How to Use an EverStart Maxx Battery Charger

An EverStart Maxx battery charger is a multi-mode charger sold at Walmart in several configurations — most commonly as a 15-amp or 40-amp unit with modes for charging, maintaining, and jump-starting. These chargers are designed to work with standard 12-volt lead-acid batteries found in most passenger vehicles, as well as AGM (absorbed glass mat) batteries common in newer cars, trucks, and SUVs.

Understanding how to operate one correctly protects both your battery and your vehicle's electronics.

What the EverStart Maxx Charger Can Do

Depending on the model, EverStart Maxx chargers typically offer several operating modes:

Not every EverStart Maxx model includes all four modes. Check the label on your unit and the printed guide before assuming a mode is available.

Before You Start: What to Check

⚡ Battery type matters. Most EverStart Maxx chargers have a switch or dial to select between standard flooded lead-acid and AGM battery types. Using the wrong setting can overcharge or undercharge your battery. Check your owner's manual or the battery label — it will say "AGM," "Flooded," or "Conventional."

Voltage matters too. Nearly all passenger cars and light trucks use 12-volt batteries. Some heavy equipment uses 6-volt or 24-volt systems. EverStart Maxx chargers are primarily designed for 12-volt applications. Using one on a mismatched voltage system can cause damage.

Battery condition. A deeply discharged battery (below ~10.5 volts) may not respond to a standard charge cycle. Some EverStart Maxx models include a "desulfation" or "repair" mode for deeply discharged batteries, but not all units do — and severely damaged batteries sometimes can't be recovered by any charger.

Step-by-Step: How to Use It

1. Turn the charger off before connecting anything. Never attach or detach the clamps while the charger is running.

2. Identify the battery terminals. The positive terminal is marked with a + sign (usually red). The negative terminal is marked with a − sign (usually black). Connecting them in reverse can damage the charger, the battery, and your vehicle's electrical system.

3. Connect the red (positive) clamp first to the positive terminal. Then connect the black (negative) clamp to a solid metal ground on the vehicle — ideally an unpainted bolt or bracket away from the battery, not the negative terminal itself. This reduces the risk of a spark near the battery, which can release hydrogen gas.

4. Select your battery type using the mode dial or switch — flooded vs. AGM.

5. Select your charge mode. For a standard depleted battery, use the regular charge setting. For long-term storage, use the maintain or trickle mode. Avoid high-amp fast charging repeatedly — it generates more heat and shortens battery life over time.

6. Plug in the charger and power it on. The display will show voltage, charge status, or amp output depending on the model. Some units run a diagnostic before beginning to charge.

7. Wait for the charge cycle to complete. A fully depleted battery on a standard 15-amp charge can take anywhere from 4 to 12 hours depending on battery capacity (measured in amp-hours or CCA rating). Most EverStart Maxx units automatically taper the charge rate as the battery fills — you don't need to time it manually.

8. Power off the charger before disconnecting. Remove the black (negative) clamp first, then the red (positive) clamp.

Using the Engine Start / Boost Mode

🔋 The boost or engine-start function is meant for situations where the battery has enough capacity to start the car with a short high-current assist — not to replace a fully dead battery. If your battery is completely dead, standard charging first is a better path than repeated boost attempts.

When using boost mode:

• Keep the charger connected to the battery
• Do not operate the charger's controls while standing near the battery
• Attempt the start within the time window specified in your charger's manual — typically a few seconds
• If the vehicle doesn't start after a couple of attempts, let the battery charge for at least 30 minutes before trying again

Variables That Affect How Well This Works

The same charger can produce very different results depending on the situation:

• Battery age — A battery older than 4–5 years may not hold a full charge even after a complete cycle
• Battery size — Larger batteries (higher amp-hour ratings) take longer to charge
• Temperature — Cold weather slows chemical reactions inside the battery; charging a frozen battery can cause it to crack or rupture
• State of discharge — A battery that's been deeply discharged for weeks is harder to recover than one that just ran down overnight
• Vehicle electronics — Some modern vehicles draw a small amount of power even when off. If your vehicle has a parasitic drain, the battery may discharge again shortly after charging

What Charging Won't Tell You

A fully charged battery isn't necessarily a healthy battery. 🔍 A battery can accept and hold a charge temporarily but still fail a load test — meaning it can't deliver enough current to start the engine under real conditions. Most auto parts stores offer free battery load testing, which is a better indicator of true battery health than charge level alone.

How long your charged battery lasts, whether a replacement makes sense, and what battery spec fits your vehicle are questions shaped by your specific make, model, climate, and how the vehicle is used — none of which a charger's display can tell you.