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Temperature Throttling Thresholds
OpenEVSE Support
Attached is a temperature rise graph at different current settings. The station is a stock v5 kit with a OpenEVSE NEMA 14-50 input cable and 40A J1772 cable. The blue line is the ambient temperature and red is the internal temperature. Grey is the output power.
The Temperature rise over the starting temperature for this configuration should be about:
Idle - about 2 - 3C (over ambient)
Charging 6A - 5C
Charging 12A - 6.5C
Charging 18A - 10C
Charging 24A - 13.5C
Charging 30A - 18.2C
Charging 40A - 26.7C (not pictured on this chart)
@Keith it looks like your rise is about 29C over the starting temperature. What is your configuration for the high current path (input cable, relay, EV Cable)?
Today I did have an event triggered by the openEVSE charging at 32A and the internal temperature climbed to 65F. The pilot signal dropped by half to 16A and after cooling the pilot signal returned to 32A. Another 65F trip sent the current back to 16A and after a 5 min cooling the pilot signal returned to 32A where it remained for the remainder of the 50KWHr charge cycle. A couple of weeks ago I opened the box and tightened the high current fasteners and looking for any high resistant clues but couldn't find any suspects. I'm thinking I need to use a thermal imaging device to troubleshoot the temperature source .
OpenEVSE Support
The pilot signal defines the maximum available. The vehicle may draw any current up to but not exceeding the pilot. It sounds like the reduction was triggered by the EV.
OpenEVSE Support
What version of firmware are you running? Early versions of firmware had much more aggressive throttling. Watching the pilot is a good way to know the event originates from the station. If you upgrade to the latest firmware, temperature throttling information will stay on the display until the EV is unplugged.
I'm getting throttling at 54C but not sure if it's triggered by temperature or by the EV. How do you determine if it is a temperature event? I'm thinking a plot of the pilot signal will show this. The EV will limit the current with a low voltage event while the pilot remains at set value but a temperature throttle will reduce the pilot signal.
OpenEVSE Support
Great, I think the new values will improve the charging experience while still maintaining the added safety of throttling.
Craig Kirkpatrick
Compelling evidence that higher temperature thresholds are safe with the OpenEVSE controller. I'll make the changes before Monday most likely.
Chris Howell
I have been testing increased Temperature thresholds for a few months, I added 10C to each setting. I would like to purpose setting the default throttling to start at 62C. This plus the option to disable in the latest development releases would provide a better experience and still provide the safety of shutdown during abnormal events. And allow the user to disable when charging can be monitored.
Here is 5 days of data charging at 40A. Daily temperatures for the period were 100F. I did experience throttling to 50% on the first and last day, but I think that it was the appropriate time to limit. Fully charging was achieved both days. Charging at 32A or less has not caused any throttling even on days that were 110+.