Gale Kimbrough, Technical Services Manager
Many years ago, a vehicle’s cranking cycle demanded a longer duration (five to 30 seconds) due to non-electronic ignition systems and carbureted engines. Some carbureted engines required multiple accelerator hits prior to cranking, while others required only one depression. Some of the air-flaps on the carburetor would not close while others would always close. Once the vehicle started, there were minimal electrical/electronic accessories to operate, and virtually no key-off drain to discharge the battery overnight. Under-hood temperatures were lower, and the battery didn’t operate as hot (in high-heat areas) compared with many of today’s vehicles.
Depending on the amount of years we go back, the engine oils could have been straight weights like 30 WT, and when it got cold, the engine oil lubricated much slower due to thickness. We were dealing with engines that were known by the cubic inch displacement (CID) such as 283, 302, 327, 289, 402, 427 and 454.
The battery, of which there were only a handful of choices, under the hood was a lead-acid battery, and in the early 1980s, most V/8 Chevy engines had an OE CCA requirement of 350 CCA, so the battery didn’t require many plates per cell. Most of the auto batteries came with lead antimony positive and negative plates. The vehicle’s charging systems were typically regulated to or around 13.8 V to 14.0 V, which was consistent with the lead antimony charging needs of the battery. Battery manufacturing processes at that time were dedicated to a lot more manual labor, and the lead plates were typically overbuilt for the application. If the alternator belt broke or the charging system encountered a malfunction, the reserve capacity minute rating would allow the vehicle’s engine to continue running until the lights started to dim.
In that era, we primarily lived in a “do-it-myself” world of maintenance necessary for our vehicles, which included batteries. As previously mentioned, the batteries were primarily lead antimony, and a significant amount of gas evolution was present around the battery. Some were coming on the scene with lead calcium positive and negatives that reduced the gassing level. Battery maintenance was necessary to keep the cable connections clean, as well as to reimburse the evaporated water in the battery.
The BCI manual offered us information stating that 2.11 volts per cell (12.66 V) and 1.265 specific gravity was a fully charged battery. It was also noted that there was only one sanctioned method of testing, which included applying a load of half of battery-rated CCA for 15 seconds only after ensuring the battery was 75 percent or more charged prior to load testing.
What about those other lead-acid batteries like Gell and AGM? Obviously, they were around but primarily used in applications other than automotive starting.
Batteries for almost all applications underwent a lot of changes in the middle to late 1980s, 1990s and now the first few years of the 2000s. Many in auto/commercial starting applications transitioned from antimony (high percent) to low percent on the positive and lead calcium negative to a lead calcium for both positive and negative plates. Along the way, we saw variances or nuances like lead calcium with silver on the positive, additions of sodium sulfate, heat-related changes to the negative plates, as well as expanded metals for one or both plates. The processes continue to evolve to different manufacturing processes, like using a continuous roll of lead material and a high-speed stamping process along with rolling methods to gain strict and precise thickness levels.
Today’s Vehicle and Battery
So many changes have evolved in a few decades. Many of today’s engines start in 750 milliseconds to two seconds due to precise electronic fuel injection processes. The OE CCA amp requirement for starting vehicles has generally climbed to 100 to 150 more than in 1980, but for a much shorter duration. The charging system voltage regulation on many vehicles still hovers around 14.0 V to 14.5 V for 12-volt systems. However, electrical/electronic demands have multiplied. Under-hood temperatures have skyrocketed in recent years, and the under-hood battery reflects the temperature increase. Recent data collection illustrates that in extreme hot climate situations, the battery is placed into an under-hood environment of 140°F (60°C) to 195 (90°+C), slightly different circumstances than in the 1980s. Battery key-off drains (parasitic draw in milli-amps) have also increased due to the number of computer processors keep-alive parasitics per vehicle, as well as the many add-on electronic accessories used. With these parasitics and the increased heat, under-hood has changed how the battery fails and why.
Government regulations continue to place stringent fuel mileage and environmental standards for today and tomorrow. Let’s circumvent the nickel-based or lithium-based batteries for hybrids and focus on continuing looking at lead-acid and its role for a few more years.
