Used EV Buying Guide: How to Check Battery Health Before You Buy

Buying a used electric vehicle can save you thousands compared to new—but there's one critical component that can make or break the deal: the battery. A used EV with a healthy battery is a fantastic value. One with a degraded battery could cost you more than you saved.

This guide will show you exactly how to evaluate a used EV's battery health, what numbers to look for, and how to avoid the most common mistakes buyers make.

Why Battery Health Matters More Than Mileage

With traditional cars, mileage is king. A 100,000-mile car has more wear than a 50,000-mile car. With EVs, it's not that simple. A high-mileage EV that was gently charged at home might have better battery health than a low-mileage one that sat in hot climates or was constantly fast-charged.

What SoH Should You Look For?

Here's a quick guide based on vehicle age and what's considered acceptable:

• 1-2 years old: Expect 95-98% SoH (anything below 93% is concerning)
• 3-4 years old: Expect 90-95% SoH (below 88% needs investigation)
• 5-6 years old: Expect 85-92% SoH (below 82% is below average)
• 7+ years old: Expect 80-88% SoH (below 75% may have issues)

These are general guidelines. Some EVs (like older Nissan Leafs without active cooling) degrade faster, while others (Tesla, BMW, newer Hyundai/Kia) tend to hold up better.

How to Check Battery Health Before Buying

Method 1: Use VoltChek (Free Estimate)

Before you even see the car, get a baseline estimate. Enter the make, model, year, and mileage into VoltChek to see what battery health you should expect. If the seller's claims are significantly different from this baseline, that's either a red flag or a pleasant surprise worth verifying.

Method 2: Check the Car's Built-in Display

Some EVs show battery health information directly:

• Tesla: Energy app shows degradation indirectly through max range at 100% charge
• Nissan Leaf: Battery capacity bars on the dashboard (12 bars = 100%)
• BMW i3/iX: Hidden menu or dealer scan shows exact SoH percentage
• Chevrolet Bolt: Energy screen shows estimated range at full charge

Method 3: Use an OBD-II Scanner

For the most accurate reading, use an OBD-II Bluetooth adapter with a compatible app. Popular options include LeafSpy (for Nissan), Scan My Tesla, or the generic Car Scanner app. These show exact SoH percentages and individual cell voltages.

Method 4: Request a Dealer Battery Health Report

If buying from a dealer or certified pre-owned program, ask for a battery health certificate. Many manufacturers now provide these. If they can't or won't provide one, consider that a yellow flag.

Red Flags to Watch For

Walk away or negotiate hard if you notice any of these warning signs:

• Seller refuses to let you check battery health or see a full charge
• Range at 100% is significantly lower than EPA rating (accounting for age)
• Car was primarily used for rideshare/taxi (higher fast-charging frequency)
• Vehicle spent its life in extremely hot climates (Arizona, Texas, Middle East)
• Charging takes much longer than it should at DC fast chargers
• Any battery-related warning lights or messages in the system

How Much Should Battery Degradation Affect Price?

Battery health should directly impact what you pay. Here's a rough negotiation guide:

• 90%+ SoH: Full market value—this is a healthy battery
• 85-89% SoH: Negotiate 5-10% off asking price
• 80-84% SoH: Negotiate 10-15% off—you're losing noticeable range
• 75-79% SoH: Negotiate 15-25% off—battery replacement may be needed within 3-5 years
• Below 75%: Think carefully—potential replacement costs $5,000-$15,000+

Check Remaining Warranty Coverage

Most EV batteries are warrantied for 8 years or 100,000-160,000 km, with a guaranteed minimum capacity (usually 70%). If the car is still under warranty and the battery drops below that threshold, you could get a free replacement.

The Pre-Purchase Checklist

Before signing any paperwork, make sure you've done the following:

• ✓ Got a VoltChek estimate to know expected battery health
• ✓ Verified actual SoH using one of the methods above
• ✓ Checked remaining warranty coverage (time and mileage)
• ✓ Asked about charging habits (home vs. fast charging ratio)
• ✓ Checked where the car spent most of its life (climate matters)
• ✓ Looked for any battery-related service history
• ✓ Test drove with a full charge to verify real-world range

The Bottom Line

A used EV with good battery health is one of the best automotive values available today. You get the benefits of electric driving—low fuel costs, minimal maintenance, smooth performance—at a significant discount from new prices.

The key is doing your homework before you buy. Check the battery health, understand what the numbers mean, and negotiate accordingly. A little research now can save you thousands later.

Start by getting a free battery health estimate for any EV you're considering. It takes 30 seconds and gives you the baseline knowledge you need to buy with confidence.