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Choosing Group 34/78 Battery for Car

Choosing an AGM-Batterie Group 34/78? In this article, we’ve selected the best Group 34/78 car batteries.

Group 34/78 batteries are used for GM pickups, SUVs, and midsized and large sedans. AGM batteries can work even in the most difficult conditions and last much longer than conventional lead-acid batteries.

What are the 34 / 78 batteries?

Batteries 34 refer to batteries of certain sizes with top leads. Battery 78 also refers to a certain size battery with side terminals. The physical dimensions of the two 34 and 78 batteries, at least relative to their size without terminals, have been found to be identical. As a result, 34/78 batteries, which have the same physical size, may have both top and side terminals,

AGM 34 batteries indicate top terminals and 78 batteries indicate side terminals. Now there are some applications where a group 78 battery will fit, but not a group 34 or group 34/78, because of height clearance issues with the top terminals.

There are two types of batteries: lead-acid and glass mat (AGM). Lead-acid batteries are outdated technology – you no longer need to refill them with distilled water – while AGM batteries are modern and suitable for cars with more advanced electrical systems.

The best brands of 34/78 batteries

  • Optima REDTOP Batteries
  • Delphi MaxStart AGM
  • ACDelco Professional AGM
  • Optima YELLOWTOP Batteries
  • Odyssey Extreme Series

Best AGM Batteries 50Ah Group 34/78

Optima Batteries 8004-003 34/78 RedTop Starting Battery

Optima Batteries 8004-003 34/78 RedTop Starting Battery


  • Rating: 4,4 ∗∗∗∗∗
  • 12-Volt, 800 Cold Cranking Amps
  • Reserve capacity of 100 minutes for constant performance

Optima Batteries OPT8014-045 8014-045 D34/78

Optima Batteries OPT8014-045 8014-045 D34/78


  • Rating: 4,4 ∗∗∗∗∗
  • 12-Volt, 750 Cold Cranking Amps
  • Reserve capacity of 120 minutes for constant performance

Best AGM Battery 44Ah Group 34/78

Optima Batteries OPT8022-091 8022-091 75/25 Starting Battery

Optima Batteries OPT8022-091 8022-091 75/25


  • Rating: 4,4 ∗∗∗∗∗
  • 12-Volt, 720 Cold Cranking Amps.
  • Reserve capacity of 90 minutes for constant performance.

Best AGM Batteries 55Ah Group 34/78

Optima Batteries OPT8014-045 8014-045 D34/78

Optima Batteries OPT8014-045 8014-045 D34/78


  • Rating: 4,4 ∗∗∗∗∗
  • 12-Volt, 750 Cold Cranking Amps.
  • Reserve capacity of 120 minutes for constant performance.

Delphi BU9078 MaxStart AGM Battery Group 78

Delphi BU9078 MaxStart AGM Battery Group 78


  • Rating: 4,0 ∗∗∗∗∗
  • 775 CCA (cold cranking amps) and 120 R.C. (reverse capacity).
  • 20x the vibration resistance of conventional batteries.

Best AGM Battery 60Ah Group 34/78

ACDelco 78AGM Professional Battery Group 78

ACDelco 78AGM Professional Battery Group 78


  • Rating: 4,0 ∗∗∗∗∗
  • Voltage:12 V.
  • 100% leak and spillproof.

Best AGM Batteries 68Ah Group 34/78

Odyssey 34/78-PC1500DT Automotive and LTV Battery

Odyssey 34/78-PC1500DT Automotive and LTV Battery


  • Rating: 4,4 ∗∗∗∗∗
  • Cold Crank Amp (CCA)- 850.
  • 70 Percent Longer Cycle Than Conventional Deep Cyc. Batteries.

ODYSSEY Batteries 78 PC1500-A Automotive/Light Truck and Van Battery

ODYSSEY Batteries 78 PC1500-A Automotive/Light Truck and Van Battery


  • Rating: 4,5∗∗∗∗∗
  • 12-Volt, Cold Cranking Amps: 880.
  • Faster recharge.

What is an AGM battery?