Future starting cycles should be the same or slightly less in duration (milliseconds) but will be more numerous due to automatic-engine-off at idle concepts. Start/stop concept: Each time the vehicle comes to a stop sign or red light, the engine shuts down, creating a potential for vehicles with higher average fuel mileage vehicles. There is also an increased demand for additional electronic control modules, which increase safety when we can’t or don’t make the correct decisions or are impaired behind the wheel. So will that battery be a single lead-acid battery that can produce additional medium or deep cycles and can support tens of thousands of additional starts each year? If so, it will need to be a super-flooded lead-acid or, more than likely, an AGM super battery. This AGM will require a super recharge acceptance in comparison to older technology. The internal impedance or resistance value will require it to have almost a starting-capacitor-like resistance to produce millisecond power and super recharge acceptance, yet also two-in-one battery capability to carry the increased power loads with the vehicle off multiple times per day. This will require this battery to have medium- to deep-cycle characteristics, also. OK, maybe we need more than one battery. However, the technology exists now where this could be contained in one lead-acid battery.
One battery discharge plus one recharge is considered a battery cycle. The percentage of the battery’s capacity discharge in amps and time compared with the battery’s capacity determines whether it’s a shallow, medium or deep cycle. For example, a 100-ampere-hour-capacity battery is discharged by 5 amps for six hours. This would approximately equal a discharge of 30 AHS, or 30 percent depth of discharge.
Once a vehicle is engaged in a starting cycle, the battery slams into action and produces several hundred amps of power immediately. We typically rate that battery action in CCA (cold cranking amps) at 0°F (-18°C) for 30 seconds. Once the vehicle starts and the charging system engages, the battery is generally reinstated within minutes of normal driving. One starting cycle is complete. Due to the short amount of time of an engine start, this is normally considered a shallow cycle because even though it requires a lot of amps, it is such a short duration that only a single-digit percentage of capacity is used.
If or when the vehicle is idling or shut off, the battery now takes on additional responsibilities to power-share or serve as the single source of power. Considering a start/stop action where the battery may be supplying multiple minutes of power with no or minimal recharge, an increased percentage of the battery’s capacity is used. This is a cycle that can be from 10 percent depth of discharge to maybe 25 to 30 percent depth of discharge level. The deeper the depth of discharge of a starting battery, the less overall life expectation. Typically, a lot less.
Deep-cycle batteries are used in applications like marine/RV auxiliary batteries to run house loads. A vehicle key-off drain that allows the battery to discharge to a high percentage of its capacity (30 percent or more) is considered a deep cycle, but this would most likely be an anomaly due to a defective component or operator error (like leaving the lights on or running the accessories too long).
The 1980s are Gone
Vehicle demands have changed, and so have the vehicles – including emissions, fuel mileage, safety features, navigational systems and vehicle creature comforts that we have gotten very accustom to using.
We still have a CCA rating at 0°F for 30 seconds without falling below 7.2 volts that was used in the 1980s. We continue to have a reserve capacity rating on a starting battery to see how many minutes it can produce or discharge at 25 amps at 80°F.
Do those ratings and standards still fit the vehicle starting battery of today and tomorrow? Do we need to have a 30 percent DOD tests for auto starting batteries used in today and tomorrow’s vehicles?
Do we need a battery than can produce 50,000 starts and 1,500 30 percent depth-of-discharge cycles all in one battery for start/stop applications? Will cyclability be labeled on the battery? Can lead-acid batteries continue to produce the requirements we have created? Is there room to design a porosity/density on the paste to affect major battery needs going forward? In my humble opinion, yes.
Gale Kimbrough manages the battery engineering and testing lab at Interstate Batteries in Dallas. Through more than 25 years’ experience of battery tear-down analysis, he has extensive knowledge of how batteries are manufactured and how they perform in any atmospheric and environmental setting. He has written hundreds of articles pertaining to automotive maintenance, specializing in batteries and the vehicle’s electrical/electronic system. He is the co-writer of Interstate Batteries’ technical manual, which is used by various associations as study guides for electrical testing. His specialty is taking the difficult technical aspects and simplifying them for the consumer.
For more information, please visit www.interstatebatteries.com.