PASS/FAIL: BATTERY TESTING & SERVICE BY BOB PATTENGALE It remained pretty quiet on the battery front for many decades, with the familiar lead-acid battery keeping its place at the top of the heap. It s still the leader, but other battery types requiring updated testing and service techniques are gaining in popularity. December is upon us and the temperatures continue to drop. In some areas, the temperature will gradually change, but in others, the temperature can drastically change from mild to freezing and back to mild in a very short period of time. One thing we know for sure: Drastic temperature changes will put a vehicle battery under significant stress. For most vehicle owners, the battery is something that s out of sight, out of mind until it dies. We also know that vehicle batteries rarely fail at convenient times, and you might get blamed for not catching an impending failure in advance. Repair shops are the first and really only line of defense that can detect a failing battery before it leaves the vehicle owner stranded. In real terms, depending on the vehicle owner s maintenance routine and the age of the vehicle, you might get only two opportu- Photoillustration: Harold A. Perry; images: Thinkstock 30 December 2012
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PASS/FAIL: BATTERY TESTING & SERVICE Internal Combustion Engine Idle-Stop Mild & Full Hybrid Electric Vehicle Plug-In Electric Vehicle Lead-Acid AGM Nickel-Metal Hydride & Lithium-Ion Lithium-Ion Fig. 1 These are the types of batteries in use today in various classes of vehicles. Even though hybrid and electric vehicles are gaining in popularity, a variation of the original lead-acid battery is still used in 93% of vehicles on the road. nities per year to check the battery, which it why it s so important to check the battery and charging and starting systems every time the vehicle is in the shop. Invented in 1859, the lead-acid battery is the oldest type of rechargeable battery and the most recycled part on a vehicle today. The overwhelming majority (93%) of the vehicles on the road today use a variation of the original lead-acid battery. If you take into account there are approximately 240 million cars and light trucks now on the road, with an average age of 10.8 years, the opportunity for a battery failure is fairly high. Approximately 125 million new vehicle and replacement batteries are sold per year. Battery technology is slowly evolving, but most of the changes today are related to alternative-fuel vehicles. Fig. 1 above shows where commonly used batteries are used on vehicles today. Let s take a quick look at each battery group: Lead-Acid. The lead-acid battery has evolved from a high-maintenance item to one that s 100% maintenancefree, with the use of different materials and design concepts. Maintenance-free does not mean it should be forgotten until it fails; it simply means you don t need to pull caps to check electrolyte The first step in testing a battery should be a visual inspection. Battery cables exhibiting this much corrosion should be cleaned prior to any testing. Photo: Bob Pattengale and specific gravity levels. But maintenance-free batteries should be visually inspected and tested on a regular basis. Absorbed Glass Mat (AGM). AGM batteries with electrolyte bound in fiberglass mats are used where greater demands are placed on the vehicle battery. AGM batteries can also be recycled and currently represent about 4% of the batteries sold. Some estimate that 25% of new vehicles produced in 2014 will be equipped with AGM batteries, increasing to 40% in 2016. The reason for this increase relates to idle-stop technology being rapidly introduced as a way to improve fuel economy and lower vehicle emissions. AGM batteries can handle three to four times the number of discharge/charge cycles as conventional lead-acid batteries, accept higher charge rates, operate in lower states of charge and provide higher cranking performance, all of which are essential for the new idle-stop systems. What is idle-stop technology? One way to save fuel and reduce tailpipe emissions is to turn the vehicle s internal combustion engine off when sitting at stoplights. This could be accomplished by simply turning the ignition key off, but that s not very practical and would put an added strain on a battery and charging/starting system designed for a much smaller number of starts. Idle-stop-equipped vehicles will handle this automatically by monitoring the wheel speed sensors and other systems to determine if the situation is right for an idle-stop event. Idle-stop-equipped vehicles will 32 December 2012
PASS/FAIL: BATTERY TESTING & SERVICE need new and more robust components. For example, in addition to an AGM battery, the starter will need to handle more than 400,000 starts. The starter pinion and ring gear will need to be strengthened, the alternator will need to be improved to provide quick recharge between stops and an electrical energy management system would be needed to determine if the battery is too depleted to handle the next idlestop event. Idle-stop is a simple alternative hybrid technology that can be implemented at minimal cost. Some estimates forecast an 8% increase in fuel economy, which is why we ll see this technology added as quickly as possible to most internal combustion engine vehicles. Nickel-Metal Hydride (NiMH) and Lithium-Ion (Li-ion). These and other batteries currently in development are primarily designed for hybrid and electric vehicles and represent a very small percentage of the vehicle batteries in use out there. Only highly trained technicians should be involved in testing and servicing these high-voltage batteries. However, most hybrid vehicles A variety of battery testers using the Midtronics conductance testing method are available, in a range of prices. All will provide accurate results based on the information provided, but a more expensive tester, like the Bosch BAT-151 shown here, will provide a more detailed analysis of the