ChargePapa T4A portable EV charger showing over-amperage warning — circuit sizing guide for 15A vs 20A outlets

EV Charger Showing "Over Amperage" Warning? Here's Why It Happens at Max Current

ChargePapa Knowledge Hub · Troubleshooting Guide
EV Charger Showing "Over Amperage" Warning?
Here's Why It Happens at Max Current
Last updated: May 2026 · 6 min read · ChargePapa Team
You set your portable EV charger to 16A and it immediately throws an over-amperage warning. Drop it to 10A and it works fine. The answer is almost always the same: your circuit cannot sustain the continuous draw your charger is requesting. The charger is protecting itself — and your wiring.
Troubleshooting Portable EVSE Circuit Sizing

You set your portable EV charger to its maximum current — 16A — and it immediately throws an over-amperage warning. Drop it to 10A and it works fine. This is one of the most common questions we receive from portable EVSE owners, and the answer is almost always the same: your circuit cannot sustain the continuous draw your charger is requesting. The charger is protecting itself — and your wiring — by refusing to run at a current your circuit can't safely support.

Why a 16A Charger Triggers Over-Amperage on Its Own Maximum Setting

NEC Article 625 requires EV charging to be treated as a continuous load — expected to run for 3 hours or more. For continuous loads, the circuit must be rated at 125% of the maximum draw.

A 16A portable EVSE running continuously requires a 20A circuit (16A × 1.25 = 20A). Most standard household outlets are on 15A circuits — not designed to supply 16A continuously.

Charger Setting Continuous Load Rule (×1.25) Minimum Circuit Required
8A 10A 15A circuit (minimum)
10A 12.5A 15A circuit
13A 16.25A 20A circuit
16A 20A 20A dedicated circuit
Key takeaway

A 15A circuit safely handles 12A continuous — which is why reducing to 10A or 13A often clears the warning immediately.

Step-by-Step Diagnosis

1
Identify your circuit rating

Look at the breaker protecting the outlet you're using. The rating is printed on the breaker handle: typically 15A or 20A.

  • 15A breaker + 16A charger = over-amperage at max setting is expected
  • 20A breaker = 16A continuous is within spec
2
Remove any extension cord

An extension cord adds resistance → voltage drop → charger interprets it as overloaded circuit → same warning triggers even on a 20A circuit. Connect directly to the wall outlet. NEC Article 625 prohibits extension cords with EVSE.

3
Step-down test
  • Set to 10A → charge 10 min → no warning = circuit handles lower loads
  • Set to 13A → charge 10 min → if warning returns = circuit is the limit
  • Set to 16A → if warning returns after clearing at 13A = circuit confirmed undersized
  • Warning at all settings including 8A → likely a device fault, not circuit. Contact support with order number.
4
The correct fix

Install a dedicated 20A / 240V outlet (NEMA 14-50 or NEMA 6-20) on a 20A circuit with 12 AWG wiring. Standard electrician job, typically 1–3 hours.

Interim solution: Set the charger to 80% of your circuit rating for continuous use — 15A circuit → set to 12A max.

What the Over-Amperage Warning Actually Means

Different portable EVSE brands label this differently: "over current," "OCP fault," "circuit overload" — all mean the same thing: the charger measured a current or voltage condition that exceeds safe parameters and shut down the session to prevent damage. This is the charger working correctly. It's not a defective unit.

Cases where the charger itself may be at fault (not the circuit)

  • Warning appears at 8A on a confirmed 20A dedicated circuit with no extension cord
  • Warning appears inconsistently on the same outlet
  • Charger is warm or hot to the touch during the warning

If any of these apply: contact info@chargepapa.com with your order number for device-level diagnosis.

For Home Installation — Getting Circuit Sizing Right

Wallbox / EVSE Max Current Required Circuit Wire Gauge
Portable 16A 16A 20A dedicated 12 AWG
ChargePapa V1 / V2 (32A) 32A 40A dedicated 8 AWG
ChargePapa V8 (48A single-phase) 48A 60A dedicated 6 AWG

Always have a licensed electrician confirm your panel has available capacity before adding an EV circuit.

Frequently Asked Questions

My charger works fine at 13A but trips at 16A — is it broken?
Almost certainly not. 13A continuous requires a 16.25A circuit — just within a 20A circuit's limit. 16A continuous requires a full 20A circuit. If your outlet is on a 15A circuit, 16A will trip it. The charger is correctly refusing to overload the circuit. Solution: use a 20A outlet, or set the charger to 12A max for the 15A circuit you have.
Can I use a heavy-duty extension cord rated for 20A?
No. NEC Article 625 prohibits extension cords with EV supply equipment regardless of the cord's rating. Even a properly rated cord adds resistance that causes voltage drop under continuous load, triggering overcurrent protection. Always connect your EVSE directly to the wall outlet.
How do I know if my outlet is 15A or 20A?
Look at the outlet itself: a standard 15A outlet has two vertical slots. A 20A outlet has one vertical and one T-shaped slot. More reliably, check the breaker in your panel — the amperage is printed on the breaker handle.

Related: Why Is My EV Charger Tripping the Breaker?

ChargePapa portable EVSEs support adjustable current settings so you can match the charger's draw to your circuit's capacity. For permanent installation, the V1 and V2 wallboxes are designed for dedicated 40A circuits.

Related Engineering Notes