A resistor hidden in your charging cable decides how fast your EV charges
Four things limit AC charging, and the charging post is usually the least important of them.
Plug into a 22 kW post, come back an hour later to find seven kilowatt-hours in the battery, and the natural suspicion is that the post is broken or lying. It is neither. Charging on alternating current is a negotiation between four participants, and the slowest one wins every time: the cable in your hand, the onboard charger built into the car, the number of phases actually reaching the socket, and whatever current the post has left once the car beside you has taken its share. The post advertises the ceiling of that negotiation, never its result. The cable is the participant almost nobody thinks about, because it does not merely carry current, it declares a limit. Inside the plug of every Type 2 cable, wired between the proximity pilot pin and earth, sits one resistor whose value is the cable's entire vocabulary: 100 ohms means 63 amps, 220 ohms means 32 amps, 680 ohms means 20, and 1500 ohms means 13. The post reads that resistor before anything else happens, lowers its own limit to match and passes the figure on to the car. A cheap spare cable coded at 13 amps will hold a 22 kW post and an 11 kW car to roughly 3 kW between them, all night, without producing a single error message.
The onboard charger is the limit you either paid for or did not
A charging post on AC is little more than a switch with a meter in it. The actual conversion from alternating current to the direct current a battery can absorb happens inside the car, in a box called the onboard charger, and its rating is a hard ceiling nothing outside the car can raise. Three ratings dominate Europe: 7.4 kW, which is 32 amps on one phase, 11 kW, which is 16 amps across three phases, and 22 kW, which is 32 amps across three. The trap is that on plenty of models the 11 kW unit is an option, and a single-phase 7.4 kW charger is what arrives if nobody ticked the box. That decision, made once by whoever ordered the car, then governs every overnight charge for the rest of its life, and it is worth checking on a used EV before you calculate how long the commute takes to replace. This is also the cleanest explanation of why one car can accept 150 kW at a motorway stop and 7.4 kW at home: rapid charging on direct current bypasses the onboard charger entirely and feeds the pack from outside, which is the whole architectural reason flash charging can push power figures that no AC post will ever approach. The AC number and the DC number are two different components, and the sales brochure rarely separates them.
Germany caps single-phase cars at 4.6 kW, and Belgium has streets where three phases are not three phases
Two national grid quirks catch drivers who assume electricity is electricity. German connection rules, set out in VDE-AR-N 4100, cap the imbalance between the three phases of a domestic supply at 4.6 kVA, which is why anything drawing more than that has to be spread across all three conductors. In practice a single-phase car on a German wallbox is often held to 20 amps, around 4.6 kW, rather than the 7.4 kW its onboard charger could take, and nothing is faulty when that happens. Belgium has the opposite problem. Parts of the country, along with pockets of France and Norway, still run 3x230V delta grids with no neutral conductor, and three-phase charging equipment is generally designed for 3x400V. On such a connection some cars fall back to one or two phases and some refuse to start at all, so an owner who specifically paid for an 11 kW onboard charger can find their driveway incapable of delivering it. The fix is a transformer to convert delta to a standard star topology, which is an electrician's job and a real cost, and it is worth establishing which grid your street is on before ordering a wallbox rather than after.
A public post with two sockets is one connection wearing two hats
The kerbside posts that dominate Dutch, Belgian and German cities almost always carry two sockets, and in most cases both hang off a single grid connection. Load balancing then divides the available current between whoever is plugged in, which means an 11 kW session quietly becomes something closer to 5.5 kW the moment a neighbour arrives, mid-charge, with no notification and no fault. That is normal behaviour rather than a defect, and it is the reason two people can compare notes on the same post and describe entirely different experiences. Where it starts to cost money is on the tariff. Charging billed per kilowatt-hour is indifferent to how slowly you go, but plenty of European operators bill per minute or add a time-based connection fee, and under those a car that draws half the power pays twice as much for the same energy. Knowing your car's genuine AC ceiling is therefore not trivia: it tells you whether parking an 11 kW car on a 22 kW post billed by the minute is a convenience or a straightforward overpayment.
