GOOLOO GP4000 — 4000A, dual USB output

Still the unit we'd hand a stranger without instructions — but it is a different unit now. NOCO's GB70 that we used to rank here is gone from Amazon, and the Boost X GBX75 is its successor: 2500A of spark-proof, reverse-polarity-protected output that NOCO rates for engines up to 8.5L gas and 6.5L diesel, with a 60W USB-C Power Delivery port that recharges the pack in about 1.8 hours and runs back out to a phone or laptop. That port is the GB70's weakest point answered directly. Researched, not tested. The smaller GB40 below is the same UltraSafe safety system for a fraction of the money if your engine doesn't need this much headroom.

The value pick for people who want the pack to double as a laptop/phone bank: 2000A of starting power — enough for a big V8 — plus 65W USB-C PD that charges in and out. The 3.3-inch screen reports exact charge and fault state rather than making you guess at LED bars.

The glovebox standard for regular cars: 1000A is plenty for 4- and 6-cylinder gas engines, with the same spark-proof clamps as the pricier NOCO units. Skip it only if you run a large V8 or diesel that wants more amps.

The headroom option for big trucks and diesels: AVAPOW rates the A68 at 6000A peak and up to a 12L diesel, with an eight-layer clamp protection system and indicator lights that make a wrong connection hard to complete. It also works as a dual-USB power bank with a 3-mode LED light. Overkill for a commuter car, right-sized if you regularly start large diesel powerplants.