S ZEVZO ET03 Car Jump Starter 4000A Jump Starter Battery Pack for Up to 8.0L Gas and 7.0L Diesel Engines, 74Wh Portable 12V Jump Box with USB Ports, LCD Display, Storage Case, and LED Light

Why I started carrying the ET03

I tossed the ET03 into my trunk not because I expected to need it, but because I’ve learned the hard way that batteries die at the least convenient times. Over several weeks I used it in a mix of planned tests and genuine roadside moments—from an older pickup that had sat for months to a daily-driver SUV surprised by a cold morning. It proved itself as more than a one-trick emergency gadget; it’s a well-thought-out jump starter with a few smart extras and a couple of omissions worth noting.

Design and build

The ET03 is compact enough to live in a glove box, but I prefer the included hard-shell zip case—it keeps the unit, clamps, and cable tidy and protected. The pack feels solid, with rubberized surfaces that grip well on fenders and prevent sliding. The clamp leads are medium length; not the longest I’ve used, but flexible and easy to route. The clamps bite firmly and don’t deform under load, and the smart module in-line with the cables has clear indicator lights and an audible buzzer.

An LCD screen displays state of charge as a percentage, plus status indicators when connected. It’s simple and clear. There’s a multi-mode LED light (steady, strobe, SOS) on the pack that’s bright enough for under-hood work and roadside visibility without being blinding.

Setup and interface

Using the ET03 is straightforward:
- Charge the unit via USB-C before first use (more on charging below).
- Connect the clamps to the jump starter and then to the battery, red to positive, black to negative.
- The smart module confirms proper polarity with a green light and beep.
- Start the vehicle when the module signals it’s ready.

If the vehicle battery is severely depleted, the module gives error tones and instructions are printed on the clamp unit. There’s a force-start (boost) function that overrides detection for truly dead batteries. Critically, that boost requires the ET03 to be well charged—I had the best results with the pack at or near 100%.

Jump-start performance

On a healthy-but-low battery in a 5.3L gas SUV, the ET03 delivered instant cranking power. Turn the key and it’s like the battery magically found a second wind. On a cold morning, I performed three consecutive starts on the same vehicle without recharging the pack; each start dropped the ET03 by only a few percentage points. This tracks with the idea that the 4000A peak rating is marketing shorthand for “plenty of headroom.” I can’t verify the exact current, but it’s clearly robust for large gas engines.

On a 3.0L diesel, I deliberately ran the battery down with accessories. The ET03 had no trouble producing the initial surge needed for glow plugs and cranking; it started on the first try. Bigger diesels are typically the real test for jump packs, and while I wouldn’t call this overkill for all diesel scenarios, it’s far stronger than many compact jump starters I’ve used.

Across several vehicles (lawn tractor, motorcycle, midsize sedan, full-size pickup), I never saw the pack struggle when the vehicle’s battery had at least some voltage left. Average drop per start ranged from about 3% to 7% on the ET03’s display depending on engine size and temperature.

Recovering a truly dead battery (0V)

Where the ET03 distinguishes itself is the force-start function integrated into the clamps. I tested this with an old pickup that had sat long enough for the battery to read essentially 0V on a multimeter. In boost mode, the clamps bypass detection, and the pack dumps the needed energy immediately. The truck started on the second attempt. The key is to ensure the ET03 is fully charged before attempting this; with the pack below roughly three-quarters, boost starts were inconsistent. Fully charged, it behaved predictably.

There’s an important safety caveat here: boost mode assumes you’ve connected the clamps correctly. The module still provides cues, but you’re closer to a direct connection. The clamps’ beeper and lights help, and the grips are well-insulated, but treat boost mode with care.

Cold weather behavior

Cold saps both vehicle and jump-starter batteries. In temperatures in the low 20s°F, the ET03 still delivered reliable cranking. I kept the pack inside the cabin for a few minutes before use to avoid cold-soak, then walked it under the hood. Starts took slightly more effort, and the percentage dropped a bit more than in mild weather, but performance was still confidence-inspiring. The claimed operating range down to -4°F aligns with how it behaved for me; below freezing, planning and a full charge help.

Power bank and light

The ET03 doubles as a 74Wh power bank with two USB-A outputs rated at 5V/2A each. In practice, it charges a phone or tablet at the speed you’d expect from a standard 10W charger. There’s no Quick Charge or USB-C Power Delivery, so you won’t fast-charge modern phones or laptops. That said, for topping up a phone, running a dash cam in a pinch, or keeping a tire inflator that draws from USB fed, it’s handy. I used it during a power outage to keep a phone and a flashlight topped off and still had plenty of capacity left for a vehicle start.

The LED work light isn’t a headlamp replacement, but it’s practical for roadside use: it fills the engine bay enough to see what you’re doing, and the SOS mode adds a safety element if you’re pulled over at night.

Safety and protections

Reverse polarity detection works as advertised; I intentionally clipped the leads wrong during a test and got immediate error beeps and a red light, with no sparking. Over-current and short-circuit protection also behaved properly in contrived tests. The audible feedback is loud enough to hear on a roadside, and the indicators make troubleshooting simple. For users who don’t jump cars often, the combination of color-coded cues, beeps, and printed instructions on the clamp module goes a long way toward making the ET03 feel safe.

Battery life, charging, and standby

The ET03 charges over USB-C using a basic wall adapter. Input is limited to standard 5V charging, so topping it off from low takes a while; plan on a few hours with a 2A charger. I’d love to see USB-C PD input for faster turnaround. Once charged, it holds power well. Over a month in the trunk—checked weekly—I saw only a small drop in the state-of-charge percentage. I wouldn’t bank on any jump starter being “set-and-forget” for years, but monthly checks are easy, and the LCD percentage readout beats vague LED bars.

What could be better

• No fast-charge input/output: USB-C PD would greatly improve recharge times and device charging versatility.
• Lead length: The clamp cables are adequate but could be longer for awkward battery locations.
• No 12V accessory output: Some jump packs include a 12V barrel port; the ET03 doesn’t, which limits use with certain accessories.
• Boost mode dependency on high state-of-charge: This is expected, but it means you should be diligent about keeping the pack topped up if you anticipate 0V scenarios.

Who it’s for

• Drivers of larger gas engines or light-duty diesels who want a compact, reliable jumper.
• Anyone who often drives alone and wants self-sufficiency for dead-battery situations.
• Households with multiple vehicles, small engines (mowers, motorcycles), and the occasional need for a backup power bank.

If you need frequent fast charging for phones or laptops, or you rely on a 12V accessory port, you’ll want to pair this with other gear or consider a different style of power station.

Final thoughts and recommendation

The ET03 nails what matters most in a jump starter: dependable starting power, clear safety cues, and straightforward operation in real-world conditions. It started everything I threw at it, including a truly dead battery using the force-start function (provided it was fully charged). The LCD percentage readout removes guesswork, the included case keeps the kit organized, and the LED light is genuinely useful at night. As a power bank, it’s basic but practical.

I recommend the ET03 for anyone who wants a compact, confidence-inspiring jump starter with the muscle to handle larger engines and the smarts to be safe for occasional users. Its few omissions—no fast charging, no 12V accessory output—don’t detract from its core purpose. Keep it charged, stash it in the trunk, and it turns a potential roadside headache into a two-minute pit stop.