The AGM battery is especially suitable for vehicles with an auto-start and stops function.

The AGM battery is a modern type of car battery that is mainly used as a starter battery in cars with a start-stop function. The AGM battery is often used as a power source for boats or mobile homes. The AGM battery is also used in the solar sector.

The importance of the AGM battery can be attributed to fiberglass construction. “AGM” stands for Absorbent Glass Mat. As a result, the special car battery has a long life and is largely sealed. In addition, there is no need to fill the AGM battery because there is no need to refill water. An AGM battery can be recognized by the corresponding label on the case.

In contrast to conventional lead-acid batteries, the so-called AGM-VRLA (valve-regulated lead-acid battery), AGM automotive batteries are very typically used in vehicles equipped with a so-called start-stop system. The engine automatically shuts off when the vehicle is stopped (e.g. at a traffic light). If the driver finally reengages the gearbox again, or the clutch starts the car again.

Below is an overview of the most important advantages and disadvantages of an automatic start-stop system:


  • The engine automatically shuts off when the vehicle is stationary.
  • Fuel savings of up to 15% (depending on the manufacturer)
  • Protects the environment
  • Highly recommended for city traffic


  • Virtually no effect on fuel consumption on long trips
  • Increased wear and tear is possible

Types of car batteries

Car batteries come in two main types: the more traditional, maintenance-free batteries and the more advanced absorbent glass mat (AGM) batteries.

Lead-acid (conventional)

Batteries once required drivers to periodically refill water into the electrolyte solution, the liquid inside being the battery’s power source. Today’s maintenance-free batteries consume much less water than traditional batteries with flooded cells. Maintenance-free batteries retain their fluid for the life of the battery, and the covers on these models are not designed to be removed. There are still batteries that can be topped up with distilled water; with proper care, they can last longer in hot climates.

A lead-acid battery will usually cost much less than an absorbent glass mat battery. However, it will not hold a charge as long and will tolerate a deep discharge worse.

Absorbed Glass Mat (AGM)

AGMs can withstand repeated discharge and recharge cycles better than standard batteries. They are becoming standard equipment in more cars because modern features such as fuel-efficient stop-and-start systems, electronic safety and convenience features, and outlets for mobile electronics all increase energy demand.

But AGMs can cost 40 to 100 percent more than conventional, highly rated batteries. Consider buying one if you sometimes don’t use your car for long periods of time and the battery runs out. An AGM battery is better able to withstand a deep discharge and is more likely to fully recover if it accidentally runs out of power.


  • Has low self-discharge
  • long life
  • insensitive to cold


  • often expensive to buy
  • prone to high temperatures

Group 34/78 Batteries of Features

Group 34 batteries are medium-large, but still, rather powerful batteries, featuring 20h capacity in the 50-75 Ah range, providing 750-900 CCA, 100-145 minutes of Reserve Capacity, etc. Their weight depends on the chemistry, battery type, and internal construction, and it ranges between 37 and 51 pounds (16.8 – 23.1 kg).

BCI group 34 batteries are commonly used in automotive, marine, industrial, and off-the-grid applications in the form of starting, dual-purpose and deep cycle batteries, offering good starting/cranking characteristics, many charging/discharging cycles, and excellent deep cycle recovery – battery type-dependent, of course.

Group 34 Batteries and Group 34R Batteries

Generally speaking, the only difference between a Group 34 battery and a Group 34R battery is the orientation of the terminal blocks.

While Group 34 batteries have the positive terminal on the left, Group 34R batteries have the positive terminal on the right, hence the “R” after the “34”.

Most popular brands make their Group 34 batteries in both “34” and “34R” versions, so if “34R” models are required, they are not difficult to obtain even from online retailers.

Which Group 34/78 battery should I buy for my car?

The main parameters of the battery are:

  • Date of manufacture of the battery
  • Starting current (cold start current);
  • Battery capacity (nominal and reserve);
  • The need for maintenance;
  • Design.

Date of manufacture of a Group 34/78 battery

The date is important due to the battery’s property of self-discharging. The battery loses its capacity during use. Therefore, you should buy a battery with the most recent date.

