Choosing the Best Deep Cycle Group 31 AGM Battery – Buyer’s Guide

A BCI Group 31 battery is a popular marine battery with an excellent starting power, but it is also used in cars, motorhomes, and other recreational vehicles. Some people replace their factory car battery with a Group 31 battery when upgrading the electronics. If you need a Group 31 battery replacement, the good news is you have many choices.

Group 31 Battery dimensions are: 13 x 6.8 x 9.4 inches, or 330 x 173 x 240 mm (Length x Width x Height).

This review explores some of the best Group 31 batteries available so you can choose the right one for your needs.

Best Choice

Banshee Deep-Cycle Dual-Purpose AGM Battery

The Best Group 31 Battery

This AGM battery has 700 CCA, 180 minutes of reserve capacity, and proven long-life in a sturdy, shock-resistant case. It recharges quickly and is rated for over 900 recharges at a 50% discharge depth. It is made for commercial vehicles with a lot of electronics used in big yachts and trucks. Banshee is recommended for boats, marine applications, and RVs, and it's an excellent choice for boats that only get seasonal use

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Quick Group 31 Battery Comparison Table

Image	Product
Best Choice	Banshee Group 31 Sealed AGM Deep Cycle Dual Purpose Marine Battery Cold Cranking Amps (CCA): 700, Reserve Capacity (RC): 180, Amp-Hours (AH): 105 Battery Group: 31 Type: AGM Warranty: 24 months Best Sealed Group 31 AGM Marine Battery Check Price	Check Price
Good Choice	NorthStar NSB-AGM31M AGM Group 31 Marine Battery Cold Cranking Amps (CCA): 1150, Reserve Capacity (RC): 220, Amp-Hours (AH): 103 Battery Group: 31 Type: AGM Warranty: 36 months Best for Fast Recharge Check Price	Check Price
Cheapest	Banshee 31 Series Marine Battery Replaces Blue Top D31M Cold Cranking Amps (CCA): 800, Reserve Capacity (RC): 190, Amp-Hours (AH): 105 Battery Group: 31 Type: Lead-Acid Warranty: 24 months Best Flooded Marine Battery Check Price	Check Price
Best Value	Optima Batteries 8052-161 D31M BlueTop Starting and Deep Cycle Battery Cold Cranking Amps (CCA): 900, Reserve Capacity (RC): 155, Amp-Hours (AH): 75 Battery Group: 31 Type: AGM Warranty: 36 months Best Dual-Purpose Group 31 Battery Check Price	Check Price
Maximum CCA	Odyssey 31-PC2150S Heavy Duty Commercial Battery Cold Cranking Amps (CCA): 1150, Reserve Capacity (RC): 205, Amp-Hours (AH): 100 Battery Group: 31 Type: AGM Warranty: 48 months Best for Stop/Start Technology Check Price	Check Price
Good Choice	Deka East Penn 8A31DTM Group 31 AGM HD Battery 12V 800CCA Cold Cranking Amps (CCA): 800, Reserve Capacity (RC): 210, Amp-Hours (AH): 105 Battery Group: 31 Type: AGM Warranty: 12 months Best Marine Cranking Amps Check Price	Check Price
Good Choice	Duracell Ultra Platinum AGM Deep Cycle Marine & RV Battery Cold Cranking Amps (CCA): 800, Amp-Hours (AH): 105 Battery Group: 31 Type: AGM Warranty: 18 months Best RV and Sump Pump Battery Check Price	Check Price
Good Choice	Deka East Penn 8G31DTM Group 31 AGM HD Battery 12V 550CCA Cold Cranking Amps (CCA): 550, Reserve Capacity (RC): 190, Amp-Hours (AH): 98 Battery Group: 31 Type: AGM Warranty: 12 months Best for Solar Power Check Price	Check Price
Maximum CCA	Odyssey 31M-PC2150ST-M TROLLING Thunder Marine Dual Purpose Battery Cold Cranking Amps (CCA): 1150, Reserve Capacity (RC): 205, Amp-Hours (AH): 100 Battery Group: 31 Type: AGM Warranty: 48 months Best Trolling Battery Check Price	Check Price
Good Choice	NorthStar ELT-AGM31 AGM Pure Lead Group 31 Battery Cold Cranking Amps (CCA): 925, Reserve Capacity (RC): 190, Amp-Hours (AH): 100 Battery Group: 31 Type: AGM Warranty: 36 months Best Heavy-Duty Commercial Battery Check Price	Check Price

