Over the past two decades (maybe even longer), you’ve heard of the importance of battery and electrical systems testing. Voltagedrop testing goes back for as long as I can remember. Battery testing, too. In the old days, you might find someone considering the battery as OK if it operated the starter. A sophisticated shop would invest $30 in a load tester (Figure 1). I was in my 20s when I bought this one. It was the best way to check batteries at the time because it measured the voltage while loading the battery. If you look closely, its maximum Cold Cranking Amps (CCA) was 300. The electrical demands were pretty low back then. You can still find this type of battery tester online and at auto parts stores, although I‘m having a hard time knowing why you’d want one.
From there, we turned to measuring a battery’s minimum voltage. A fully charged battery would have 12.66 volts. The minimum you’d want was 12.4, and at 12.2, the battery was considered discharged. You’d start the car while your voltmeter was attached to the battery and measure the lowest voltage while turning over the engine. You could set the min/max feature of your DVOM to capture the lowest value. It worked pretty well. The minimum voltage for a good battery was around 10 volts. The voltage depends on the temperature. At freezing temperatures, it could get down to 9 volts. The next step would be to measure the voltage while the engine is running. This checks the alternator. You’d expect around 14.5 volts for this test1. Tests like these were the gold standard for years. However, it required understanding electronics testing principles and interpreting variations in the test results.
A capable battery is essential to ensure your customer’s car can operate the vast and complex systems of today’s vehicles. The ATRA Tech Department has seen countless problems fixed by testing, cleaning, and fully charging the vehicle’s battery. Some shops even offer a battery service to extend its performance.
Let’s examine what happens to a lead-acid battery as it ages. Three things occur over time:
- Sulfation: Crystals that form on the lead plates. This is similar to the corrosion you see on the posts. It’s additional resistance and lessens the battery’s capacity.
- Corrosion: Similar to sulfation, but it includes a disintegration of the lead plates.
- Stratification: This is when the acid becomes unevenly distributed in the battery. Denser acid sinks to the bottom while diluted acid remains on top.
All of these affect the capacity of the battery. Traditional testing can hide these problems, so let’s look at an alternative: The battery conductance tester. This technology isn’t new, but you may not be familiar with it.
You can find a range of conductance testers on the market. Mine happens to be the Midtronics PBT-300 (Figure 2). It costs about $300 and is great for personal use. Notice the caption, which points out buttons and lights. We’ll refer to them later. They make other models with features like 24-volt testing and a built-in printer. The printer allows you to give your customer the results of your test.
Conductance testing is effective because it can test a discharged battery or one that is not fully charged. The conductance tester will say, essentially, “The battery is fine. It just needs charging.” On the other hand, it’ll spot internal failings on a fully-charged battery and alert you that it’s reaching the end of its life. Think of it like the battery on your cell phone. When it was new, a full charge would last several days. After five years, you can barely get a day’s use of it. Yet, in both cases, a fully-charged battery performs the same, whether new or old. The only difference is the battery life. The same is true with a car battery. Traditional tests may not reliably detect a failing battery or one close to failing.
How’s it work? The tester delivers a small a/c voltage to the battery and measures how well that voltage runs through it. This checks the sulfation, corrosion, and stratification mentioned above. It’s not a panacea, though. An over-charged battery will fail the test. If you measure battery voltage and it’s over 12.70 or so, the tester will likely condemn the battery. In this case, let the battery sit for a while or operate a few accessories to get the voltage around 12.6. You may be surprised to see that the battery is now testing perfectly. We’ll touch on this a bit later. With that, let’s get started, and I’ll show you how easy this is:
Before you begin: Make sure the battery is clean and the cables are in good condition. If the battery and terminals look like the example in Figure 3, correct these conditions before testing the battery. If you’d like to test a battery in this condition, you can isolate it from the vehicle by removing the cables and following the conductance test outlined in steps 1 and 2. If the battery tests okay, clean the cables and any connections and continue with step 3.
Step 1, Settings: Determine the battery’s capacity. Depending on the battery’s origin, it’ll be listed by:
- CCA (Cold Cranking Amps).
- EN (European Norm)
- IEN (International Electrotechnical Commission)
- DIN (Deutsches Institut für Normung)
Figure 4 shows a partial chart for a comparison of these ratings. Figure 5 shows an example of CCA, and Figure 6 shows an example of DIN (I don’t have examples of EN or IEN).
