2022–2026 BMW i4
Save $132 by doing it yourself! Shop cost: $350
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| Part Name | Part Number | Price | Buy |
|---|---|---|---|
| 12V Battery | 12V-AGM-70 | $200.00 | |
| Battery Terminal Cleaner | — | $10.00 | |
| Battery Terminal Protector Spray | BTP-200 | $8.00 |
About prices: shown prices are estimates from typical Amazon listings and change frequently, and cheaper alternatives may be available. Confirm the current price on Amazon before buying.
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Follow these steps carefully
Park on level ground and set the parking brake. Power the vehicle fully off and remove the key/fob from the cabin if required by the maker. On EVs and PHEVs the 12V auxiliary battery is often in the frunk, cargo area, under a rear seat, or under a cover — not always under the hood. Wear gloves and eye protection.
Open the access panel and identify the 12V battery (or remote jump posts). Confirm positive (+) and negative (−) markings. Do not confuse the high-voltage traction battery orange cables with the 12V system — leave orange HV connectors untouched.
Check for corrosion, loose clamps, frayed cables, or a swollen/leaking case. Clean light corrosion with battery terminal cleaner and a brush if needed. Ensure the hold-down is snug so the battery cannot move.
With everything off, set a digital multimeter to DC volts. Probe positive then negative. A healthy resting 12V battery is typically about 12.4–12.7 V (AGM similar). Below ~12.0 V suggests a discharged or failing battery that needs charge/test.
Start the engine or put an EV in Ready (per the owner’s manual). Recheck voltage at the battery or jump posts. Alternator/DC-DC charging is usually ~13.5–14.7 V. Much lower or much higher can indicate a charging-system fault.
Turn on headlights and blower briefly and watch for a large voltage drop. If resting or charging voltage is out of range, charge and retest or replace the 12V battery with the correct AGM/flooded type. Close covers securely when finished.
Test your repair before closing everything up. If something doesn't work right, double-check your steps.
⚠️ Common Mistakes to Avoid