battery s condition. have a secondary lead-acid or AGM battery, which is used to power the immobilizer and other related accessory items that need to run independent of the high-voltage battery, and these secondary batteries should be Fig. 2 These printouts show the results after a battery was tested using a battery tester with a three-dimensional conductance testing format. The printouts provide a wealth of information about battery condition. Photo courtesy Robert Bosch LLC checked every time such a vehicle is in for service. The rest of this article will focus on testing and servicing lead-acid and AGM batteries. Always follow the vehicle and equipment manufacturers recommendations prior to testing and servicing the battery and charging/starting system. The first step, of course, should always be a visual inspection of the battery. Since everything in the electrical system depends on the battery and connections at the battery, I m always amazed that this is often overlooked during routine vehicle maintenance. No-start issues will be obvious, but a vehicle with an inferior battery or poor battery connections might be the cause of weird electrical system issues and driveability concerns. No driveability or electrical diagnosis should begin without checking the condition of the battery and its connections. The photo on page 32 shows a battery that should have the cables cleaned prior to testing. Corrosion at the battery connections will lead to inaccurate test results. If a customer complaint relates to a battery or the charging/starting system, make sure the correct battery is installed in the vehicle. In many cases when a battery fails, the recommended exact-match battery may not be available, so a substitute will be installed to get the customer going. If the battery selected is smaller less cold cranking amps (CCA) than recommended, an overcharging issue may occur. If the battery selected has a higher CCA than recommended, an undercharging issue may occur. In either case, this may reduce the life of the battery and create other electrical issues. In the case of the starting system, a higher capacity battery may be the cause of a starter that fails prematurely or causes mechanical damage at the pinion or flywheel ring gear. The next step is testing the battery to determine its state of charge (SOC) and state of health (SOH). In the early days of high-maintenance batteries, determining SOC would begin with removing the battery caps, checking the water level, using a battery hydrometer 34 December 2012
Photos: Bob Pattengale More expensive battery testers include additional functions, designed to other parts of the charging and starting systems. By connecting its leads at the starter and battery, this tester is being used to perform a series of Cable Drop Tests. These tests quickly pinpoint voltage drop issues within the electrical system, which may be responsible for starting and charging problems. to check the specific gravity of the electrolyte in each cell and using a voltmeter to check overall battery voltage or individual cells for variations between cells. Most maintenance-free batteries do not allow access to the cells for checking the specific gravity, but many battery manufacturers have added a visual indicator as a quick way to determine a battery s SOC. If the visual indicator has no color or is light yellow, it indicates the charge is low, and caution should be taken before testing or charging a battery in this condition. State of health would be checked using a manual load testing device with a carbon pile to simulate vehicle electrical loads. This early process was time-consuming and created some potential safety and vehicle damage risks from contact with battery acid. There would also be potential battery explosion issues during the load test portion of the test. A key point when using the manual load testing method is if the battery does not pass the SOC for safety reasons, you should not proceed to the SOH check. As vehicle technologies evolve, the methods of testing systems and components also change. That s certainly the Fig. 3 case with battery and charging/starting system testing. Conductance is an electrical measurement that determines the ability of a battery to transmit current through its internal structure. Midtronics pioneered conductance technology for battery testing, and it s at the heart of virtually every battery analyzer in use today. In conductance testing, a low-frequen - cy AC signal is sent through the battery. A portion of the AC current re- Conductance Cable Verification Test Technology C 2 Battery DUT D 2 D 1 Cable #2 Cable #1 R 1 R 2 C 1 December 2012 35
PASS/FAIL: BATTERY TESTING & SERVICE sponse is captured, and from this output a conductance measurement is calculated. Proprietary Midtronics algorithms utilize multiple conductance measurements, battery temperature assessments and voltage responses to provide a detailed picture of a battery s performance capabilities. The analysis can also track battery life and predict when the battery is nearing the end of its life. Battery testers using the Midtronics conductance testing method are available in a wide price range (from approximately $250 to $2000). As with many other products, the more you spend, the more useful features you ll get. For example, more expensive battery testers may include a three-dimensional process i.e., voltage, conductance and temperature to obtain the more detailed analysis of the battery condition. It will be up to you to decide which battery tester will suit your shop s needs. A low-priced tester typically will be designed to quickly test the battery and electrical system with minimal information and offer no ability to print test results. The first step after powering the tester is to select the style of battery to be tested. Selecting the flooded-wetcell or AGM battery icon will allow the tester to use the correct algorithm for accurate test results. As discussed earlier, most likely you re going to be