CCA is the most popular in the US, and even many vehicles imported from Europe and Asia will include a CCA rating along with other ratings they use. Cold Cranking Amps rating is the number of amps a battery can deliver at 0° F for 30 seconds while maintaining at least 7.2 volts. The other ratings are similar but with different specifications and may include dimensions and terminal types, such as the DIN standard.
Step 2, Testing the Battery’s Condition: Connect the tester to the battery. This tester defaults to 500 CCA (Figure 7). Press the up arrow to increase the CCA setting or down to lower it. Once you have the right setting press the test button. You’ll see the tester lights work (like it’s thinking) and then display a number showing how close the battery came to operating at that rating. In our first example, we tested a battery rated at 650 CCA. Unfortunately, the tester only provides a setting of 640 or 660. We’ll select 660 CCA.
After the tester goes to work, it returns a value of 616 and shows a green “OK” light (Figure 8). The number it displays is the calculated CCA of the battery based on the behavior of the a/c signal it sends to the battery for the test. It then compares that to the battery’s rating. If the tested value is below a certain threshold, then it illuminates an LED (or two in some cases) that indicates the battery’s condition. This battery is in great shape.
Step 3, Alternator and Starter Testing: These tests measure battery voltage while starting the engine and running. You could use a DVOM for this, but the tests are so quick and easy you might as well do it while the tester is connected. Before you continue, make sure your battery is fully charged. Press the blue button marked “V.” If your voltage is less than 12.4, charge the battery before proceeding. Our test vehicle had 12.46 V.
Now start the engine and raise the rpm to about 2,000. Hold it there for about 15 seconds. When you started the engine, the tester measured the cranking voltage and is now measuring the alternator’s output. After the 15-second test period, shut off the engine and check the tester.
Press the down arrow, and the tester displays the stored cranking voltage. Our example showed 10.68 V. It also shows a green (OK) LED on the testing panel (Figure 9). Had the meter read an excessive drop in voltage, it’d illuminate the Red “Repair/Replace” LED.
Now press the up arrow (Figure 10). The tester showed the highest average voltage when the engine was running. In our case, it was 14.33 V.
This next battery is rated at 430 DIN (Shown in Figure 6). To switch from CCA to DIN, hold down the test button while connecting the tester to the battery. It’ll show the last rating standard it used. In our case, it displays CCA but with periods between each letter. This means it’s in setup mode. Press the up arrow until you get to “din” Figure 11. Once there, you press the “test button, and it begins the test. This test reported back with a 359 and a green OK LED. The 359 represents the measured DIN during the test. As with the previous test vehicle, we started the engine and ran it at 2,000 rpm for about 15 seconds. It came back with 10.45V for the starter voltage and 14.42 for the alternator. For space considerations, I won’t show those pictures.
The next battery is rated at 850 CCA. Unfortunately, this battery is located under the passenger seat, so getting a rating was a mild inconvenience. Don’t be surprised to find this. Over time, you’ll become accustomed to knowing how to get to the battery. For vehicles like this, go to the remote battery posts for the tests (Figure 12). I went through the setup (as before) by holding the test button while connecting the tester. Pressing the “Up” arrow, I scrolled from the previous DIN setting to CCA. And like the first vehicle settings, the tool has either 840 or 860 CCA. I set the tester to 860 and made the test. It returned with 613, a green “OK” LED, and a yellow “Low” LED (Figure 13). This means that it considers the battery in good shape but low on voltage. Charge the battery, and then continue with the remainder of the voltage tests. If the conductance test had returned with just the yellow LED, the tester is unsure of the battery’s condition. A result like this is likely on a vehicle that’s sat for a long time. The battery could be okay, but it’s just low on charge. A traditional load test would fail this battery, so it’s not a bad result. If you don’t get a solid green after fully charging the battery, replace it. But remember, if the battery is overcharged, you’ll get a RED failure. That was the case with this test vehicle after charging the battery. Once I got the voltage around 12.6, it passed.
The conductance test is an easy and comprehensive way to test the condition of a battery. If you decide to get a conductance battery tester, there are many manufacturers and models to choose from, so take your time checking the features. The beauty of using this type of battery tester is that an entry-level person can do the tests as part of the initial inspection. Discovering a bad battery before going through repair can save you some grief and your customer some money.
Editor’s note: ATRA will conduct several live electrical training sessions on the Friday before Saturday seminars. Check the schedule to see if there’s one at your seminar.
1 Vince Fischelli, founder of Veejer Enterprises developed a testing manual called, First Things First. It’s available, along with other training materials, at https://training.veejer. com. Understanding these testing principles is a must for properly diagnosing modern electronics systems.
