Slow charging at home is usually caused by one of five things: the charger is set to a low current, the car has a charging limit set, the battery is cold, the supply voltage is lower than expected, or the charger is reducing current because it is getting hot. Charging also slows naturally as the battery gets close to full.
Find the Cause
| Check | What you might find |
|---|---|
| Charger current setting | Set to 16 A instead of 32 A or 40 A |
| Car charging current limit | Reduced in the car’s charging menu |
| Battery temperature | Cold battery charging slowly while heating |
| Voltage | 208 V in some buildings instead of 240 V (about 13% less power) |
| Heat derating | Hot plug, outlet or charger in sun |
| Load management | Charger reducing current when the house uses more power |
| Level 1 only | A 120 V cord adds just 3–5 miles per hour |
What Normal Speed Looks Like
At 240 V, a 32 A charger delivers about 7.7 kW and a 40 A charger about 9.6 kW, if the car accepts it. Expect roughly 25–30 miles of range per hour. See charging time at 7, 11 and 22 kW.
Fixes
- Raise the charger’s current to match the circuit, never above 80% of the breaker rating.
- Check and reset the car’s current limit.
- In winter, schedule charging to finish just before departure.
- Have an electrician check a warm outlet or low voltage.
Chargers with a display, such as the EVDANCE EV-ACS4005T 40A NACS portable charger, show live current and power so you can see what is limiting the session.
Frequently Asked Questions
Why is my Level 2 charger so slow?
Check current settings in the charger and car, battery temperature and voltage.
Why does charging slow down near 100%?
The car tapers current to protect the battery.
Why is my Level 1 charger so slow?
Level 1 is inherently slow, about 3–5 miles per hour.
Related Reading
- Why Is My Electric Car Charger Not Working?
- How Many Amps Does an EV Charger Need?
- Cold-Weather EV Charging
Key Takeaways
- Low current settings, cold batteries and low voltage are common causes.
- 208 V supplies deliver about 13% less power than 240 V.
- Heat derating signals an outlet or ventilation problem.