extension would increase the total resistance by 0.1277Ω, so the meter will read about 0.04% low at room temperature and about 0.09% low near the boiling point of water.

In other words, the thing might stay within the +/-0.5°C specs with a 10' extension. Of course there will be some connections that'll add the total resistance, but my guesstimate is that it'll still read with a °C or two of the unmodified one with both probes submerged in an ice bath.

Let us know how close they read if you do extend the lead on one of the two you bought.

[Fegarex]

I didn't unwrap the other gauge but I have another similar digital gauge on the machine for outside temp and I brought down a household style digital thermos as well. Before modification the gauge read about 3 degrees lower than the other 2. After I added about 7 feet of 18ga. wire is still read about 3 degrees lower. That's close enough for what I want. I "put around" a lot and I know that can heat a motor about as much as anything. I've upgraded most things but the motor and voltage so the motor is going to be my weak link. Being able to monitor it will be nice! I so glad this forum is here so I know "what" is a hot temp.

[mark38090]

I have a 36v EZGO TXT, other than the "speed/tow" switch add far as I know the electronics are all stock. I have 22x10x10 DOT tires and a 6 inch lift and ff every week i pull a trailer around the prison where i work that is easily 1200 pounds. 90% of that is on pavement but I've never had an issue. There's very little resistance while rolling with the exception of one particular long stretch that climbs a hill over the length of a mile but my cart is a workhorse.