Starting current of a Group 34/78 battery

Cold start current characterizes the capacity of the battery in amperes. The physical meaning of this value, marked on the battery by a three-digit number is the energy the battery gives in 10 seconds when starting at 18 degrees below zero. The higher this value is, the better. But for a particular car, overpaying for too much current may be unnecessary. Diesel engines are the most sensitive to this parameter.

Battery capacity Group 34/78

A higher ampere-hour capacity is not always appropriate. The capacity should not be less than that of the base battery, perhaps a little more. Low capacity shortens the life of a lead-acid battery, leading to a deep discharge. In addition, as the charge drops, so does the terminal voltage, and thus the amperage as well. It is more difficult to start on a dead battery, especially in the cold. Reserve capacity in practice is measured in the minutes that the car can drive powered by the battery, without the alternator.

Selecting the battery by size

The battery must stand in its original place. The battery compartment differs from vehicle to vehicle. While European and domestic models allow for a little variation, in most Japanese cars these dimensions are severely limited.

When selecting an AGM-Batterie Group 34/78 in the car, you need to consider:

  • The length, width, and height of the battery;
  • Compatibility with the vehicle’s mounting mechanism;
  • The polarity of the battery (forward or reverse terminal arrangement).

Design and mounting of the Group 34/78 battery

The battery must fit the dimensions of the compartment in which it will be installed. While some cars have a backlash, others have minimal clearance. Once placed under the hood, the battery must be secured.

There are three types of fasteners – top clamping bar, two- or four-way clamping from the bottom. Well, and polarity: buy a battery for the car the correct polarity – means to save yourself the manipulation of the wires. Straight polarity: “+” and “-” from left to right, reverse – vice versa.

battery Group 34/78

By design, a distinction is made between low-maintenance liquid electrolyte batteries, maintenance-free AGM batteries, and gel batteries.

Labeling of Group 34/78 Batteries

The labeling of batteries for vehicles produced by different companies varies significantly, as do the batteries themselves.

Different vehicles have very different batteries, both in terms of their electrical characteristics and dimensions. Different countries have different requirements for technical information on batteries. Mandatory battery labeling requirements are described in several international standards.

Battery manufacturers themselves strive to put all the necessary information on the battery case:

  • The name and trademark of the manufacturer’s plant;
  • The marking of the nominal voltage of the battery;
  • Battery capacity value marking;
  • type of battery according to one or more international standards;
  • number of battery cells;
  • polarity marks of the battery terminals;
  • date of manufacture of the battery;
  • Warning marks for operation and transportation.

Battery sizes

Batteries come in a variety of sizes. It is important to choose the right one to ensure a secure fit and sufficient power. If the terminals are in the wrong location, your vehicle’s cables may not reach, or they will not fit securely. Refer to the store manual or setup guide. Many retailers will install the battery for free.

Size 24 / 24F (top terminal): fits many Acura, Honda, Infiniti, Lexus, Nissan and Toyota vehicles.

Size 34/78 (double terminal): fits many large Chrysler cars and many 1996-2000 GM pickups, SUVs, and midsize and large sedans.

Size 35 (upper terminal): fits most Japanese nameplates, including many recent Honda vehicles and most Nissan, Subaru and Toyota vehicles.

Size 47 (H5) (upper terminal): fits many Buick, Chevrolet, Fiat and Volkswagen models.

Size 48 (H6) (upper terminal): fits many European as well as American cars from Audi, BMW, Buick, Cadillac, Chevrolet, GMC, Jeep, Mercedes-Benz, Mini, Volkswagen and Volvo.

Size 49 (H8) (upper terminal): fits many European and Asian Audi, BMW, Hyundai and Mercedes-Benz vehicles.

Size 51R (upper terminal): fits many Japanese Honda, Mazda, and Nissan cars.

Size 65 (top terminal): suitable for large cars, trucks, and SUVs from Ford or Mercury.

Size 75 (side outlet): suitable for some General Motors midsize and compact cars and some Chrysler vehicles.

