Level 2 Charging rate
- Thread starter kenneymac
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jadnashuanh
Well-known member
FWIW, the charging rate is first bounded by the device involved and second, by what the vehicle wants or can accept at the time. To explain, the EVSEs are designed for some maximum amperage. They output a signal that tells the car how much that is so that the car will not try to draw too much, and overload the supply circuit. But, power = volts * amps, and the supply voltage is not always consistent. With a few exceptions, the i3 can accept a maximum of 7400W. Solving that with the limitation of say that 30A, would mean 7400/30=246.67vac input. If you have, say 220vac input, limited to 30A, that would be 220*30 = 6,600W. FWIW, in the USA, a common commercial power level is 208vac, so that 30A device would only provide 208*30=6,240W. Generally, the grid is regulated to provide +/- 10%, so that would adjust the power levels accordingly. In extreme conditions, it can vary more.
If the signal output from the EVSE is off a little, it may be telling the vehicle it has say 29A available, which would limit the amount even more. If the car's response to that was not calibrated, it may not try to draw as much as was available. Ideally, the EVSE would have more power available that the vehicle can accept, then it would always maximize the charging rate, but practical conditions to not always allow that. While my EVSE is limited to 30A (a more common level today is 32A max), because my typical input voltage is fairly high, I usually can max out the i3's capabilities, but even it I couldn't, generally, I've got overnight before I need full charge again.
What might be annoying is if the unit has a charge based on time verses Kw delivered...you'd want it to always max out the vehicle.
Then, the car won't allow that maximum rate all the way up until it is full, or even at the beginning, if the battery pack is either too cold or too hot. It will taper up to the maximum (assuming it needs enough juice), and then taper down as it approaches full.
If the device is announcing an average, verses instantaneous, that can be an issue to, as your peak would likely be much higher.
If the signal output from the EVSE is off a little, it may be telling the vehicle it has say 29A available, which would limit the amount even more. If the car's response to that was not calibrated, it may not try to draw as much as was available. Ideally, the EVSE would have more power available that the vehicle can accept, then it would always maximize the charging rate, but practical conditions to not always allow that. While my EVSE is limited to 30A (a more common level today is 32A max), because my typical input voltage is fairly high, I usually can max out the i3's capabilities, but even it I couldn't, generally, I've got overnight before I need full charge again.
What might be annoying is if the unit has a charge based on time verses Kw delivered...you'd want it to always max out the vehicle.
Then, the car won't allow that maximum rate all the way up until it is full, or even at the beginning, if the battery pack is either too cold or too hot. It will taper up to the maximum (assuming it needs enough juice), and then taper down as it approaches full.
If the device is announcing an average, verses instantaneous, that can be an issue to, as your peak would likely be much higher.
graememwl
Well-known member
kenneymac said:
Although the ChargePoint L2 chargers I use are rated for 6.6kW, I have never seen them report more than 6kW while charging.
jadnashuanh
Well-known member
The i3 may have better battery management logic and, at the time and conditions available, is limiting the maximum available to preserve the batteries. Again, are you talking average or peak?
Where I live, I can usually see a higher rate in the winter than the summer because the input voltage tends to be lower in the summer. Remember, the power = volts * amps, and if the voltage changes, the power delivered does too. What would be more telling is to be able to monitor the amps flowing. I wired a meter to mine and can monitor both voltage and amperage (it calculates delivered watts). With my 30A EVSE, I've seen it at like 29.8A or so, so pretty close to that theoretical maximum of my EVSE.
Where I live, I can usually see a higher rate in the winter than the summer because the input voltage tends to be lower in the summer. Remember, the power = volts * amps, and if the voltage changes, the power delivered does too. What would be more telling is to be able to monitor the amps flowing. I wired a meter to mine and can monitor both voltage and amperage (it calculates delivered watts). With my 30A EVSE, I've seen it at like 29.8A or so, so pretty close to that theoretical maximum of my EVSE.
I think the i3 does probably have a better battery management system, so i think something else in the car is starting to fail.
Everyone always talks about external issues, but I live in Los Angeles and the weather here would be optimal for charging. The next thing is power from the charger. I'm charging at a commercial charger at work and have spoke to chargepoint, they had told me that I'm charging at a lower rater than other cars that have been charging through the day. At this point I think there is either a software limitation in the car or the health of the batteries is in question. Would anyone know what component should be checked and how? Per BMW they have not found any faults in the system. I'd like to have this fixed before my new car warranty has expired as the batteries itself has a 8 year 100k warranty I've been told that the charging components are not.
Everyone always talks about external issues, but I live in Los Angeles and the weather here would be optimal for charging. The next thing is power from the charger. I'm charging at a commercial charger at work and have spoke to chargepoint, they had told me that I'm charging at a lower rater than other cars that have been charging through the day. At this point I think there is either a software limitation in the car or the health of the batteries is in question. Would anyone know what component should be checked and how? Per BMW they have not found any faults in the system. I'd like to have this fixed before my new car warranty has expired as the batteries itself has a 8 year 100k warranty I've been told that the charging components are not.
alohart
Well-known member
That would be kW (power), not kWh (energy).kenneymac said:
Most 2014 i3's had a defective KLE (comfort charging electronics) that could fail when outputting its full 3.7 kW charging power (a second module outputs an additional 3.7 kW). So BMW installed system software that limited the KLE's maximum charging power to ~1.8 kW, or 3.7 + 1.8 = 5.5 kW maximum charging power, to minimize the risk of the KLE failing which would reduce the maximum charging power to 3.7 kW. When a redesigned KLE was installed under warranty, the system software also updated to restore the full 7.4 kW of charging power.
Even if you have a 2014 i3, it seems unlikely that the original KLE would not have been replaced and the system software updated. But if you have a 2014 i3, this might be something to check.
