2013–2020 Mercedes-Benz SL
By Ray Delgado ✓ Certified Mechanic · Published Sep 21, 2026 · Updated Oct 22, 2026
Save $135 by doing it yourself! Shop cost: $315
Quick answer: 12V Battery Replacement on a 2013–2020 Mercedes-Benz SL is rated Moderate and takes about 30-90 minutes. You'll need 2 tools for this job, and parts cost about $180. This guide walks you through the full job step by step, including the mistakes to avoid.
| Part Name | Part Number | Price | Buy |
|---|---|---|---|
| Replacement 12-volt battery for 2013-2020 Mercedes-Benz SL; verify group size, CCA, terminal layout, and VIN fitment | — | $180.00 | |
| Anti-corrosion terminal protectant or felt washers (optional) Optional | — | $8.00 |
About prices: shown prices are typical retail averages and change frequently; cheaper alternatives may be available. Confirm the current price before buying.
💡 Pro tip: Order all parts at once to save on shipping
Follow these steps carefully
Note that ECO start-stop models also carry a small separate 12-volt 12Ah AGM auxiliary battery; this guide covers the main trunk battery. Photograph the old label before shopping.
Park the SL on level ground, set the parking brake, switch the ignition fully off, and remove the key or fob from the car. Open the trunk and remove the right-side rear paneling and the frame around the stowage compartment to expose the battery. Wear gloves and eye protection.
The battery tie-down is easy to overtighten. I go snug — crushing the case causes leaks you won't see until it's too late.
Remove the positive terminal cover and photograph the cable routing, the hold-down bracket with its retaining strap, and the vent hose connected to the battery. Check the terminals and bracket for corrosion before touching any fasteners.
Detach the ground (negative) cable from the battery first and set it where it cannot touch a terminal. Remove the positive terminal cover, then detach the positive cable and lay it aside. Keep tools clear of body metal — the trunk cavity is tight.
Detach the vent hose from the battery, then unscrew the bracket nuts and lift the bracket and retaining strap off as one unit. Lift the old H8 AGM battery straight out — at nearly 60 pounds, get help than wrestling it past the trunk trim.
Lower the new H8 AGM battery into the compartment in the same orientation, refit the bracket and retaining strap, and tighten the nuts securely. Reconnect the vent hose to its port.
Start the SL and confirm strong cranking with no battery or charging warnings. Expect roughly 13.5 to 14.5 volts across the terminals with the engine running. Some R231 builds need the new battery registered to the onboard energy management — check your owner's manual, and if warnings persist, have a Mercedes-capable scan tool complete the registration.
Test your repair before closing everything up. If something doesn't work right, double-check your steps.
⚠️ Common Mistakes to Avoid
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