AUTOMOTIVE BATTERY

This week we learned how to test the automotive battery and tested the the battery on car.

First day we tested a battery off car. The battery made by LUCAS, battery number is 128HD, cold cranking amps is 400A, conventional type.

Before we start the test, we need to carry out some visual checks first to see if any corrosion under mounting clamp, terminals clean and tight, clamp bolts tight and no electrolyte leakage on case. The battery that we were testing had no problem.

A hydrometer has been used to test the electrolyte in the battery, because the electrolyte contants H2SO4, we need to put on a pair of safety glasses and wearing gloves before remove the battery cell covers, and need to know where is the closest water supply if and accident happened.

After remove the battery cell caps, we need to check the electrolyte level in each cell first. All six cells were showing a high level.

Then we tested the open circuit voltage of that battery, was showing 6.60V, refer to the table in our test book, we can find this battery was under 25% charge, as we know the battery must be over 50% charged 12.4V before we can continue the testing. We put the battery back onto the charger and changed to another one.

The hydrometer designed to do the battery electrolyte specific gravity test, we put the hydrometer front end into each of the battery cells, sucked up about half tube of electrolyte, checked the reading and coulor showing in the hydrometer. The readings are, 1.250(white), 1.225(red), 1.250(white), 1.300(green), 1.200(red), 1.200(red), the battery sepccific gravity variation we tested is 100 point. But the allowable spec is 25-50 points, that means the battery has failed this test.

After the off car testing, we moved on to the on car testing of the battery. The battery we were tesing made by LUCAS, number NS40ZLG for a 1998 mazda demio, CCA 310.

Before start testing we also carried out a visual check like the off car testing. That battery was in good condition, no corrosion, all bolts tight, terminals clean, and no leakage on case.

Checked all six battery cells level in high level, we performed an ocv test, reading was 12.6v, more than the half charge spec 12.4v, that means the battery in good working order. After that, we tested the spec gravity by using the hydrometer, all readings between 1.235 to 1.265 and showed green in colour.

Last test was the high rate discharge test, we hooked on the load test onto the battery and applied a current of 155A, which is half of the CCA of that battery,  the voltage of that battery was hold above 10.6V.

From the battery testing, I found when we work with batteries, we need to make sure put all safety equipments on, perform visual check first, electrolyte must at high level other wise fill it up with still water. the ocv must more that 12.4v, and spec gravity reading needs between 1.235 to 1.265, high discharge test needs to know the cca rate before put the load on, and load only can put on less than 15sec, if any of these tests failed, the battery either needs to be charged or needs to be replaced.