The Specs: A Breakdown of Automotive Batteries

Dec 2, 2016


Vehicles give off multiple signs when it’s time to replace the battery under the hood. Slow engine crank, check engine light, and swelling of the battery case are a few of the most common signs. When it is time to replace the battery, be aware of the different replacement options out there. There are three common types of batteries: Wet Cell, VRLA, and Lithium-Ion. 

1. Wet Cell or Lead Acid is the traditional maintenance-free battery. Lead acid batteries retain their fluid for the life of the vehicle. One downside to a lead acid battery is that it doesn’t hold a charge for as long as a VRLA battery. But lead acid batteries are typically cheaper than other types of batteries. 

  • Most vehicles are outfitted with a Starting, Lighting, and Ignition (SLI) battery from the factory, which is a type of lead acid battery. These batteries use short bursts of energy to start the starter motor, lights, and the ignition system of a vehicle’s engine. SLI batteries do not hold charge as well as VRLA batteries, but they are much more affordable. 

2. Valve-regulated lead acid batteries (VRLA) are typically used in luxury vehicles such as BMWs and Land Rovers. The VRLA is a sealed battery that does not allow any venting of gasses. They are also known for storing well because they do not degrade easily. Since these batteries don’t leak or release any hydrogen gas, fluid loss is prevented. The VRLA battery is also considered to be the safest battery. Keep in mind that VRLA batteries are unserviceable due to the fact that they are completely sealed. A VRLA battery is typically more expensive than the affordable SLI battery. The two main designs of the VRLA battery are the GEL and AGM. 

  • Gel cell batteries use silicon to make the interior gel-like as opposed to the regular battery acid that SLI batteries are made with. Since gel batteries are completely sealed, it is next to impossible for any battery acid gel spillage to occur. Gel batteries can withstand extreme temperatures and they hold charge better than SLI batteries. Gel batteries are not charged like SLI batteries. They charge at a slower rate and cannot be fast-charged on automotive chargers. Other than a handful of vehicles such as the Mazda Miata, vehicles are not typically outfitted with gel cell batteries.
  • Absorbed Glass Mat Batteries (AGM) are becoming increasingly popular due to the need for more power for features such as stop-start systems and power outlets for mobile electronics, as well as their superior performance compared to gel cell and SLI batteries. AGM batteries use fiberglass separators to keep the electrolytes between the lead plates. AGM batteries withstand repeated draining and recharging cycles, so they are a good choice for non-daily-driver vehicles. They also resist freezing for longer than conventional batteries, so it’s less likely that you’ll need to recharge the battery in the dead of winter. Sports cars and luxury vehicles are typically outfitted with AGM batteries.

3. Lithium-Ion Batteries are typically used in electronic vehicles as well as in consumer electronics such as laptops and cell phones. They have a higher energy per unit mass compared to other electric energy storage systems. They also have a high power-to-weight ratio which makes them lighter than typical car batteries which results in better performance and more mileage per charge. Lithium-Ion batteries are also recyclable and considered much better for the environment than batteries that power non-electric vehicles.


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