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2020 S60 T5 Battery Drain & Start-Stop Not Working - '12V Battery Critical Charge'

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Mike T. · rep 0 · May 22, 5:15 AM · 1 replies · solved · Question

Vehicle: 2020 Volvo S60 T5 Momentum

My 2020 Volvo S60 T5 Momentum has been acting up lately. For the past few weeks, I've been getting a '12V Battery Critical Charge' message on the dash, and the start-stop function has completely stopped working. If I don't drive it for a day or two, it struggles to start, almost like the battery is dead.

I had the battery tested at an auto parts store, and they said it was 'good' but a bit low. I've tried trickle charging it, which helps for a bit, but the problem always comes back. Could something be draining the battery, or is the battery actually failing despite the test?

It's really annoying, especially since the car isn't that old. Any advice on what to check next?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:15 AM

0

ClearTheCode admin answer:

The '12V Battery Critical Charge' message, combined with start-stop malfunction and slow starting, strongly suggests a parasitic battery drain or a failing battery, even if it tested 'good' under a basic load test. Modern Volvos are very sensitive to battery voltage for all systems, especially the start-stop feature.

Troubleshooting Steps:

  1. Full Battery Test: Get a professional battery test that includes a CCA (Cold Cranking Amps) check. A battery can show good voltage but fail under load. Volvo's start-stop system requires a battery in peak condition.
  2. Check Charging System: Ensure your alternator is properly charging the battery. A failing alternator can lead to undercharging. You can check the voltage across the battery terminals with the engine running; it should be around 13.8-14.4 volts.
  3. Parasitic Draw Test: This is crucial. With the car off and all doors closed, use a multimeter to measure current draw from the battery. It should drop to a very low level (typically under 50mA) after the car's modules 'go to sleep' (which can take 15-30 minutes). If it remains high, a component is staying active and draining the battery.
  4. Check for OBD Codes: Even without a check engine light, a scan tool might reveal codes related to battery voltage or charging. Look for codes like P0562 (System Voltage Low) or P0620 (Generator Control Circuit Malfunction).

Common Causes:

  • Weak/Failing Battery: The most common cause. Even a relatively new battery can fail prematurely.
  • Parasitic Drain: A module (e.g., infotainment, telematics, comfort access) not shutting down properly, or a faulty accessory.
  • Alternator Issues: Not providing sufficient charge.
  • Battery Management System (BMS) Fault: The BMS might be misinterpreting battery status or failing to manage charging correctly.

When to See a Shop:

  • If a new, fully charged battery doesn't resolve the issue.
  • If you detect a significant parasitic draw but can't pinpoint the source.
  • If the alternator output is incorrect.
  • If the diagnostic scan reveals specific fault codes related to the charging system or battery management. A Volvo specialist can perform advanced diagnostics to identify the exact module causing a parasitic drain.
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