A granny charger is the cable that plugs your electric car into a standard 13A household socket at one end, and into your car’s charging port at the other. It gets its nickname from the idea that almost anyone has a normal three-pin plug socket available, even at a relative’s house. More formally it’s called a Mode 2 cable, and the safety electronics built into the cable itself make it considerably more sophisticated than it looks.
If you’ve just collected a new EV and found a cable coiled in the boot, this is almost certainly what it is. Below we cover how it works, how fast it charges, what the box on the cable does, and what to watch for if you ever shop for a replacement.
The IC-CPD: the safety brain inside every Mode 2 cable
The rectangular box moulded into the cable, usually sitting somewhere between the 13A plug and the Type 2 connector, is called the IC-CPD: In-Cable Control and Protection Device. It is the defining component of a Mode 2 cable, and the feature that distinguishes a legitimate granny charger from a simple extension lead with EV connectors bolted on.
| Component | Description | Key spec |
|---|---|---|
| BS 1363 13A Plug (wall end) | Standard UK three-pin plug | Current limited to 10A by IC-CPD |
| IC-CPD Box (mid-cable) | In-Cable Control and Protection Device | IEC 62752 compliant; IP55; earth fault protection; thermal cut-out; pilot signal to car |
| Type 2 Connector (car end) | IEC 62196-2 EV connector | Standard on all new UK EVs sold since approx. 2018 |
What the IC-CPD actually does
The IC-CPD, governed by IEC 62752 (In-Cable Control and Protection Device for Mode 2 cables), performs four core functions:
- Pilot signal communication. Before any power flows, the IC-CPD sends a control pilot signal to the car confirming the cable is connected and ready. The car must respond before charging begins. If the connector isn’t properly seated, nothing happens.
- Earth fault protection. The IC-CPD continuously monitors the earth connection and cuts power if an earth fault is detected, protecting both the car and the user.
- Over-current protection. The device enforces the 10A current limit, preventing the cable from drawing more than the socket circuit is safely designed to handle.
- Thermal monitoring and cut-out. Temperature sensors within the IC-CPD watch for overheating in the cable, the box, or the plug. If temperatures exceed safe thresholds, the IC-CPD cuts power automatically. This is a feature rarely mentioned in competitor guides, but one we consider essential to understand before an overnight charging session.
Thermal cut-out: why it matters for long overnight sessions
An overnight charge on a domestic socket is a sustained load, typically eight hours or more. The IC-CPD’s thermal cut-out is an active safety mechanism, not a passive component. It is there precisely because long-duration low-current charging on a domestic socket creates gradual heat build-up at the plug pins and socket contacts, particularly in older or worn sockets. If you notice a charge session that stopped unexpectedly overnight, a thermal cut-out event is one of the first things to investigate. It may mean the socket itself needs inspection.
How fast does a granny charger charge your car?
At 10 A on a 230 V supply, a granny charger delivers approximately 2.3 kW. That translates to roughly 8 miles of range added every hour. Leave it plugged in overnight for eight hours and you’d typically recover around 60-65 miles, enough for most daily commutes, though far slower than a dedicated Mode 3 home charger.
The maths: 10A × 230V = 2,300W = 2.3kW. At 2.3kW, and assuming a typical EV efficiency of around 3.5 miles per kWh, you get roughly 2.3 × 3.5 = ~8 miles per hour of charging. (Your car’s actual figure will vary with battery chemistry, temperature, and onboard charger efficiency, but 8 miles per hour is the widely used rule of thumb.)
| Label | Value | Unit |
|---|---|---|
| Mode 2 Granny Charger (10A / 2.3kW) | 8 | miles/hr |
| Mode 3 Wallbox 16A (3.7kW) | 15 | miles/hr |
| Mode 3 Wallbox 32A (7.4kW) | 30 | miles/hr |
The 10A rule: why 13A is a red flag
A compliant Mode 2 granny charger must limit current to 10A, not 13A. Any unit that allows 13A continuous draw from a domestic socket is non-compliant and represents a genuine fire risk.
A standard UK 13A socket and its associated wiring are designed to handle brief peak loads at 13A (a kettle for three minutes, for example). They are not designed for sustained high-current charging sessions lasting many hours. Prolonged 13A draw can overheat the wiring in older ring mains, the socket contacts, and the plug itself.
Our warranty and returns experience at EV Cable Hub bears this out: cables from unregulated general marketplaces are disproportionately present in cases involving socket scorching or unexpected trip events. We can’t put precise figures on that (our first-party data is qualitative) but the pattern is consistent. If a listing advertises a granny charger at 13A or “full 13A power”, treat it as a warning and look elsewhere.
The 10A limit is codified in IEC 62752. The standard exists for a reason.
IEC 62752: the standard that defines every legitimate granny charger
IEC 62752 is the international standard for the IC-CPD used in Mode 2 EV charging cables. Published by the International Electrotechnical Commission, it defines the electrical, mechanical, and functional requirements every legitimate granny charger IC-CPD must meet.
What the standard requires
Key requirements of IEC 62752:
- Current rating: Maximum 10A for use with domestic sockets (the BS 1363 13A plug in UK homes).
- Protection functions: Earth fault protection, over-current protection, and temperature monitoring with automatic disconnection.
- Pilot signal: The IC-CPD must implement the IEC 61851-1 control pilot function to communicate with the vehicle before charging begins.
- Ingress protection: The IC-CPD enclosure must meet at least IP55, protected against dust and water jets. Fine in rain, snow, or a hosepipe splash; not rated for submersion.
- Mechanical strength: Cable and connectors must pass defined stress tests for outdoor domestic use.
