2. Testing
2.1. There are two reasons for testing a battery. First, to find out if the battery is good or bad (serviceability); Second, to determine how much charging, if any, it needs (state of charge).2.1.1. Serviceability
To determine if a battery has reached the end of its life, a Load Test is performed. If the battery passes the Load Test, it is good and may be reinstalled in the vehicle. See section 2.4 for the Load Test procedure.
2.1.2. State of Charge
To determine how much charge a battery has, and therefore how much more it may need, a No-load Test is performed. There are two types of No-load Tests available, a Hydrometer Test (see section 2.2) or Voltmeter Test (see section 2.3). The Hydrometer Test is more accurate. but the Voltmeter Test is faster. When in doubt use the Hydrometer Test.
A battery must not fall below 75% charged for an extended period of time or permanent damage will result.
2.2. Hydrometer Test
Either a hydrometer or a refractometer may be used for this test. A hydrometer requires temperature compensation, and the electrolyte level in the battery must be above the "MIN" mark. Add water if necessary, mixing the water in by gently shaking the battery.
A refractometer needs only a drop of electrolyte, and automatically compensates for temperature. If the battery has just been charged, allow it to stand disconnected for at least 30 minutes to ensure an accurate reading.
2.2.1. Measure, and record on battery test sheet, the electrolyte density in each battery cell using a hydrometer or refractometer. Adjust the reading for temperature if using hydrometer.
2.3. Voltmeter Test
An accurate digital multi meter must be used for this test. The Voltmeter Test is less accurate than the Hydrometer Test, but takes less time to perform. The battery MUST sit disconnected for at least 30 minutes; or at least 60 minutes if just charged before performing this test: Failure to observe the correct waiting times will result in erroneous readings.
2.3.1. Measure open circuit battery voltage of disconnected vehicle battery at electrolyte temperature between 60 ° and 100 °F. Indicate results on battery test sheet.
2.4. Load Test
For the Load Test to be valid, the battery must be at least 75% charged. If the battery was just charged, remove the "surface charge" by loading the battery at 150 Amps for 10 seconds before testing.
WARNING!
A large amount of energy is released from the battery during this test. Observe all safety precautions.
2.4.1. Disconnect the vehicle negative - battery terminal and then the positive + terminal.
2.4.2. Measure and record electrolyte temperature of center cell.
2.4.3. Connect an approved volt-amp tester to the battery as per manufacturers instructions. Ensure a good connection.
2.4.4. Connect an accurate digital voltmeter across the battery terminals.
2.4.5. Cover the battery with a wet, clean shop cloth.
2.4.6. Apply a test load to the battery equal to three times the Amp-hour rating. For example, test a 100 Ah battery at 300 amps. Read the battery voltage at 15 seconds and remove load. Record value on test sheet.
2.4.7. If observed voltage is greater than or equal to the minimum voltage shown in chart below (dependent upon electrolyte temperature) the battery is in good condition and should not be replaced. If the observed voltage is less than the minimum voltage, recharge the battery (see section 3) and retest.