Warm wires

[Naturile]

I was riding my cart today half speed, ezgo txt 1 year old us batteries Scotty battery cables plum quick motor heavy duty f/r switch from Scotty 36 volts . It just quit moving got off the wires from the f/r we're warm not hot let it sit for 15 minutes got on it and now works fine????? What do you think is the problem?

[Revolution]

Was the controller hot also? You might try cleaning all of your cables if they are not spotless. But take some voltage readings of the pack the next time you drive it.

[Naturile]

Nope only the wires from the f/r switch everything else was fine, but I know riding at half throttle is hard on them

[JohnnieB]

Sounds like the controller went into over-temp shutdown.

What controller are you running?

The controller temperature is typically sensed on the bus bar the MOSFETs are attached to (M-), so the controller case could feel relatively cool when an over-temp condition existed at the M- bus.

Scotty makes some exceptionally good cables, but like all cables with copper conductors, if you run a lot of amps through them, they will warm up some and 4Ga cable will warm more the 2Ga cables at the same amp flow.

If you are running tires taller than 18" plus a high speed motor, the amp draw can be mighty high when driving at low speeds.

[Naturile]

20 inch tires 400 amp curtis

[DaveTM]

No smell of "rubber" (aka wire coating) burning?

[Naturile]

No nothing got that hot the wires were just warm, only 2 wires from the f/r switch! I rode it today it was fine but not slow like yesterday. I just don't like. It knowing when and if it will do it again

[JohnnieB]

Unless they are low pressure type (<10 PSI max inflation pressure), 20" tires aren't big amp hogs, so a 400A controller (Curtis 1204?) ought to be okay.

In a series drive, the same amount of current (in fact, the same current) flows through all 13 high current cables, so all 13 ought to run at about the same temperature. (The longer cable may run slightly warmer - they have more resistance since they are longer.)

If some are getting significantly warmer that the others, verify the connections are clean and properly tightened. Battery studs are only about 8.5 ft/lb, but I don't know the torque specs for the F/R switch and motor, so look them up.

I've yet to find any specs on how much cable warming is acceptable, but my guess is about 10°F above ambient air temperature is normal.

------
Is there a thermal pad or thermal grease between the controller and heatsink? If not, it might be a good idea to remount it, using thermal grease.

[Volt_Ampere]

Longer cables also have more length and surface area to cool so they should not really run hotter. The place most folks get into trouble is at the connections. Either where the wire is crimped to the connector or at the bolted connection itself. These must be very clean and secure. Warm wires won't hurt anything if they are really warm. (No pain when you hold onto them.)

[scottyb]

In my HD F&R heat tests temps at Solenoid and F&R terminals ran into the 130º range without component damage with aftermarket motors on long steep inclines. This feels pretty warm to touch.