BMW i3 Battery Capacity Loss: Warranty Coverage – What Dealers Won’t Tell You (And How CNS BATTERY Actually Protects Your Investment)

“My 2018 i3 dropped from 27 kWh to just 19 kWh usable in three years. I took it to the dealer—still under BMW’s ‘8-year battery warranty.’ They ran a test, smiled politely, and said: ‘Your capacity is at 72%. The warranty only covers complete failure—not degradation.’ I walked out with a $14,000 quote for a new pack… and a sinking feeling I’d been misled.”

You watch your range shrink month after month.
You count fewer bars on the dashboard.
You dig up your warranty paperwork and think:

“If my battery fails, I’m covered… right?”

The harsh reality?

Most factory warranties—including BMW’s—exclude gradual capacity loss unless it falls below an arbitrary threshold (often 70% or lower). By then, your i3 is already severely compromised.

But what if your replacement battery came with clear, enforceable, degradation-based coverage—not fine-print loopholes?

In this guide, you’ll learn:

• The truth about BMW’s official i3 battery warranty (and why it rarely helps real-world owners)
• How CNS BATTERY defines capacity loss—and guarantees protection
• The exact metrics used to validate a claim (no guesswork)
• Why third-party packs often offer better warranty terms than OEM
• And the one document you must keep to prove your case

Because when your battery fades, your warranty shouldn’t vanish with it.

BMW’s Official Warranty: Strong on Paper, Weak in Practice

BMW advertises an 8-year / 100,000-mile high-voltage battery warranty for the i3. Sounds robust—until you read the fine print:

“Coverage applies only if battery capacity falls below 70% of original AND the vehicle is within warranty period.”

But here’s what they don’t emphasize:

• 70% of a 33 kWh pack = 23.1 kWh—yet many owners report driving anxiety below 25 kWh
• Dealers use proprietary ISTA tests that may not reflect real-world usable capacity
• No coverage for imbalance, power limitation, or slow charging—only total failure or extreme degradation

📉 Real-world data: Most i3 owners experience noticeable range loss by year 4–5, long before hitting the 70% cliff.

Result? Thousands pay out-of-pocket for replacements while still “under warranty.”

✅ CNS BATTERY Warranty: Built for Real Degradation

At CNS, we believe warranty should match driver experience—not corporate thresholds. That’s why our coverage is different:

✔️ Clear Capacity Guarantee

• 2-year / 80,000 km warranty (whichever comes first)
• Capacity must remain ≥75% of rated value (e.g., ≥37.5 kWh for a 50 kWh pack)
• Measured via BimmerLink or equivalent OBD2 tool—no dealer gatekeeping

✔️ Dashboard Bar Standard

• Original i3 display shows 12 bars when new
• Warranty valid as long as ≥9 bars remain after full charge
• Simple, visual, and owner-verifiable

✔️ Covers Both Pack and Modules

• Whether you buy a full pack or individual modules, degradation claims are honored equally

“At 18 months, my CNS 45kWh pack showed 34.1 kWh usable (75.8%). When it dipped to 33.6 kWh (74.7%) at 23 months, CNS sent a replacement module—no arguments.”
— Lisa K., Berlin

No loopholes. No runaround. Just proof—and support.

How to Document Capacity Loss (So Your Claim Stands)

To qualify under any warranty, you need evidence. Here’s how to collect it properly:

1. Charge fully using AC (Level 2, overnight)
2. Let car rest 2+ hours (no doors opened, no app access)
3. Open BimmerLink → HV Battery → Usable Capacity (kWh)
4. Take a screenshot showing:
   • Date/time
   • VIN (if possible)
   • Exact kWh value
5. Repeat 3x over 7 days to confirm consistency

💡 Pro tip: Also record dashboard bar count—it’s accepted as secondary proof by CNS.

Keep these records. They’re your leverage.

Why Third-Party Warranties Often Outperform OEM

📌 Key insight: CNS sets a higher standard because we use new CATL cells with slower degradation curves. We can afford stronger coverage—because failures are rare.

What Voids Your CNS Warranty (And How to Avoid It)

We stand by our packs—but protection requires responsible use:

❌ Opening the pack housing without CNS authorization
❌ Installing without following wiring diagrams
❌ Using non-certified chargers that cause voltage spikes
❌ Ignoring thermal warnings and continuing to drive

✅ Safe practices that keep coverage intact:

• Use OEM or certified EVSE
• Follow recommended charging habits (avoid chronic 100% holds)
• Contact CNS before attempting any HV work

When in doubt, ask us first—we respond within 24 hours.

Frequently Asked Questions: i3 Battery Warranty & Capacity

Q: Does BMW cover labor for battery replacement under warranty?

A: Only if the pack is deemed defective—not for degradation. Even then, approval is rare.

Q: Can I get a CNS warranty extension?

A: Not currently—but our 2-year term aligns with typical early-failure windows.

Q: What if my i3 is older than 8 years but I install a CNS pack?

A: Full warranty still applies—from your CNS delivery date, regardless of vehicle age.

Q: Do you require professional installation for warranty validity?

A: No—but improper installation that damages the pack voids coverage. We provide free remote guidance.

Q: How fast is a CNS warranty claim processed?

A: Most are reviewed within 48 hours. Approved replacements ship in 5–10 business days.

Don’t Bet on a Warranty That Leaves You Stranded

Factory promises sound comforting—until you need them.
Then you discover: coverage ≠ protection.

Get a Battery Backed by Real Degradation Guarantees

With CNS BATTERY, your investment is shielded by transparent terms, measurable standards, and a team that responds—not deflects.

Stop hoping your OEM warranty will save you. Choose one that actually does:
👉 https://cnsbattery.com/ev-battery-home/ev-battery-contact/