ACDelco 78AGM Professional AGM Automotive Battery
Our 78AGM Professional AGM battery is engineered for drivers who demand starting power in extreme temperatures and accessory-heavy electrical systems. This absorbed glass mat battery delivers 750 cold cranking amps and fits Group Size 78 applications across GM vehicles and select imports.
The ACDelco 78AGM battery uses absorbed glass mat separators between the lead plates, which hold the electrolyte in a suspended state rather than free liquid. This construction allows the battery to recombine hydrogen and oxygen internally, eliminating the evaporation that requires periodic water top-ups in flooded batteries.
Fitment and Compatibility
Group Size 78 batteries fit a wide range of General Motors vehicles, including Chevrolet Silverado, GMC Sierra, Cadillac Escalade, and select Buick models from the 2000s onward. The 78AGM measures 10.94 inches long, 7 inches wide, and 7.5 inches tall, with top-post terminals arranged in standard GM polarity.
Before ordering, verify your vehicle’s battery group size in the owner’s manual or on the label of your current battery. The 78AGM uses the same footprint and terminal layout as the ACDelco 78 flooded battery, so it drops into the factory tray without modification. If your vehicle originally came with a flooded battery, upgrading to the 78AGM requires no special charging system changes — our AGM accepts charge from standard alternators.
Cold Cranking Amps and Reserve Capacity
We rate the 78AGM at 750 cold cranking amps, measured at 0 degrees Fahrenheit for 30 seconds while maintaining at least 7.2 volts. That power output ensures reliable starts in winter climates where flooded batteries lose significant capacity. The calcium-alloy grid structure reduces self-discharge, so the battery retains voltage during storage or infrequent use.
Reserve capacity measures how long the battery can sustain a 25-amp load before dropping to 10.5 volts. The 78AGM delivers 120 minutes of reserve capacity, giving you ample runtime if the alternator fails or you need to power accessories with the engine off. This metric is especially important for vehicles equipped with inverters, aftermarket lighting, or communication equipment that draw current during extended stops.
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Common Questions About the 78AGM Battery
The 78AGM is designed for four to six years of service life under normal driving conditions, depending on climate and electrical load. We back it with a 36-month free-replacement warranty. Extreme heat, frequent short trips, and deep discharge cycles can shorten lifespan, while highway driving and moderate temperatures extend it.
To maximize battery life, keep the terminals clean and ensure your alternator maintains proper charging voltage between 13.8 and 14.4 volts. If you store your vehicle for extended periods, connect a trickle charger to prevent self-discharge.
Yes, the valve-regulated sealed design allows safe mounting in any orientation except fully inverted. The absorbed glass mat holds the electrolyte in place, so the battery will not leak if installed sideways or at an angle.
This flexibility is especially useful for custom installations in RVs, boats, or vehicles with non-standard battery compartments. Just ensure the terminals are accessible for cable connections and that the case is properly secured to prevent movement during acceleration or rough roads.
The 78AGM fits most General Motors trucks and SUVs from 2000 onward, including Chevrolet Silverado, GMC Sierra, Cadillac Escalade, Chevrolet Tahoe, GMC Yukon, and Chevrolet Suburban. It also fits select Buick and Cadillac sedans with top-post Group 78 trays.
Some import vehicles, including certain Nissan Titan and Toyota Tundra models, also use Group 78 batteries. Always verify the group size and terminal orientation in your owner’s manual or by checking the label on your current battery before ordering.
No, the 78AGM accepts charge from standard automotive battery chargers and factory alternators. Set your charger to 10 amps or less and monitor voltage to avoid overcharging above 14.8 volts, which can damage the recombinant lid.
If your charger has an AGM or absorbed glass mat setting, use that mode for optimal charge acceptance. Avoid boost-charging or jump-starting at high amperage for extended periods, as AGM batteries are more sensitive to voltage spikes than flooded batteries.
The 78AGM uses absorbed glass mat separators that suspend the electrolyte in a gel-like state, while flooded batteries have liquid acid that can spill if tipped. AGM batteries tolerate deep discharge better, recharge faster, and never require water additions.
Flooded batteries cost less upfront but need periodic maintenance and lose capacity faster in extreme temperatures. The 78AGM delivers higher cold cranking amps and reserve capacity than a comparably sized flooded battery, making it a better choice for vehicles with high electrical demands or frequent short trips.
Signs of a failing battery include slow cranking, dimming headlights at idle, a battery warning light on the dashboard, or voltage below 12.4 volts after sitting overnight. You can test the battery with a digital multimeter or have it load-tested at an auto parts store.
If the battery is more than four years old and shows any of these symptoms, replacement is usually the safest option. AGM batteries often fail suddenly rather than gradually losing capacity like flooded batteries, so proactive replacement prevents being stranded.
Yes, the 78AGM is designed for vehicles with high electrical loads, including aftermarket stereos, winches, lighting, and inverters. The 120-minute reserve capacity provides sustained power when the engine is off, and the absorbed glass mat construction tolerates the deep discharge cycles that accessories create.
For extreme accessory loads or dual-battery setups, consider pairing the 78AGM with an isolator or battery management system to prevent over-discharging. The battery performs best when recharged to full voltage between use cycles rather than left in a partially discharged state for extended periods.