How automotive battery needs are changing
A few years ago, a vehicle’s cranking cycle demanded a longer duration (5-15 seconds). Carbureted engines would often require multiple hits of the accelerator to get things started.
Once you started the vehicle, there were only a few electronic accessories that needed to draw power, and there was virtually nothing to drain the battery when the key was off. Under-hood temperatures were lower, and the battery didn’t operate as hot (in high-heat areas) compared to many of today’s vehicles.
Depending on the amount of years we go back, the engine oils could have been straight weights like 30wt, and when it got cold, the engine oil lubricated much slower due to thickness.
Today’s vehicles are much more technologically advanced. Many of today’s engines start in 750 milliseconds to two seconds, thanks to electronic ignition systems. But the other demands on the battery have multiplied. Under-hood temperatures have skyrocketed in recent years. Battery key-off drains (parasitic draw in milliamps) have also increased due to the number of computer processors per vehicle electronic accessories used (see Chart 1).
Future starting cycles should be the same or slightly less in duration (milliseconds), but they’ll be more frequent thanks to start-stop or micro-hybrid technology that will find its way into the mainstream. In a micro-hybrid, each time the vehicle comes to a stop sign or red light, the engine shuts down. This creates better fuel mileage, but it increases the demands on the battery. Additional electronic gadgets and control modules will also demand more for the battery, causing it to cycle deeper (see Chart 2).
One battery discharge plus one recharge is considered a battery cycle. The percentage of battery discharge in amps and time compared to the battery’s capacity determines whether it’s a shallow, medium or deep cycle(see Chart 3).
Once a vehicle is started, the battery slams into action and produces several hundred amps of power immediately. We rate that battery action in CCA (Cold Cranking Amps). Once the charging system engages and the battery is recharged within 3-6 minutes of normal driving, one starting cycle is complete. Due to the short amount of time of an engine start, this is called a shallow cycle.
When the vehicle is idling or shut off, the battery now takes on additional responsibilities to either share or serve as the single source of power. We rate this action in RC (Reserve Capacity). Because the battery is discharged deeper than a shallow cycle, this is termed a medium cycle.
Deep Cycle batteries are typically 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 (50% or more) is considered a deep cycle. For an automotive battery, 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.
Batteries for Today and Tomorrow
Let’s recap the three key areas of responsibility for today and tomorrow’s starting battery:
- CCA that meets manufacturer requirements
- RC that assists in discharge
- The number of various cycles to meet demands
A quality starting battery can produce thousands of shallow start cycles, a hundred or so medium cycles, and 20-30 deep cycles. If the battery is used to start only, you’ll probably get several years of starts . When the starting battery has to endure multiple medium and deep cycles, the number of starts is reduced dramatically.
Tomorrow’s vehicle usage, starts and stops plus the increased number of accessories, will determine how batteries should be enhanced to accommodate deeper discharge requirements while providing increased starts.
Interstate’s entire team is not only devoted to determining the battery requirements of today and tomorrow’s vehicles, but also testing and validating their capability in CCA, RC and cycle ability.
Learn about the new Interstate MT7 AGM battery designed for high accessory-load vehicles.