Electronics > Power/Renewable Energy/EV's
EV charging - More efficient at higher (48) or lower (32) amperage with L2?
Siwastaja:
--- Quote from: tom66 on November 25, 2023, 03:32:42 pm ---Most electric cars use around 150-300W to run the charging systems. This provides power for the BMS, coolant pumps, contactors, computers and whatever else needs to run to support the charging. If it's very hot outside, they might need to provide additional fan or air-conditioning cooling circuits. If it's very cold, they might need to run a battery heater.
--- End quote ---
Yeah. You can, possibly significantly, reduce the energy consumption caused by this constant load part by simply stopping charging a bit earlier, like at 98% SoC, to avoid ramp-down of charging current in CV phase/balancing. But every car is different. It seems my 62kWh Nissan Leaf takes around two hours to finish from the start of current ramp down, and while I'm sure it doesn't waste the higher end (300W) of your numbers while in CV/balancing, it's still surely tens of watts which do not end up in the battery pack, if from nothing else, but from fact that the charger power electronics are likely not designed to be efficient over such wide power range. OTOH, Nissan Leaf is quite simplistic in design, does not use coolant pumps, and any "computers" that run are not anywhere near the numbers Tesla probably still uses (although I guess the days of always-on 200W phantom consumption caused by six general purpose computers running Ubuntu are long over).
tom66:
--- Quote from: Siwastaja on November 25, 2023, 04:39:40 pm ---
--- Quote from: tom66 on November 25, 2023, 03:32:42 pm ---Most electric cars use around 150-300W to run the charging systems. This provides power for the BMS, coolant pumps, contactors, computers and whatever else needs to run to support the charging. If it's very hot outside, they might need to provide additional fan or air-conditioning cooling circuits. If it's very cold, they might need to run a battery heater.
--- End quote ---
Yeah. You can, possibly significantly, reduce the energy consumption caused by this constant load part by simply stopping charging a bit earlier, like at 98% SoC, to avoid ramp-down of charging current in CV phase/balancing. But every car is different. It seems my 62kWh Nissan Leaf takes around two hours to finish from the start of current ramp down, and while I'm sure it doesn't waste the higher end (300W) of your numbers while in CV/balancing, it's still surely tens of watts which do not end up in the battery pack, if from nothing else, but from fact that the charger power electronics are likely not designed to be efficient over such wide power range. OTOH, Nissan Leaf is quite simplistic in design, does not use coolant pumps, and any "computers" that run are not anywhere near the numbers Tesla probably still uses (although I guess the days of always-on 200W phantom consumption caused by six general purpose computers running Ubuntu are long over).
--- End quote ---
You would be surprised at how much does get wasted. I've checked my ID.3 and when in charge mode, the DC-DC current measured at around 10 amps. That's at least 130 watts. At 7200 watts of charging power, that's around 2% loss in support systems. (The DC-DC isn't 100% efficient either, but this is probably negligible extra loss.)
Balancing depends a lot on the car too. Hyundai vehicles tend to balance around 60-70% SoC, and will continue that process throughout charging. Not sure about my ID.3, but it's usually linear in charge rate - adding 1% takes just as long at 10% as it does at 95%. It charges at the full 7kW up until the battery is full. Perhaps this is because the battery is not actually full at 100% SoC, but around 90-95%, as regen is still possible at around 30kW when the battery is at 100%.
One of the issues with EVs built by legacy automakers is that they are still built a bit like petrol cars. With a petrol car there hasn't been a particular obsession over 12V losses because whilst it does increase fuel usage it was a small line item in overall losses. For instance my old Golf GTE kept the electric power steering controller energised while charging... Why? Because it is on the same bus as the ECU which talked to the BMS and charger, and it was presumably simpler to do that. Little decisions like that have a big impact.
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