Product Review

Batteries in 31 group vary in their specifications, more than many other battery groups. This can make choosing the right battery for your needs challenging. Now, let’s explore our top Group 31 battery picks.

1. Banshee Deep-Cycle Dual-Purpose AGM Battery — Best Sealed Group 31 AGM Marine Battery

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This Banshee battery is a rechargeable deep-cycle battery that uses sealed AGM technology. It's maintenance free, and you do not have to add water regularly. One thing that stands out is that it has a low self-discharge rate and can withstand long-term storage. This battery is recommended for boats, marine applications, and RVs, and it's an excellent choice for boats that only get seasonal use.

The battery has a low-pressure venting system and a high recovery rate to withstand deep-cycle charging and fast charging better than most. Banshee batteries use a unique design that controls the output of gas and allows recombination and recovery of over 90% of the gas generated. Its highly-efficient design is stable and reliable over time. The battery uses heavy-duty lead calcium-alloy grids that provide an extra boost of performance and extend the service life.

• Uses lead calcium-alloy plates

• Good for long-term storage

• Can be used with a fast charger

• Resilient under heavy use

• Low pressure venting system

• Gas recovery for efficiency

• Only has a 2-year warranty

2. NorthStar NSB-AGM31M Marine Battery — Best for Fast Recharge

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NorthStar batteries are known for their excellence in performance and proven long-life. This battery has excellent cold-cranking ability and a spill-proof design. It's rated for over 900 recharges at a 50% discharge depth. It also recharges quickly.

This battery has a fast discharge upon starting, which means that the engine will turn over quickly. It is also a good choice for engines that have a few miles on them, which might be more difficult to start. One thing to note is that this battery tends to have an excellent initial burst, but it then tends to drop voltage quickly. It is rated as a dual-purpose battery, but it's a better starting battery in actual use.

NorthStar batteries are always a good choice because they are so well made they can be transported as non-hazardous by ground, sea, or air. NorthStar has a state-of-the-art plant with excellent quality standards and consistency. This battery has a durable case and can withstand heavy vibration and shocks, making it a good choice for off-road and recreational vehicles.

• Suitable for older engines that are difficult to start

• Good for starting in cold weather

• Backed by excellent quality standards

• Long life at over 900 charge/discharge cycles

• Sturdy, shock-resistant case

• Voltage drops quickly after the initial starting burst

• Rated as dual-purpose, but better for starting

3. Banshee 31 series Marine Battery — Best Flooded Marine Battery

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This is the only flooded battery that made the list. It uses enhanced flooded technology intended for deep-cycle use. This battery is designed with dual terminals. It can be used on many fast chargers without damaging the battery, and it can also withstand many long, slow recharge cycles. This battery has a built-in hydrometer that lets you know how much battery life is left. You never have to worry about surprises, and you can have plenty of warning to get a new one before it leaves you stranded.

This battery is completely sealed, so you never have to add water. The Banshee 31 is recommended for its reliability and starting ability in any condition. Many people report long-lasting performance with this battery. This battery uses a unique flooded design uses thin-plate technology. Thin-plate batteries have 15% more surface area to allow better contact with the acid. This means better performance and power. The main reason why we recommend this battery is its resiliency. It can withstand over 400 charge and discharge cycles over its lifetime at 80% discharge.

• Reliable and resilient

• Long life

• Can tolerate fast charges

• Can’t be mounted on its side

• Uses flooded technology rather than AGM

4. Optima BlueTop 8052-161 D31M — Best Dual-Purpose Group 31 Battery

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The Optima BlueTop is designed for both starting and deep-cycle use. It has dual SAE posts made from stainless steel. This construction increases conductivity and resists the build-up of corrosion on the posts. Better conductivity means better starting in cold weather.

