I drive a Citroën C5X plug-in hybrid. This was a great success with the motoring critics, which helped me make my decision, but a sales flop. I have not been at all disappointed; it suits my needs perfectly. The notional electric-only range is a maximum of 50km, falling to as low as 35km depending on conditions – hot/cold, using the air conditioning, etc. This is fine, as my daily commute is usually within this range, and I only rarely need petrol except for occasional longer trips. I usually charge it up every night on my home charger. My query is, given the frequent recommendation to only charge to 80 per cent, am I damaging the battery by charging to 100 per cent each night? Otherwise, the range would be insufficient. PK, Co Dublin
Plug-in hybrid cars (or PHEVs, plug-in hybrid electric vehicles, to give them their full name) often come in for criticism in the media, yet generally when we hear from actual owners of such cars, the reports are usually positive.
First off, we’re pleased to hear that you’re happy with your Citroën, and that you’re getting the best use out of it and making full use of its electric driving abilities. That is, after all, the whole point of having a PHEV. Also, kudos for buying the low and sleek C5X rather than a more predictable SUV – the C5X, now sadly out of production, is one of our favourite recent Citroëns.
Just this past month, environmental lobbyists Transport & Environment (T&E) were once again saying that such PHEVs emit six times as much in real-world driving compared to their claimed on-paper figures. That’s in spite of efforts by the EU to reset the way it officially tests the performance and emissions of such cars in an attempt to make the printed numbers more realistic.
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Even though T&E praised the likes of Volkswagen Group for offering vehicles with bigger batteries, longer electric range, and therefore lower real-world emissions, the group still fulminated that: “A decade after Dieselgate, it is outrageous that Europe is once again debating whether to keep using misleading emissions to sell cars. In ongoing negotiations on cars’ CO2, the European Parliament and Council have a clear choice: protect drivers’ wallets or allow carmakers to continue lying to consumers. Drivers deserve the truth, not another fix to protect carmakers’ profits while leaving drivers hundreds of euros out of pocket.”
T&E’s claim is that misleading plug-in hybrid electric vehicle figures add about €680 to their drivers’ fuel bills every year, but that clearly is not the case with you, and one suspects that many PHEV drivers are actually seeing overall savings in their bills, if they’re using the car correctly. Equally, that €680 figure is looking pretty cheap in relation to the Trump-related increases in everyone’s fuel bills this year.
Anyway, I’m drifting from the point somewhat, and you wanted to know about charging your PHEV’s battery to 100 per cent. The good news is that the short version is: you’re fine, keep charging it.
Why is that, when all the advice is to charge fully electric cars’ batteries to only 80 per cent unless you really need the extra capacity? It’s simply because we’re dealing with two different batteries doing two different jobs.
The battery of an electric car is its only source of power, and it has to last a long time, providing lots of kilowatts for driving and for running the car’s various support systems. It’s also extremely costly to replace one should it fail outside of warranty, so taking good care of your electric vehicle battery remains good advice (even if they’re way more robust in reality than we initially expected).
When it comes to plug-in hybrid electric vehicles, the battery is smaller, does a different job, and it’s also designed differently. Depending on the carmaker in question, you will find one of two things when it comes to charging to 100 per cent. Either the battery will say it’s at 100 per cent, but in fact there will be a considerable buffer of 10-15 per cent charge that you’re not seeing, or the battery will say 100 per cent, but as you drive it and drain it you’ll notice that the petrol (or, more rarely, diesel) engine kicks in once the battery display reaches about 20 per cent full. That’s because the battery of a plug-in hybrid has to keep a portion of its charge for driving as a regular hybrid. In other words, when the battery, electric motor, and petrol engine are all pulling together.
That buffer effectively means that you’re not actually charging the battery to 100 per cent each time. It’s why there’s often such a large discrepancy between the gross and net-usable capacities of a plug-in hybrid battery. For instance, VW’s latest PHEV batteries have a gross total capacity of 25kWh, but the amount that’s actually usable for all-electric driving is rated at 19kWh, leaving a substantial portion of battery charge in reserve. Your C5X has slightly less of a buffer – a gross capacity of 12.4kWh and a net usable capacity of 11.4kWh, but clearly someone in Citroën’s battery-making department reckoned it was enough.
Equally, while you can – and you clearly do – drive around on just the battery and electric motor for extended periods, the fact is that a plug-in hybrid electric vehicle’s electric driving system always has a backup – the petrol engine. If it’s too cold, or you ask for more power or more distance driven than the battery and motor can provide on their own, then the petrol engine will be called into life. That’s the whole point of having it, really.
It sets up an interesting debate for the coming couple of years. While much of the focus is – rightly – on all-electric cars, given the continuing paucity of the national charging network, there will be many car buyers who will still not be willing to trust electric-only power.
For those buyers, car makers are increasingly starting to make plug-in hybrid electric vehicles with longer electric ranges. For instance, Volvo is just introducing a new version of the evergreen XC60 SUV with a 200km electric-only range.
Chinese brands BYD and Zeekr are planning new PHEV models with 160-200km electric ranges, and some may offer as much as 300km. Already, VW Group has several models – VW Golf, Audi A3, Skoda Superb, Cupra Formentor – that can reach as much as 140km on the official Worldwide Harmonised Light Vehicle Test Procedure test on battery alone (and about 100km to 110km in real-world conditions). It will be interesting to see how such longer-range PHEVs appeal to the car-buying public.
Meanwhile, as far as your Citroën is concerned, well, wear it and don’t worry about charging it up fully.
