In this article I’ll show you how easy it’s to estimate the on-board charger efficiency of an electric car by using WLTP ratings.
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I’ll use WLTP ratings in this article, but you can also use EPA or NEDC ratings, since they also measure plug-to-wheels consumption, this means that they include charging losses.
It’s important to notice that for measuring the consumption the charging was made by using a domestic socket at low current (10 A) and some on-board chargers are not very efficient at low currents.
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Let’s start with some of Europe’s most popular electric cars.
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Renault ZOE
- Range: 395 km
- Consumption: 17,2 kWh/100 km (with charging loses)
- Usable battery capacity: 52 kWh
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First we start by calculating the consumption without charging loses.
395 km - 52 kWh
100 km - X
X = 52 x 100 ÷ 395 = 13,164556962 kWh/100 km
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Now if we divide that number with 17,2 kWh/100 km we’ll get the on-board charger efficiency.
Y = 13,164556962 ÷ 17,2 = 0,765381218722 = 77 %
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It’s no secret that Renault’s Chameleon on-board charger is not very efficient at low currents. However, Renault does seem to have made its on-board charger more efficient in the new generation of the ZOE. Previously, the charging efficiency of the R90 models at 10 A was estimated at 71 %.
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Now that you know the steps required to calculate the efficiency of an on-board charger, in next examples I’ll just show you the final results.
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Renault Twingo ZE
- Range: 190 km
- Consumption: 16 kWh/100 km (with charging loses) -Â 11,2 kWh/100 km (without charging loses)
- Usable battery capacity: 21,3 kWh
- On-board charger efficiency: 70 %
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Dacia Spring Electric
- Range: 225 km
- Consumption: 14 kWh/100 km (with charging loses) - 11,9 kWh/100 km (without charging loses)
- Usable battery capacity: 26,8 kWh
- On-board charger efficiency: 85 %
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Volkswagen ID.3 Pro S
- Range: 549 km
- Consumption: 15,9 kWh/100 km (with charging loses) - 14 kWh/100 km (without charging loses)
- Usable battery capacity: 77 kWh
- On-board charger efficiency: 88 %
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Volkswagen e-up
- Range: 260 km
- Consumption: 14,4 kWh/100 km (with charging loses)Â - 12,4 kWh/100 km (without charging loses)
- Usable battery capacity: 32,3 kWh
- On-board charger efficiency: 86 %
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Peugeot e-208
- Range: 340 km
- Consumption: 17,6 kWh/100 km (with charging loses)Â - 13,5 kWh/100 km (without charging loses)
- Usable battery capacity: 46 kWh
- On-board charger efficiency: 77 %
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Nissan LEAF
- Range: 270 km
- Consumption: 17,1 kWh/100 km (with charging loses)Â - 13,3 kWh/100 km (without charging loses)
- Usable battery capacity: 36 kWh
- On-board charger efficiency: 78 %
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Kia e-Soul
- Range: 452 km
- Consumption: 15,7 kWh/100 km (with charging loses)Â - 14,2 kWh/100 km (without charging loses)
- Usable battery capacity: 64 kWh
- On-board charger efficiency: 90 %
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Kia e-Niro
- Range: 455 km
- Consumption: 15,9 kWh/100 km (with charging loses)Â - 14,1 kWh/100 km (without charging loses)
- Usable battery capacity: 64 kWh
- On-board charger efficiency: 88 %
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Previously the Kia e-Niro was homologated with a WLTP range of 485 km, but Kia revised the rating in December 2018 and dropped it to 455 km. This change makes the on-charger efficiency estimation less reliable, because the e-Soul and e-Niro should have the same on-board charger, but we get different estimations.
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Hyundai Kona Electric
- Range: 482 km
- Consumption: 14,7 kWh/100 km (with charging loses)Â - 13,3 kWh/100 km (without charging loses)
- Usable battery capacity: 64 kWh
- On-board charger efficiency: 90 %
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Hyundai IONIQ Electric
- Range: 311 km
- Consumption: 13,8 kWh/100 km (with charging loses)Â - 12,3 kWh/100 km (without charging loses)
- Usable battery capacity: 38,3 kWh
- On-board charger efficiency: 89 %
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Tesla Model 3 LR
- Range: 580 km
- Consumption: 16 kWh/100 km (with charging loses)Â - 12,6 kWh/100 km (without charging loses)
- Usable battery capacity: 73 kWh
- On-board charger efficiency: 79 %
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Summing up…
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On-board charger efficiency estimations
- Hyundai Kona Electric: 90 %
- Kia e-Soul: 90 %
- Hyundai IONIQ Electric: 89 %
- Kia e-Niro: 88 %
- Volkswagen ID.3 Pro S: 88 %
- Volkswagen e-up: 86 %
- Dacia Spring Electric: 85 %
- Tesla Model 3 LR: 79 %
- Nissan LEAF: 78 %
- Peugeot e-208: 77 %
- Renault ZOE: 77 %
- Renault Twingo ZE: 70 %
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Anyway, remember that these estimations are for worst-case scenarios, by charging with domestic sockets at low current (10 A). If you charge at higher currents you can achieve better efficiency figures, especially if your electric car is a Renault.
If you can charge your electric car at 32 A, do it. Nowadays, a good portable EVSE with adjustable current is not that expensive.
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Lastly, if you want to do your own calculations but can’t find some variables, let me know.