The Optima BlueTop is made to be resistant to vibration and shock. It has a tough outer case that will last for a long time. Optima batteries are produced under controlled environmental conditions to ensure quality and consistency.

Optima batteries are one of our favorites because their unique design leads to better performance and more power. This battery is meant to be used on boats and cars that have large electrical loads from accessories. Many people choose this battery for their RV because it can handle the loads of refrigerators, stoves, and other RV appliances. It is made to have a long-running time and is an excellent choice for trolling motors. The Optima BlueTop uses SpiralCell technology that improves conductivity and gives it a faster recharge time. It also has a durable case and can be mounted in any position, except upside-down.

• SpiralCell technology improves conductivity

• Stainless steel posts

• Durable case and good vibration resistance

• Suitable for RVs and boats with large accessory loads

• Long-running time

• Fast recharge

• Battery maintainer recommended for storage conditions.

5. Odyssey 31-PC2150S — Best for Stop/Start Technology

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Odyssey batteries are known as a battery heavy enough for commercial use. It has 1,150 cold-cranking amps and long service life. It has a 36-month warranty, but many people have reported that this battery can last for up to 10 years. Even if it does not last that long, it still has an exceptionally long reported lifespan, making it a good value. It's rated to withstand up to 400 cycles at 80 percent discharge while maintaining high levels of stable voltage under heavy use. Odyssey batteries also have a rapid recovery and charge quickly.

This is the perfect battery for heavy-duty use. It's made for commercial vehicles with heavy electronics use, including winches and high-power fog lamps. Its design makes it able to withstand long periods of idling in harsh climates. Odyssey makes its batteries with tightly packed, thin lead plates that allow up to 15% more contact surface area than SpiralCell technology. This gives it the ability to deliver more power and start reliably in the cold.

Odyssey is the brand of choice for emergency vehicles that must be reliable in any conditions. It has a high discharge rate for starting of up to 2,150 amperes for 5 seconds. It can maintain 1,750 amperes for up to 20 seconds, making it suitable for vehicles more challenging to start. Its terminals are corrosion-resistant, thin-plated brass made with a tight seal. This design allows the battery to recycle internally produced gases. It has a self-regulating relief valve for improved safety.

• Excellent design with a durable case

• Well-sealed, maintenance-free

• Excellent cold cranking amps for difficult starts

• Corrosion-resistant terminals

• Long battery life

• Weighs 77 pounds, heavy to lift

6. DEKA Intimidator 8A31DTM — Best Marine Cranking Amps

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The Deka Intimidator is the best-rated battery on the list for marine cranking amps (MCA). Marine cranking amps is different from cold-cranking amps (CCA) in that CCA reflects harsher conditions. Cold-cranking amps are tested at 0 °F (-18 C)°. To pass, the battery must not fall below 7.2 volts for 30 seconds. MCA is tested at 32 °F (0 °C). It is rare for a boat to be out in icy waters, but on newer outboards, many electronics must start at the same time, so the battery must have enough starting power.

Make sure to check the MCA rating in your boat manual before you choose your battery. This battery is the best one on the list for newer boats. It has a long life and is resistant to self-discharge, making it excellent for boats only used seasonally.

This battery is rated for its MCA, and it also has excellent CCA. It has a reserve capacity of 210 minutes. This battery is designed with dual terminals and includes both threaded and standard ones to be used in a wide range of vehicles.

• Best MCA battery

• Excellent for newer boats

• Good storage life

• Long reserve capacity

• Not the best for deep-cycle and trolling

7. Duracell Ultra — Best RV and Sump Pump Battery

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Duracell is a brand that might be more familiar in the consumer appliances and electronics category, but their recreational batteries also have a good reputation. One feature that Duracell prides itself on is the long life of its batteries. This battery is often used for sump pumps and RVs because of its excellent deep-cycle capabilities. It is designed as a marine battery, which means good in any weather and wet environments. It has excellent cold-cranking amps and can also handle long-term loads from electronics and other situations that require steady discharge.

