Tests carried out by our sister publication Auto Zeitung have shown that range and battery size aren’t the only considerations when it comes to buying an electric car. Assessing the accuracy of charging times and claimed charging potential across seven different electric vehicles (EVs), the test results are fascinating.
It’s natural for car journalists to interrogate the claims of manufacturers. The latter has a canny knack for painting the most positive picture of its latest model’s performance – even if those figures emerge from laboratory conditions and don’t reflect real-world performance. So, we often find ourselves eyeing stat sheets sceptically.
Since every one in six vehicles sold in the UK now is an EV, it’s right that the performance of the batteries and charging capabilities are scrutinised more closely. Especially with everyone asking that all-important ‘how much does it cost to charge an electric car‘ question. Though range is much discussed, and battery degradation is a genuine concern, wrapping one’s head around the physics of charging is a whole other ball game.
Is a higher-capacity battery better?
Though we look at battery capacity in more detail here, and charging in general here in these articles, we’re dealing specifically with charging potential and the accuracy of manufacturer claims.
Batteries are amazing things. A delightful mix of chemistry and physics is involved in propelling us with zero emissions. While higher-capacity batteries will offer more power output, that doesn’t necessarily mean there’s a correlated increase in potential mileage, or charging capacity.
kWh is the unit that denotes how big a battery is, kW tells us about power delivery. So Kia’s 77kWh battery would, in theory, take roughly 10 hours to charge on a 7.4kW home charger.
However, nothing is ever that straightforward, right? State of Charge (SoC) indicates the percentage of energy left in the battery. Charging between 10% SoC and 80% SoC is the safest window for charging. We explain more below.
The test conditions
Mimicking typically British temperatures on the pre-spring winter days, seven EVs were taken out in four to eight degrees Celsius, on a route incorporating city, country and motorway driving. The vehicles tested were: Renault Zoe E-Tech R135 ZE. 50, Vauxhall Corsa Electric, Volkswagen ID.4 Pro Performance, Polestar 2 Long Range Single Motor, Mercedes EQS 580 4Matic, Kia EV6 77 kWh AWD and Porsche Taycan 4S.
All vehicles were put in Eco mode, if possible, and the climate control was on too. Pushing the vehicles no further than a maximum 124mph, they arrived at the public rapid charger with just under 10% battery capacity. The route had provided some warm up, which is better for charging.
The headline findings:
- Mercedes, Polestar and Porsche pre-condition the battery
- The Kia EV6 battery also did well
- The Renault Zoe is a mighty little sport
- Mercedes EQS 580 4Matic exceeds manufacturer spec
- Volkwagen also outperformed manufacturer claims but the Vauxhall Corsa Electric fell short
- Polestar 2 teaches us to disconnect at 80%
- Porsche Taycan is the fastest charging EV on the market
Mercedes, Polestar and Porsche pre-condition the battery
In a feat of impressive battery anticipation, Mercedes, Polestar and Porsche have integrated the navigation with a battery pre-conditioning system. Thus, if you set the guidance to a selected charging point, the batteries will preheat the batteries to receive the charge.
With such exemplary battery management, the Polestar 2 Long Range Single Motor accepted a 144kW delivery after just two minutes. This then increased to the claimed 150kW after four minutes.
The Kia EV6 battery also did well
The Kia EV6 only took five minutes to condition the batteries, ready to receive a greater power delivery. The testers recorded an increase from 200kW to 230 kW after five minutes, then more after 10 minutes. What’s more remarkable is that the EV6 achieves this without a preconditioning feature.
The Renault Zoe is a mighty little sport
A stretch on the motorway was enough to warm the Renault Zoe up. Immediately after plugging in the CCS connector, the charging power jumped to 42kWh, of the claimed 50kWh. It remained here for 30 minutes before another brief power increase, then it decreased continuously.
The Zoe is one of two cars on the UK market that is configured to receive 22kW power delivery, so it wasn’t surprising that this battery is capable of taking on such a charge so quickly.
Mercedes EQS 580 4Matic exceeds manufacturer spec
The Mercedes EQS 580 4Matic bucks the usual trend of vehicles falling short of manufacturer claims. It charges faster than Daimler reckons by a full minute. Granted, that won’t make a dent in the real-world, but it’s one of the biggest batteries on the market too, at 107.8kWh. While a kerb weight of 2,585kg should have a negative effect on both performance and energy consumption, the EQS challenges such perceptions. It has the agility of a vehicle far lighter.
Volkwagen also outperformed manufacturer claims but the Vauxhall Corsa Electric fell short
The Volkswagen ID.4 should charge at a maximum rate of 125 kW, but the ID.4 even exceeds this value significantly in the first 10 minutes with 126 to 132 kW power delivery being recorded.
On the other hand, the Vauxhall Corsa-e proved to have a peak charge value of 91 kW, missing its 100 kW maximum potential. Range also seems to be in question; a 72.7 mile journey was recorded as 137 mile loss by the Corsa-e’s computer. Of course, motorway driving drains all electric vehicle batteries quickly, but it was notably rapid on the Corsa-e.
Polestar 2 teaches us to disconnect at 80%
As we mentioned in the introduction, charging between 10% and 80% State of Charge (SoC) is the best way to minimise degradation to the components of the battery. The charging time beyond 80% slows considerably to mitigate the production of heat energy, i.e. no one wants to fry their batteries. The Polestar 2 however demonstrated just how slow this can be. The 2’s 75 kWh battery only needs 36 minutes to charge from 10 to 80%. Yet, it takes a further 87 minutes to reach 100%.
Thus, if you disconnect the charger at 80% battery you’re not only making best use of your time, but you’re also extending your car’s battery life.
Porsche Taycan is the fastest charging EV on the market
Like the EV6, the Taycan 4S uses Hitachi-supplied 800V inverter, as part of its battery-based powertrain. This means 90 miles of range are gained in just 10 minutes of charging. Preconditioning the battery before charging, the Porsche Taycan averages 194kW power delivery while charging 10 to 80%. This is truly remarkable and while the 83.7kWh is a pricey optional extra, if you put the mileage in, it’ll be worth the investment.
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