testing a flooded-wet-cell style battery, but you should always visually inspect the battery to determine the type. If the battery is too difficult to access but you still want to perform the test, it s better to select the AGM option. The next step in the process is to select the temperature of the battery (not the ambient temperature). Battery temperature will vary based on how long it has been sitting or if the vehicle was recently started. In this case, the temperature reading has a very wide range, which is greater or less than 32 F (0 C). The yellow sun ball represents greater than 0 C and the snowflake represents lower than 0 C. The next step is common for all testers, which is to select the battery units (CCA, DIN, SAE, etc.) for testing. If the battery is hidden or the battery sticker is missing for some reason, you can use a battery catalog or look As battery design and construction continue to evolve, the process of charging batteries has changed. Different batteries require different charging rates. The AGM battery shown here was charged with a conventional battery charger, which cooked it. It s been cut apart to show the damage. It s going to be nearly impossible to avoid contact with AGMs, so make sure your shop has the proper equipment to test and charge them without inflicting preventable damage. up the information using your service information resource. After performing the test, the LEDs will display the condition of the battery. Green is good, yellow means it must be fully charged and retested and red means the battery should be replaced. If the battery checks GOOD, you can proceed to testing the charging and starting systems, which will use the live voltage reading to determine the quality of these systems. For example, if the voltage reading remains above 9.6 during cranking, the starting system passes the test. This is a very simple method of checking these systems. If you re using a more sophisticated battery tester, such as the Bosch BAT- 151 shown in the photo on page 34, many more questions will be asked during the selection process to determine the current condition of the battery prior to pushing the TEST button. For example, the tester may ask for the date code and whether the battery is a top-post, jump-start-post or sidepost. Then the temperature reading will be performed using the infrared temperature sensor on the bottom of the tester. If the Zip code is added in the shop information section, it will also be used to predict the life of the battery. Fig. 2 shows sample battery test results printouts from the BAT-151, which provides a wealth of information about the condition of the battery tested and what should happen next. The notes indicate the battery charge is low and should be recharged and retested. The entry AVG. LIFE IN AREA: 59 MO is based on the Zip code information provided. Here s another way to describe how different testers check the battery. The weatherman says the outside temperature is 70 F, but if he does not provide relative humidity, you really don t know how you ll feel when you go outside. The state of charge and the state of health of the battery are interrelated, but they re unique and fundamentally different measurements, just like temperature and humidity paint a more detailed picture of how you ll feel when you go outside. If the battery is fully charged as indicated by the SOC and the battery tests healthy re- 36 December 2012
garding the SOH, it gets a GOOD decision. If the battery is fully charged but the conductance is low (meaning the SOH is low), it gets a REPLACE decision. That s really all there is to it. In addition to the three-dimensional conductance battery test, a more expensive battery tester may use an amp probe to measure current during the charging/starting system test. An amp clamp provides the second measurement needed to truly understand the condition of these systems. Another advance feature offered by some battery testers is a Cable Drop Test, which uses conductance technology to send a signal through the circuit at the component under test. Fig. 3 on page 35 shows the simple electrical diagram with the Cable Drop Test connection points and the results of the test on an alternator circuit. The battery test leads (cable #1) are connected at the component output (B+ or output screw on alternator) and component housing as the ground. The DMM clamps (cable #2) are connected at the battery. The tester applies signals at all clamp positions and measures the response across the different parts of the circuit and at the battery. It then performs equations to remove the impedance due to the battery and calculates the impedance of the positive and negative cables. Using Ohm s law and an input cable capacity in amps, the tester calculates the voltage drop on the positive side, negative side and entire circuit. The voltage drop must be corrected for the charging system to operate properly. If any of the test results indicate that the battery needs to be charged before further testing, the correct battery charger must be used. So-called intelligent battery chargers have the ability to identify the type of battery to which they re connected, then adjust their output for efficient and safe battery charging. If you don t already have one, your shop needs to purchase an intelligent battery charger. End of story. New-technology batteries, including AGM batteries, must be charged with an intelligent battery charger to avoid battery damage. The photo on page 36 shows what can happen if a standard battery charger is used to charge an AGM battery. This mistake is not only expensive, but could be very dangerous. The bottom line is that 93% of the vehicles on the road today still use a variation of the original lead-acid battery and there are approximately 240 million cars and light trucks on the road today. Proactively testing batteries on every customer visit is always a good idea. This article can be found online at www.motormagazine.com. Circle #23 December 2012 37