The best brands of AGM Batteries Group 34/78

There are many no-name brands available on the market that have no quality. The brand of the battery has a big impact on the overall quality of the battery. Make sure that you choose brand name models when buying an AGM battery. There are several well-known brands that guarantee quality. You will be able to use their product decisively.

These popular brands have earned a reputation for producing high-quality batteries that pair well with cars, SUVs, travel trailers and other types of vehicles. If you focus on reputable brands, you won’t have a problem choosing the best AGM battery because they usually use high-quality materials when manufacturing their batteries.

Proven battery manufacturers are: Optima, Delphi, ACDelco, ODYSSEY.

How do I replace the group 78 battery in my car?

Replacing a group 78 battery in a car is a simple task for most cars. You will only need a few simple tools such as a crescent wrench or a set of socket heads, a wire brush and some rags. Before you start, make sure the engine is off and the emergency brake is set. Lift the hood and use a holder to hold it in the raised position. You are now ready to get to work.

  • Remove the terminal connectors. Loosen the nut that secures the battery terminal connector to the negative terminal. Remove the terminal connectors from the pole. Now do the same with the positive terminal. Removing the negative terminal first will help avoid sparks;
  • Remove the battery mounting brackets. Then loosen the wing nuts or hex nuts on the battery bracket and remove it;
  • Remove the old battery. If the old battery has a strap or carrying handle, make sure they are in good condition before using them to lift the old battery from the tray. If not, carefully lift the battery from the bottom. Because of the possible ingress of battery acid, it is recommended that you wear gloves before proceeding with this method;
  • Inspect the battery tray holder. Next, carefully inspect the battery tray holder components, terminals, and wiring to make sure they are free of rust and in working order. If anything needs to be replaced, do so at this time;
  • Clean the tray holder and connectors. At this point, use a wire brush and a brush to remove rust and corrosion from the terminals, battery tray, and all components. Be sure to wipe everything down with a rag before proceeding;
  • Place the new battery into the battery holder. Lift up the battery and make sure it is flush with the bottom and does not move in the tray;
  • Secure the battery. Reinstall the four battery holder clamps and make sure the battery is securely fastened;
  • Reconnect the battery. Now it is time to reconnect the battery terminals in the same manner, starting with the negative terminal first;
  • Start the vehicle. Once everything is connected and secured, you can start the car to make sure everything is working properly.

AGM Battery Charging and Maintenance Instructions

Procedure for charging an AGM battery:

The battery can be charged at an optimum rate at the proper temperature. Consequently, room temperature is required to charge the battery quickly.

However, if it is too hot or too cold, it will take many hours to charge the AGM battery.

The optimal charging rate is 2.4 to 2.465 volts per cell. And the temperature should be around 25°C / 77°F.

The recharge rate also depends on the depth of discharge of the battery. You can’t just plug it in to charge when you want to. Each AGM battery has a different DoD number.

So, for example, if your battery has a DoD number of 60%, you need to use at least 60% or more before charging it.

Also, partially charging a battery is not good for this. You may lose the ability to recharge it to 100% at all.

So, you need to let your AGM battery reduce the required DoD rate and then fully charge it to keep it working perfectly.

AGM battery maintenance and care:

Now an AGM battery needs no maintenance, which is not wrong. But you do need to do certain things to extend its life.

For example, if you are not using the battery, store it in a cool place. Otherwise, its performance will decrease. And at least charge it every 4 months. Even if you don’t use it, the battery slowly drains energy. So, it needs to be refilled.

Battery sulfation is common with AGM batteries. To avoid this, you need to fully charge the battery before you put it away for storage. Follow these steps and your battery will last for years to come.

How do you know if you need a new car battery?

There may be signs that your car battery is running low. Excessive corrosion around the rack and cable connectors probably means acid leakage. Some cars will have a flashing “check engine light” if the battery is low, although in most cases you won’t know exactly what the light means without access to an OBD II scanner. An obvious crack, bulge, or war page on the battery case is a good indication that you should look for a new one.

