I've noticed this issue since day one of purchasing the Kona several months ago but am ready to investigate it now at a technical level and would like to hear from those owners who are lucky enough to have 32 amps at home, or otherwise fully utilise the OBC's capacity. I'm in NZ and it's been summer-like weather the entire 4 months I've owned the car. I thought this might also be relevant as the northern hemisphere moves into summer.
In summary, the OBC drops the charge power in numerous steps all the way down to 0.5 kW (then cycles up and down) after roughly an hour at 7.4 kW, 32 amps (on a 43 kW ABB EVSE.) This happens at all state-of-charge levels that I typically find myself at, between 50 and 90%. I often charge only for an hour at a time anyway (public charger near home) so it doesn't often affect me but now that it's quite warm it can be an issue in less than an hour, or if I return later for a second short session. This is the only 32+ amp Type 2 station I have good access to and that cable is rarely used by other EVs but seems to be in top working order. I can't easily test this issue on other EVSEs.
Taking temperatures around the front bay in an ambient of 25-28°C gives me 52°C on the top surface of the OBC, the fan is not running and if the water pump is running it's too quiet to hear. The hoses to the radiator are 45 and 40°C. Nothing seems abnormal but why would it throttle itself? What temperature gradient might there be between the power semiconductors and the coolant and why would the fan not start if heat was the issue? I doubt that would be more than 20 C; 75 C at the devices should be fine.
Based on a diagram of the cooling and HVAC system, the OBC is plumbed in series with the motor, drive electronics (which of course provides thermal mass,) water pump and radiator.
Yesterday I had an idea to run the heater during this adverse event, as it would use the heat pump and pull cold air through the evaporator and radiator. That didn't work because the max heater setting is 27, below the ambient.
So I tried the AC, which did run the fan but nothing obvious changed, noting of course that using AC means hot air is being pulled through the radiator, not what I want. Using a fan or spraying water over the radiator is not practical, people would gather around and ask silly questions
Generally if I restart the charging session the power will go back to 7.4 kW for perhaps 10 minutes before dithering down to 6.0, 3.8, 1.8, 0.5 over some minutes, then cycling up and down again.
I'm of the opinion that the OBC should be able to operate continuously and there is no reason why the it should back off regarding the Kona's battery in the ambient and SoC conditions I'm in. The EVSE is offering 63 amps and has no reason to limit that. If the OBC is overheating then the fan and pump should be working to prevent that before power throttling starts.
A message to Hyundai NZ did not unearth an explanation, responding: "It doesn't seem if anything is out of the ordinary but please keep us posted with your monitoring."
I'm not going to try the dealer unless there is evidence that my car is faulty.
One owner in the UK has offered info on FB that his has charged fine for a number of hours, but in 7°C ambient.
So, owners using full Type 2, are you able to charge for hours at a time under full power, and what is your ambient temp? To be clear, fast DC charging works fine and I can use it ... this is the AC side only in question.
In summary, the OBC drops the charge power in numerous steps all the way down to 0.5 kW (then cycles up and down) after roughly an hour at 7.4 kW, 32 amps (on a 43 kW ABB EVSE.) This happens at all state-of-charge levels that I typically find myself at, between 50 and 90%. I often charge only for an hour at a time anyway (public charger near home) so it doesn't often affect me but now that it's quite warm it can be an issue in less than an hour, or if I return later for a second short session. This is the only 32+ amp Type 2 station I have good access to and that cable is rarely used by other EVs but seems to be in top working order. I can't easily test this issue on other EVSEs.
Taking temperatures around the front bay in an ambient of 25-28°C gives me 52°C on the top surface of the OBC, the fan is not running and if the water pump is running it's too quiet to hear. The hoses to the radiator are 45 and 40°C. Nothing seems abnormal but why would it throttle itself? What temperature gradient might there be between the power semiconductors and the coolant and why would the fan not start if heat was the issue? I doubt that would be more than 20 C; 75 C at the devices should be fine.
Based on a diagram of the cooling and HVAC system, the OBC is plumbed in series with the motor, drive electronics (which of course provides thermal mass,) water pump and radiator.
Yesterday I had an idea to run the heater during this adverse event, as it would use the heat pump and pull cold air through the evaporator and radiator. That didn't work because the max heater setting is 27, below the ambient.
So I tried the AC, which did run the fan but nothing obvious changed, noting of course that using AC means hot air is being pulled through the radiator, not what I want. Using a fan or spraying water over the radiator is not practical, people would gather around and ask silly questions
Generally if I restart the charging session the power will go back to 7.4 kW for perhaps 10 minutes before dithering down to 6.0, 3.8, 1.8, 0.5 over some minutes, then cycling up and down again.
I'm of the opinion that the OBC should be able to operate continuously and there is no reason why the it should back off regarding the Kona's battery in the ambient and SoC conditions I'm in. The EVSE is offering 63 amps and has no reason to limit that. If the OBC is overheating then the fan and pump should be working to prevent that before power throttling starts.
A message to Hyundai NZ did not unearth an explanation, responding: "It doesn't seem if anything is out of the ordinary but please keep us posted with your monitoring."
I'm not going to try the dealer unless there is evidence that my car is faulty.
One owner in the UK has offered info on FB that his has charged fine for a number of hours, but in 7°C ambient.
So, owners using full Type 2, are you able to charge for hours at a time under full power, and what is your ambient temp? To be clear, fast DC charging works fine and I can use it ... this is the AC side only in question.