Battery Testing

Our next subject to cover was batteries and how to test them. For these exercises we had to use a 12v battery, digital multimeter, hydrometer and a high rate discharge tester, otherwise known as a load tester.
 
              Inspecting for battery specifications

For this area of the exercise we had to carry out visual inspections on the battery.

Make of battery: Lucus                            
CCA: 460 Cold cranking amps
Type of battery:  Conventional
Can you get to the electrolyte? Yes
Explain how: Unscrew the cap and remove them.

Are the terminals on the battery clean and tight? Yes
Does the battery show signs of swellings? No
Do any of the areas above require attention? No

                       Checking electrolyte levels

In order to check the electrolyte levels, we must first adorn the required safety gear. Safety glasses and gloves are important because if there is a problem with the battery, or the battery is knocked, battery acid could be poured onto your skin or clothes and cause severe burns, if it gets in your eyes you could be permanently blinded. Safety measures are important with testing batteries for those reasons, but also because the battery acid and fumes around the battery are highly flammable, it is important to keep them in an area away from anywhere or anything that there is a spark. To check the electrolyte levels, we simply look inside the cells to see where the battery fluid is resting. If it is above the cell plates the electrolyte levels are alright and do not need any topping up, if the top of the cell plate is sticking up above the electrolyte then the levels need to be topped up.

Cell 1 Level           Ok
Cell 2 Level           Ok
Cell 3 Level           Ok
Cell 4 Level          Ok
Cell 5 Level          Ok
Cell 6 Level          Ok

                  Battery open circuit voltage test

In order to complete an OCV test on the battery, we must first establish that all possible surface charge has been removed otherwise we will obtain an incorrect reading. To remove surface charge you must turn on the vehicle headlights to drain off the surface charge for around two minutes, turning them off and waiting for a minute and then checking the OCV. OCV is checked by placing the voltmeter on the battery terminals using DC volts as a range.

What voltage did you get? 12.54v
What is the state of charge? 75%-100%
What voltage reading equates to 50% charged? 12.4v
Can you continue with the battery test using this battery? Yes
If the battery happened to be too discharged to load test, what further action would you take? The battery should be left to charge, then be rechecked, but if the battery is still showing below 50%, then the battery would need to be replaced.

                      Testing the battery electrolyte specific gravity

A hydrometer is used to check the specific gravity readings in a battery. To do this, you must place the hydrometer in the battery fluid, then squeeze the top so it pulls the battery fluid up when you release the top. The float inside the hydrometer will tell you the specific gravity. Becareful not to take the hydrometer out of the battery fluid when you are measuring the specific gravity, as battery fluid will drip out of the bottom. This is also an opportunity to inspect the colour of your fluid, which can indicate whether or not your cell plates are corroding, depending on the colour. Grey means that your negative plates are corroding, and brown means that your positive plates are corroding, clear means that there is nothing wrong with your battery plates.

Cell 1 Reading & Colour           1.275 - Grey
Cell 2 Reading & Colour           1.275 - Grey
Cell 3 Reading & Colour           1.275 - Grey
Cell 4 Reading & Colour           1.275 - Grey
Cell 5 Reading & Colour           1.275 - Grey

Cell 6 Reading & Colour           1.275 - Grey
Specific gravity variation of battery:      0
What is the allowable specific gravity variation of your battery: 0-50%
Does the specific gravity of your battery pass? Yes

                        High rate discharge test

Next we must use a load tester to determine the batteries ability to supply cranking voltage, however to perform this test the battery must have at least 50% charge. Make sure that your load tester is swithed off before connecting the leads. Connect the positive lead to the positive terminal on the battery, connect the negative lead to the negative terminal of the battery and apply the specified load by turning the load control knob, the specified load is half of the cold cranking amperage. Wait for the specified time, which is 20 seconds, and take the voltage held and the current readings. When the tester is done, it will beep. Turn off the load tester and disconnect the leads in the reverse order of which you connected them.

What was the voltage held while load was applied? 9v

What was the load current held? 230amps

The reading of 9v is a failed result.The load current held was a pass.

                   Battery Report


What do you recommend needs to be done with this batteryand system?
It would need replacement at some point in the near future due to the corroding negative plates inside the battery cells.

If the terminals were corroded, how would you clean and protect them?
To clean and protect the terminals, you can use a mixture of water and baking soda, however then you must hose off the battery and chassis straight away to avoid rust.

If the battery needed charging, how would you charge it and for how long?
You would charge the battery with a battery charger. You can fast charge the battery for half an hour if you had left your headlights on, this must be charged on 20amps. You can also overnight charge if you just have a flat battery, you must have this on low amps though so as not to overcharge the battery and cause swelling. Overnight charge is usually 12-24 hours.

If the amp draw was too high, how would you track down the problem?
To track down an amp draw, you would use an amp meter and unplug each of the fuses one by one and test them to see which is draining the most amps from the circuit.

The next task we had to was test the battery using a Digital Battery Tester. To test the battery, we must first have the ignition key turned off. Make sure all the battery terminals are clean before connecting the positive clip to the positive terminals and the negative clip to the negative terminal. It will flash up with an error message if your connection is poor. If the battery needs charging, the tester will flash 'CH' or nothing at all, place this battery on charge for a while before continuing. If 'SAE' flashes up on the screen, the tester is working and once you have seen it, you can then set up the tester to the CCA rating of the battery using the controls, make sure that the tester is programmed to 'SAE' first though. Press the test button and wait for the results, if the screen flashes 'PASS' it means that the battery is in good condition and there has been no faults detected. If it flashes 'FAIL', that means something is wrong and you must remove the battery, clean it up and test it again, as sometimes dirty battery terminals can give false results. If it flashes 'SF.CH', that means that the tester has picked up that the battery is carrying some surface charge, which will need to be expelled before testing can continue.

What reading did you get on the display? Fail
What does this tell you about the battery? This tells us that the battery will need replacement.

We then pressed the 'test' button again, which displays the open circuit voltage of the battery and will allow us to work out the state of charge.

What was the OCV of the battery? 12.6v

Pressing the 'test' button again, will give you the cold cranking amperage at that point in time.

CCA: 250

What is the state of charge of the battery? 100%

From the information collected, we would replace the battery due to the failed result on the digital tester and the negative plates being corroded. Alternatively, we could conduct some tests on the charging system to see if there is any fault in there that could be affecting the battery.