Duracell designed this battery to be versatile and durable. It has a spill-proof design, which allows it to be installed on its side without worry. The AGM design of this battery makes it vibration-resistant and able to work in conditions that would be difficult for other batteries. It has a low self-discharge that makes it useful for camping and storage. Duracell included posts rated for DT, SAE/M8 Stud, SAE/M8 Threaded Post, and WNT, which creates a wide range of potential applications.

• Good for cold starts with 800 cold-cranking amps

• Suitable for wet areas such as basements

• Excellent choice for deep-cycle use

• Low self-discharge

• Good cold-cranking, but low compared to others on this list

• Balanced more towards deep-cycle use

8. Deka East Penn Dominator 8G31DTM — Best for Solar Power

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The Deka Dominator is rated for deep-cycle use. Many people choose this battery as a storage battery for solar power. It has excellent storage characteristics and is a perfect choice as a battery backup for generators. This battery has tolerance for both high and low temperatures.

DEKA uses gelled electrolyte technology as part of its commitment to quality and the environment. It is an ISO 9001, IATF 16949, and ISO 14001 certified manufacturer. This commitment to quality is in every product that it makes. This battery has a long life and makes an excellent deep-cycle choice for trolling. It has a low self-discharge rate, making it a good battery for boats that must go in seasonal storage or for solar power. Deka battery can withstand conditions that would destroy other batteries. Even if you leave it discharged for several months, it can still be charged and used again in some circumstances.

• Long, deep-cycle life

• Good storage characteristics

• Spill-proof design

• Dependable as a starting battery

• Resistant to vibration and shock

• Maintaining the preferred storage temperature at 77° isn’t always possible under home conditions.

9. Odyssey RedTop 31M-O B000TCRERQ PC21505T — Best Trolling Battery

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Odyssey makes batteries that have proven reliability and performance. This battery has standard SAE brass posts compatible with automotive clamps. They are corrosion-resistant and threaded for marine use, too. This battery has a highly stable voltage over long periods, making it a good choice for marine trolling motors and cars loaded with modern electronics. Another thing that makes this battery an excellent choice is that it accepts charge well and can be recharged quickly, even when fully discharged.

Odyssey stands behind its products and offers a generous, limited, full replacement warranty. Actual customer experiences reflect that these batteries can last up to two or three times the length of their warranty. This battery is resistant to hot and cold temperatures with an operating range of between -40° F to 176° F (-40° C to 80° C). When it comes to a marine battery, most are either for starting or deep cycle, with few choices that offer a balance of both. This one does, which is one of the main reasons why we recommend it. It has excellent performance in many categories and can hold up well under abuse.

• Wide operating temperature

• Reputation for long life

• Corrosion-resistant posts

• Suitable for starting and deep-cycle

• Accepts charge well, fast recharge

• Has SAE threaded terminals only

• Heavy to lift

10. NorthStar Elite ELT-AGM31 — Best Heavy-Duty Commercial Battery

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The NorthStar Elite made this list for several reasons. NorthStar is known as a reliable brand. It was made specifically for cars with Stop/Start technology in mind. Cars designed to stop the engine when the vehicle comes to a stoplight or heavy traffic place a high demand on the battery. The continual starts with only a short time to recharge the battery between them are one of the most challenging situations that a battery can face. This NorthStar battery is designed to work reliably in these circumstances without harming battery life.

This battery is a preferred brand for truckers, emergency vehicles, and fleet vehicles. It's maintenance-free, and it's the brand that people trust when starting is critical. NorthStar is made in the U.S. in an ISO 9001 and ISO 14001 certified facility. They meet the toughest standards for quality and manufacturing practices.

• Excellent cold starting ability

• Known for quality

• Dual-post terminal design

• Sturdy flip-up handle for carrying

• Space between the dual terminal posts is narrow and might not accommodate all connectors

Buyer’s Guide and FAQ

group 31 battery

CHOOSE
THE BEST IN 2024

Before purchasing your next battery, it is important to understand terms meaning and how they affect battery performance.

