I have been noticing lately that the power output of my OpenEVSE 50A kit is inconsistent. I have a 2013 leaf which I have been charging with the OpenEVSE for about eight months. Up until a month ago the car would charge between 6,000 and 7,000 watts until it tapered off at the end. Now it seems there are three levels of charging. What could be causing this?
That is throttling due to exceeding temperature thresholds. If you are running firmware 3.7.8 (version is displayed when powered on) the thresholds are very conservative. Later releases increased the thresholds by 10C which will greatly reduce unnecessary throttling. If you are running a later version, you should inspect all the high current connections and ensure they are clean and secure.
I'm on version 3.10.3. The temperature ranges form 156F to 147F while charging and matches the current output graph. Once above 154F (67C) the power is dropped. My OpenEVSE is mounted on my garage wall so it is not affected by sunlight. Ambient air temp is about 80F. Does that sound out of the normal?
I will take a look at the high current connections.
That sounds a lot higher than normal. On my station in the Mojave desert, I charge at 40A while my garage has been above 100F all day. I can charge at 40A indefinitely without throttling. I would recommend inspecting the high current wiring at the contractor.
Well you were right. The car side high current lines were in very bad shape. I cut the bad part off and reconnected and the temperatures are back to normal. So how do I prevent this in the future?
There are a couple things you can do.
The build guide suggests stripping 3/4" - 1" of insulation, combining the 2 wires and folding in half (so the equivalent of 4 wires are in the lug). This gives more contact area,
Another option is to do the same, combine the 2 wires and fold in half with 6AWG ferrules, however this requires a crimper and a die.
Another thing you can do to receive the earliest possible warning is to set up an E-mail notification if temperature climbs above 65C or even 60C if you prefer to get the notification before the throttling kicks in.
details are in the guide here:
Step 6 Example 2.
Example 2 - Send E-mail every 5 minutes when temperature exceeds 65C. Add the values in the Blue box to the active Temp input. Logic If temperature is greater than 65C and 300 seconds have passed (5 minutes) Send an Email with the current temperature.