When a granny charger carries IEC 62752 compliance, those requirements have been independently tested. When it doesn’t, you have no such assurance.
When should you use a granny charger?
Genuine emergency backup use
The granny charger genuinely excels as an emergency backup charging option. If you’re visiting somewhere without a wallbox, staying in a holiday cottage, or your regular charge point is temporarily out of service, a 13A socket is almost always available. Plug in overnight and you’ll typically have enough range to continue your journey or reach a faster charger the next morning. The ability to charge almost anywhere is why the cable is worth keeping in the boot.
Why most manufacturers advise against daily use
Most vehicle manufacturers explicitly advise against using a granny charger as your primary charging method. This is not a legal prohibition. It’s a practical and safety recommendation rooted in the sustained load placed on domestic socket circuits over many consecutive nightly charge sessions.
The IET Code of Practice for EV Charging Equipment Installation, 5th edition (2023) reinforces this position, recommending a dedicated Mode 3 wallbox as the preferred domestic charging installation. The reasoning covers both charging speed and circuit integrity: a dedicated charging circuit is sized and installed specifically for the task, whereas a standard ring-main socket is not.
If you’re relying on a granny charger day-to-day because you rent and can’t install a wallbox, that’s understandable. Just ensure the socket is in good condition, avoid extension leads, and have the socket inspected if you notice warmth at the plug during a session.
Granny charger vs Mode 3: what’s the real difference?
Mode 2 puts the safety electronics in the cable itself (the IC-CPD), allowing use with any domestic socket. Mode 3 places the control and protection functions in fixed charging equipment, a wallbox or public charge point, and uses a dedicated circuit. Mode 3 delivers 16A (~3.7kW) to 32A (~7.4kW), roughly double to four times the speed of a granny charger.
The practical implications:
| Mode 2 (Granny Charger) | Mode 3 (Wallbox) | |
|---|---|---|
| Standard | IEC 62752 (IC-CPD in cable) | IEC 61851-1 (fixed equipment) |
| Current | 10A | 16A: 32A |
| Power | ~2.3kW | ~3.7kW: 7.4kW |
| Charge rate | ~8 miles/hr | ~15-30 miles/hr |
| Installation | None: any 13A socket | Electrician required |
| Best for | Emergency / travel backup | Daily home charging |
For a deeper look at how the two modes compare across all the variables that matter, see our guide on Mode 2 vs Mode 3 charging.
What to look for when buying a Mode 2 cable, and what to avoid
A granny charger is safe when it complies with IEC 62752 and is limited to 10A. Units sold on unregulated marketplaces that allow 13A draw pose a genuine fire risk. A standard 13A socket and its wiring are not designed for sustained high-current charging loads. Always buy from a specialist retailer, not a general marketplace listing.
Beyond compliance, here’s what we look for when assessing a Mode 2 cable:
- IEC 62752 compliance stated explicitly: look for the standard number, not just a vague “safety certified” badge.
- 10A current rating confirmed. If you see 13A advertised as a feature, walk away.
- IP55 IC-CPD enclosure: necessary for any outdoor socket use.
- Type 2 (IEC 62196-2) connector on the car side. Standard on all new UK EVs since approximately 2018; check if your car is older.
- Appropriate cable length. Most drivers find 5m sufficient at home; 8-10m is useful when travelling.
For a full breakdown of which cable suits which situation, our guide to which EV charging cable you need covers the decision in detail.
Frequently asked questions
What is a granny charger?
A granny charger is a Mode 2 cable that charges your electric car from a standard UK three-pin socket. It has a built-in IC-CPD safety device, is governed by IEC 62752, and delivers roughly 2.3 kW, about 8 miles of range per hour.
Is a granny charger safe?
A compliant granny charger, one that meets IEC 62752 and limits current to 10A, is safe for occasional use on a sound domestic socket. Non-compliant units that allow 13A continuous draw are a genuine fire risk. Always buy from a specialist retailer and look for explicit IEC 62752 compliance.
How long does it take to charge an EV with a granny charger?
At 2.3kW (10A, 230V) you add approximately 8 miles per hour. Eight hours overnight typically recovers around 60-65 miles. That is enough for most commutes, but much slower than a Mode 3 wallbox.
What does IC-CPD mean?
IC-CPD stands for In-Cable Control and Protection Device, the box between the 13A plug and the Type 2 connector. It provides earth fault protection, communicates with the car via a pilot signal, monitors temperature, and cuts power automatically if the cable or socket overheats. It is standardised by IEC 62752.
Can I use a granny charger every day?
Most vehicle manufacturers advise against it as your sole charging method. The IET Code of Practice for EV Charging Equipment Installation (5th edition, 2023) recommends a dedicated Mode 3 wallbox for regular domestic use. Treat a granny charger as emergency backup or occasional top-up, not a daily routine.
What’s the difference between a granny charger and a Mode 3 charger?
Mode 2 puts safety electronics in the cable (IC-CPD) for use with any socket. Mode 3 builds protection into fixed wallbox equipment on a dedicated circuit. Mode 3 delivers 16A (3.7kW) to 32A (7.4kW), two to four times faster.
What does IP55 mean on a granny charger?
IP55 means the IC-CPD is protected against dust and water jets from any direction. Fine in rain, snow, or a hosepipe splash. Not rated for submersion: don’t leave it in standing water.
Why do some marketplace granny chargers advertise 13A? Is that safer?
No. It’s a red flag. Domestic socket wiring isn’t designed for sustained 13A loads over many hours. Prolonged 13A draw risks overheating wiring, contacts, and the plug. Compliant cables per IEC 62752 cap at 10A for this reason. Avoid any unit that lists 13A as a feature.
Browse our full Type 2 cable range to find your fit.