Now you have some of our picks for the best Group 31 batteries on the market. It’s a standard battery size available as either a deep-cycle battery, SLI battery, or combination battery and typically used for marine purposes, but it can also be used in some automobiles. Here are a few questions you might have about Group 31 batteries.

What Is the Best 31 Battery?

When it comes to an overall best 31 battery, it is difficult to determine the best one. Which one is best for you depends on your needs, the type of vehicle, weather, and how many electronics you need to operate. All of the batteries on this list are an excellent choice for their purposes.

When choosing a group 31 battery replacement, it is important to pay attention to specifications. Whether you have a boat, recreational vehicle, or passenger car, you need to make sure you not only get the proper physical size battery but that you get one that meets the minimum recommended amperage, cold-cranking amps, and other qualities. The best place to find this information is your Owner’s Manual.

What Is a Group 31 Battery and What Dimensions Should It Have?

A BCI Group 31 battery is used for marine purposes and in some cars and recreational vehicles. It has dimensions of 13 x 6.8 x 9.4 inches, or 330 x 173 x 240 mm (Length x Width x Height). Some come with threaded posts for a secure hold in high-vibration environments and boats. They have reserve capacities that range from 150-230 minutes.

People choose a Group 31 battery because they have high cold-cranking amps gives them the ability to start big boat engines. They also provide excellent car engine starting capability in cold weather. A Group 31 battery usually has between 600 and 1150 cold-cranking amps.

Several types of technologies are used in this type of battery. Some use thick plate technology, while others use think plate technology and other plate configurations. The technology used affects the cold-cranking amps, ampere-hours, and reserve capacity. Which one is right for you depends on the type of engine and your usage.

What is the Difference Between a Group 27, 8D, and a Group 31 Battery?

A Group 27 has dimensions close to those of a Group 31 battery. They are the same width, but they are a shorter length. They also have a shorter height. A Group 27 is around 90-100 ampere-hours, and they have a reserve capacity of around 190 minutes. A Group 27 will fit into the battery tray for a Group 31, but it isn’t a tight fit, and it can slide around lengthwise. This can cause problems with the connection and create a hazardous situation due to additional vibration and movement. If you put a Group 27 battery in your car or boat, make sure to change the tray to a proper size. In some cases, they are close enough to work in the same battery holder as long as they are secured properly.

A Group 8D battery is also of a similar dimension, but it is considered a commercial battery. This battery is used in fire trucks, emergency vehicles, and in larger boats where starting is critical. An average 8D battery weighs around 150 pounds, which is twice the weight of a Group 31 battery. If you decide to interchange the two, make sure your tray and mounting brackets are sturdy enough to take the weight, especially under normal road shocks. A Group 8D battery is considerably longer than a Group 31. A Group 8D battery’s dimensions are 20.75 x 11 x 10-inches, compared to a Group 31 battery that is 13 x 6.8 x 9.4 inches. It is more difficult to substitute an 8D for a 31 battery, and it will require a different battery holder.

How Long Do Group 31 Batteries Last?

Warranties on Group 31 batteries differ from 12 to 48 months. There is a wide range of variability in this battery group. One could expect the battery to last at least through its warranty and beyond. Proper battery care is an important part of making sure your battery has a long life. One way to do this is to ensure the vehicle battery is in a place that maintains temperature within the recommended range for that battery.

How long your battery will last also depends on whether you do things like leave your lights on or leave your phone on charge and drain the battery. A malfunctioning internal light that does not shut off can also do this. For some batteries, frequent stops and starts without much distance can drain the battery because the alternator does not have enough time to charge it up again. The effects of these types of actions on the battery’s longevity depend on the type of battery. Deep-cycle batteries can take this type of use better than SLI batteries.

Another thing can affect battery life is the type of charger you use. If you have a deep-cycle battery, you should use a charger designed for this purpose. You can also get a high-amperage fast charger to recharge your battery in only a few hours, but these can be detrimental. Some batteries are made to be used with fast chargers and can take it. For others, a trickle charger is best because a charger with too high amperage can create more current than the battery can accept. This can cause the battery to become hot and overheat. Draining the battery frequently and using the wrong charger can void the warranty. If you take care of your battery, you can expect it to last for many years.

