What AGM means
AGM stands for absorbent glass mat. In a regular, or flooded, battery the lead plates sit in liquid acid. In an AGM battery the acid is soaked into fiberglass mats pressed between the plates, and the case is sealed. Nothing sloshes and nothing gets topped off. It also handles repeated draining and recharging, and vibration, better than a regular battery does.
You can't always tell by looking. An AGM case is sealed with no removable caps, but some regular batteries are sealed too, so the label is what settles it.
Why some cars need one
A start-stop system shuts the engine off at a red light and restarts it when you lift off the brake. That asks a lot of a battery, which has to restart the engine many times in one drive and run the car while the engine is off. Cars with heavy electrical loads, or with systems that recover energy when braking, ask a lot too. Many of those cars come from the factory with an AGM battery.
A middle type called EFB, short for enhanced flooded battery, shows up in some start-stop cars with lighter demands. The rule for both is the same: replace what the car came with.
A start-stop battery works harder on every drive, and a Texas summer adds to that, so it is worth keeping an eye on as it ages.
How to tell what your car has
A few places will tell you:
- The label on the battery now in the car. It may say AGM, or VRLA, which stands for valve-regulated lead-acid.
- The battery section of the owner's manual.
- The dash. A car that shuts its engine off at stops almost certainly has an AGM or EFB battery.
- Dispatch. Give them the year, make and model, and the VIN if it is easy to reach.
Wrong type, right type
Putting a regular flooded battery into a car that came with AGM can go wrong. The charging system is set up for AGM, and in a start-stop car a regular battery tends to wear out far sooner than it should.
The other direction is usually fine. An AGM battery in a car that came with a regular one generally works, but you pay more for capability the car may not use. Some cars, mostly European makes, also expect a new battery to be registered with the car's computer so the charging system knows its type and age. Whether yours does is worth asking about before the old battery comes out.
The common mistake when buying a battery is to go by price and group size alone. Group size tells you it will sit in the tray. It doesn't tell you it suits the car.
Price and fit
AGM costs more than a regular battery, which is part of why battery pricing varies by vehicle and battery type. Battery replacement is $239–$255 for eligible vehicles and batteries, installation included, plus the $19 dispatch fee charged once per job. Tell dispatch your year, make and model, and whether the car has start-stop. Dispatch confirms the battery is compatible and tells you the total cost before a driver is sent.
Common questions
Not reliably. Look for AGM or VRLA printed on the label, or check the owner's manual. Don't guess from the shape of the case.
It is better at certain jobs, like repeated draining and recharging, vibration and start-stop use. In a plain older car, a regular battery does the work and costs less.
Yes. The jump itself works the same as it does on any other 12-volt battery.