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SAE J2185: Life Test for Heavy-Duty Lead-Acid Storage Batteries (2018)
This standard defines a life test procedure for 12 V heavy-duty lead-acid storage batteries used in starting, lighting, and ignition (SLI) applications on motor vehicles and off-road machines. It simulates severe usage patterns—high daily starts, loads exceeding charging system output—and ensures batteries can endure repeated cycling at elevated temperatures. Batteries are classified into Type 1 (reserve capacity ≤ 250 min) and Type 2 (reserve capacity > 250 min), and the test continues weekly until failure per defined voltage thresholds.
Scope and Battery Classification
SAE J2185 applies to lead-acid batteries as referenced in SAE J537 and SAE J930. The test classifies batteries into two types based on reserve capacity (RC):
- Type 1: BCI group sizes with RC ≤ 250 minutes.
- Type 2: Larger batteries with RC > 250 minutes.
This classification determines the charge and discharge current limits used throughout the test. All batteries must be pre-conditioned per SAE J537 and should begin the life test within 90 days of manufacture unless otherwise agreed.
Test Procedure and Key Parameters
The test is conducted in a water bath maintained at 50 °C ± 1.7 °C (122 °F ± 3 °F). Each weekly cycle consists of 26 alternating charge/discharge sequences, a rest period, and a cold cranking performance test. The table below summarizes the weekly regimen:
| Step | Flooded Type 1 | Flooded Type 2 | VRLA (All Types) |
|---|---|---|---|
| Charge (2.5 h) | 14.80 V, 25 A max | 14.80 V, 50 A max | ≥14.0 V (per manufacturer) |
| Discharge (1 h) | 25 A | 50 A | Same currents as flooded |
| Stratification removal (4 h) | 5 A or 1% CCA | 10 A or 1% CCA | Not required |
| Rest period | 57.5–68 h | 57.5–68 h | 61.5–72 h |
| Cold cranking test (50 s) | CCA rate at -18 °C | CCA rate at -18 °C | CCA rate at -18 °C |
After the rest period, the battery is discharged at its cold cranking amperes (CCA) rating for 50 seconds at 50 °C. The minimum voltage requirement at 50 seconds is 7.20 V. The test is considered complete when the battery fails to meet this 7.20 V threshold or fails to sustain 10.5 V during any regular discharge cycle. Cycle life is defined as the number of successful weeks prior to failure.
Important Considerations and FAQs 🛠️
Engineering Design Insight: Batteries must withstand repeated deep cycling at 50 °C to pass SAE J2185. Flooded batteries require periodic water addition with distilled or deionized water only—tap water introduces impurities that reduce performance. VRLA batteries (AGM or gel) do not require the electrolyte stratification removal step and have a longer rest period. Proper classification (Type 1 vs Type 2) is critical for selecting correct current limits.
⚠️ Common Mistakes: Using tap water, neglecting preconditioning, starting test with batteries older than 90 days, applying incorrect current limits (25 A vs 50 A), or confusing flooded and VRLA charging voltage requirements (14.80 V vs ≥14.0 V).
What voltage must the battery maintain during the cold cranking test?
The battery must maintain at least 7.20 V during the 50-second discharge at its CCA rating.
At what temperature is the life test conducted?
The test is run at a constant 50 °C ± 1.7 °C (122 °F ± 3 °F) in a water bath.
How is the life test considered complete?
The test ends when the battery fails to meet the 7.20 V threshold during the cold cranking test or fails to sustain 10.5 V during any discharge cycle (4.3.1.2). The life is the number of cycles that have successfully passed the weekly 50-second discharge requirements.
Why is water quality critical for flooded batteries?
Distilled or deionized water must be used to avoid impurities that can adversely affect battery life and performance. Overfilling should be avoided, and a short mixing charge is recommended after any water addition.
An optional post-test teardown analysis may be performed within 60 days to determine failure mode; this should be done on a fully charged sample if battery condition permits. For full details, refer to SAE J2185 (2018) and related standards SAE J537 and SAE J930.
