How to choose a portable EV charger

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A portable charger is a small box between a big car and an outlet you may never have seen before. That makes the specifications that sound boring -- the listing, the adjustability, the plugs -- the ones that matter most. Here are the six checks, in order, with a unit that gets each one right.

1. The connector

A J1772 portable charges nearly every EV sold in North America, including a Tesla through the adapter that comes with it. A NACS portable plugs straight into a Tesla or a native-NACS car but needs an adapter for a J1772 car. If more than one car in the family might use it, J1772 is the flexible choice. Plug types explained.

2. Current, and whether you can turn it down

On a NEMA 14-50 wired for 50 A, 40 A is the most a portable can use continuously -- 9.6 kW, about 34 miles of range per hour. Just as important is turning it down: the J+ Booster 2 offers settings from 6 A to 40 A, and Lectron's Level 1 & 2 unit runs 8 to 12 A on 120 V and 16 to 40 A on 240 V. That is how you charge safely on a weaker or unfamiliar circuit.

3. Plugs and adapters

At minimum you want a 14-50 for Level 2 and a standard outlet for Level 1. The J+ Booster 2 includes both adapters and sells 5-20, 6-15, 6-20, 6-50 and TT-30 adapters separately; Lectron's Level 1 & 2 unit has switchable 5-15 and 14-50 plugs; the Lectron J1772 portable comes with a 14-50 plug and a standard-outlet adapter. Travel outlet guide.

4. The safety listing

This is the check with no trade-off. Look for a listing from a recognized laboratory, stated plainly: the J+ Booster 2 publishes ETL certification to UL standards, and Lectron publishes UL 2594 / UL 2231 certification for its NACS portables. If a listing cannot be found, ask the seller before buying -- how to read certification wording.

5. Cable length

Outlets are rarely where the charge port is. The J+ Booster 2 comes in 21 ft and 25 ft versions; the Lectron J1772 portable has a 21 ft cable. Measure the real distance from outlet to port before you buy, and never bridge a gap with a household extension cord. Cable length guide.

6. Ruggedness

A portable gets dropped, rained on and occasionally driven over. The J+ Booster 2 publishes an IP67 rating and resistance to 6,600 lb wheel loads -- the kind of claim worth looking for if the charger will live outdoors or in a truck bed.