Cold weather is a DC problem, and it is not what is slowing your wallbox
Owners frequently blame temperature for slow home charging, and on AC that is almost never the culprit. A cold battery limits how fast it can safely accept charge, but the threshold at which that limit bites sits well above the 7 to 11 kW an AC post delivers, so a frozen car on a wallbox charges at more or less its usual rate. It simply spends some of the energy warming itself and heating the cabin rather than filling the pack, which shows up as a worse consumption figure rather than a lower power reading. Direct current is where cold genuinely costs you, sometimes halving the rate a rapid charger will offer, and it is the reason battery preconditioning exists and why the charger is rarely what decides how fast an EV charges. If a home charge has genuinely slowed down over a winter, look at the cable, the wallbox's own current setting and whether the car's timer or a solar-surplus mode is throttling it, before concluding the battery is to blame.
What to actually do
All of this is settled in about five minutes with the cable in your hand and the car's manual open, and once settled it does not need revisiting.
Read the amperage moulded or printed on your Type 2 cable, usually on the plug body or a collar near it. If it says 13A or 20A, that is your real ceiling, whatever the post or the car can do.
Own one good cable rather than two cheap ones. A 32 amp three-phase five-metre cable covers every public post in Europe and costs roughly what a tank of fuel does.
Look up your car's onboard AC charger rating in the manual, not the brochure, and note whether it is single-phase or three-phase. On a used EV, confirm it before you buy.
Treat the granny cable that came in the boot as emergency equipment. At 10 amps it adds roughly 2.3 kW, which is a full night for about 100 kilometres of range.
Before ordering a wallbox in Belgium, ask your installer whether the supply is 3x230V without neutral or 3x400V. It decides whether a three-phase car will ever charge at three-phase speed there.
Check the tariff before plugging into a fast AC post. Per-minute billing punishes a slow car; per-kilowatt-hour billing does not care.
If a public session suddenly halves, look at the socket next to you before reporting a fault. Two sockets on one connection share what is available.
Check the current limit set in your own wallbox app. Installers routinely dial it down to protect a fuse and then never mention it.
Frequently asked questions
Why is my EV charging at 7 kW when the post says 22 kW?
Almost always because your car has a single-phase 7.4 kW onboard charger, which is the most common rating in Europe and a hard ceiling the post cannot raise. The other two candidates are a cable coded for fewer amps than the post can supply, and a second car sharing the same connection. Working out which is straightforward: try the same car on a different cable, and if nothing changes, the limit is inside the car and permanent.
Does an expensive charging cable charge faster than a cheap one?
Not because of price, but because of the rating, and the two often correlate. A cable is defined by two things: the cross-section of its copper and the resistor that declares what that copper can carry. A 32 amp three-phase cable will let a capable car draw 22 kW; a 13 amp cable will not, no matter how well made it is. Buy on the amp and phase rating printed on the plug, ignore the marketing, and make sure the length suits the awkward parking spaces rather than the easy ones.
What is the difference between AC and DC charging speed?
They use different hardware, which is why the numbers are so far apart. AC charging pushes mains current into the car and lets the car's own onboard charger convert it, so it is limited by that small converter, typically 7.4 to 22 kW. DC rapid charging does the conversion in the roadside cabinet and feeds the battery directly, bypassing the onboard charger, which is how 150 kW and more becomes possible. A car with a modest AC rating can still be a quick DC charger, and the reverse is equally true.
Can I upgrade my car's onboard charger later?
In general no. On most models it is a physical component fitted at the factory, not a software setting, and retrofitting it is either impossible or costs more than the time it saves is worth. A small number of manufacturers have offered a paid software unlock where the hardware was already capable, so it is worth one question to a dealer, but plan on the rating you have. That is precisely why it deserves checking before you sign for a used EV rather than after.
Is charging slowly on AC bad for the battery?
The opposite. Slow alternating-current charging is the gentlest way to fill a pack, generating little heat and putting the least stress on the cells, which is why manufacturers recommend it as the everyday default and treat rapid charging as the exception for journeys. An overnight charge at 3 kW is not damaging anything; it is simply inconvenient if you needed the range by morning. The only real cost of charging slowly is time, and money where the tariff is measured in minutes.