However, the above conditions are relatively rare, and their absence does not necessarily mean that the battery is serviceable. Ten or 20 years ago, battery deterioration gradually manifested itself in one obvious way: increasingly slow and difficult engine starting or starting, especially during cold weather. Some recently manufactured batteries may still behave this way, but most modern batteries will continue to start normally until they no longer crank.

Modern batteries generally continue to turn momentarily until they no longer turn. A battery inspection is necessary. If your battery is 3 years old or older, have it checked annually. Many retailers will do this for free on the spot. It’s easy, and it’s the only way to be sure.

A car battery needs two things: cranking power and reserve capacity. Cranking capacity is essentially the large electrical discharge needed to start the engine. It is measured as the cold start current, or CCA, or the number of nearly instantaneous amps the battery can deliver at 0 degrees Fahrenheit. Reserve capacity accounts for the smaller and slower flow of electricity to power devices such as lights or radios when the car is off and the battery is not charging. This is measured in ampere-hours or Ah of total stored energy, and sometimes in minutes – how long the battery will provide power at a certain rate of discharge. Manufacturers evaluate their own batteries, and lab tests have shown that in real-world conditions, batteries sometimes don’t meet the manufacturer’s claim.

Nevertheless, the two requirements for a 12-volt car battery can work in different directions. A battery with enough starting power to start a cruise liner will not necessarily keep the headlights on for 20 or 30 minutes. All automotive batteries are a compromise in this balance of cold start booster power and reserve capacity, and much of the technological development of lead-acid batteries has been aimed at improving this balance.

How to Charge Group 34/78 and Group 78 Batteries?

When the battery is connected to the car’s electric system, it is being charged and monitored by the very same car’s electric system – when the car’s engine is ON, the alternator produces electricity and the part of the electricity is used for recharging the battery.

If there is an issue with the alternator and/or battery, the car’s electric system will notify the user – most modern cars will display an error message of some kind (code or detailed text, car-dependent).

However, batteries that are used in industrial applications should be charged using smart AGM battery chargers that can analyze the battery and adjust the charging process to the battery’s condition – desulphation and cell-equalization modes are very important for prolonging the operating time of such batteries.

For batteries in 60-70 Ah capacity range, advanced 10-15 Amps AGM battery chargers are recommended.


AGM batteries have a long life and last a long time. Just make sure that the battery is not discharged below 60%. Now, you have our picks for the Group 78 battery. Any of these choices are an excellent pick for most circumstances.

AGM Group 34/78 Batteries Price:

AGM Batteries Group 34/78 Under $300

  • Optima Batteries OPT8014-045 8014-045 D34/78
  • Optima Batteries 8004-003 34/78 RedTop Starting Battery
  • Delphi BU9078 MaxStart AGM Premium Automotive Battery
  • ACDelco 78AGM Professional AGM Automotive BCI Group 78 Battery

AGM Batteries Group 34/78 Under $400

  • Odyssey 34/78-PC1500DT Automotive and LTV Battery

AGM Batteries Group 34/78 Under $500

  • ODYSSEY Batteries 78 PC1500-A Automotive/Light Truck and Van Battery

FAQs about AGM Battery Group 34/78

✅ What does battery group size 34 78 mean?

The 34 number refers to a battery of specific dimensions with top terminals, while a 78 number also refers to a battery of specific dimensions with side terminals. The physical dimensions of these two batteries, at least relative to their size without terminals, happens to be identical.

✅ What car uses a 34 78 battery?

Fits many large Chrysler vehicles and many 1996 to 2000 GM pickups, SUVs, and midsized and large sedans.

✅ What is the difference between Group 31 and 34 batteries?

Their group 31 is a 96 AH battery and group 34 is a 62 AH battery. I might eventually add a solar panel to supplement this setup and provide additional power for other accessories/gadgets when camped for longer periods of time.

What is the Difference Between a 75/25 and 34/78 Battery? – Video

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Max Welder (rvneeded)

Max Welder (rvneeded)

Max Welder is a mechanic enthusiast. Currently, working at a small company. Experienced in electronics, car tools, and security systems. In his spare time, he writes articles for various blogs.

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