How Many Amp-Hours is a Group 31 Battery?

A Group 31 battery is typically between 100-125 ampere-hours.

How Many Ampere-Hours does a Group 31 Deep Cycle Battery Hold?

There is no difference in the number of ampere-hours that a Group 31 deep-cycle battery will hold and a Group 31 SLI battery. The difference is how the battery discharges the energy. An SLI battery discharges a large portion of the power at once to start the engine. A deep-cycle battery discharges the same amount of power over a longer period.

How Do You Replace and Use a Group 31 Battery in a Car?

A Group 31 battery was designed for marine use, but some people choose to use it in their cars and trucks. This type of battery is an excellent choice for SUVs and trucks for off-road use and on rough roads because they are made to withstand heavy shock and vibration. They often have higher cold-cranking amps, which means they give more reliable starts in cold weather. Some people will also do this if they want to add bigger car lights, a more powerful stereo, or other accessories that require more electricity.

The first concern is making sure the battery will physically fit in the vehicle with enough clearance to close the hood and not interfere with anything surrounding it. If it has enough clearance, you will need to replace the battery tray with an appropriate size. You also might need to do a wiring upgrade, too, in some models. The bracket screws from the stock battery might also need to be upgraded. Finally, you might need to upgrade your alternator because a Group 31 requires more voltage to charge, but this depends on your vehicle and the size alternator already in it.

Here are the steps you will need to complete the installation if none of these other items need to be upgraded, except the battery holder and hold-downs.

• First, shut off your engine, put the emergency brake on, and raise the hood.
• Next, unscrew the connector on the terminal post on the negative battery terminal. Now, unhook the connector on the positive post.
• Lift the old battery out. Because of the Group 31 battery’s weight, make sure that the strap or carry handle has not deteriorated and become unreliable before using them.
• If you need to replace the battery holder and hold downs, do this now. Most screw off and on.
• Next, clean the battery terminal connectors and surrounding metal with a wire brush or sandpaper. Make sure that you remove all the corrosion might have built up over time. You want to have clean metal to clean metal.
• Lift the new battery into the new battery holder. Make sure it is properly seated and that it does not move around.
• Replace the battery hold down or install the new ones that purchased. Tighten them down so that the battery is secure.
• Reconnect the negative terminal and positive terminals. They are threaded and only need to be hand tight.
• You can now start the car and make sure everything works.

What is the weight of a Group 31 battery and a Group 31 Duracell deep cycle battery?

The weight of a Group 31 battery depends on its design. Some manufacturers use technology that allows them to put more lead plates into the battery. While this often provides better electrical conductivity, it also adds extra weight to the battery. The material that the case is made from also adds to the weight. Most of them tend to weigh between 70-75 pounds. A Duracell Ultra Platinum AGM Group 31 battery weighs 67 pounds.

How Long Does it Take to Charge a 35 Car Battery?

One of the biggest questions we get is how long it takes to charge a Group 31 battery. The answer to this question depends on the charger type and how far down the battery is drained. The charger’s amperage is the biggest determining factor in how long it will take to charge the battery.

You can purchase chargers that range from trickle chargers to high-amperage fast chargers. Although it might be tempting, you should never use a charger with a higher amperage than recommended for your battery. Doing so could damage your battery. This charge will give you an idea of how long it will take to charge your battery using different amperage chargers.

Final Word

Group 31 batteries are one of the most diverse battery groups as far as their differences in performance and specifications are concerned. They are one of the most common marine batteries, but they are also used in RVs, emergency vehicles, cars, and trucks. One of their advantages is cold-cranking amps and the ability to deliver reliable cold-starting capability. Many of the choices on this list have a good balance between cold-starting ability and deep-cycle capabilities.

Several battery brands on this list stand out for their quality and reliability. NorthStar, Odyssey, and Deka are a few of the brands noted for their quality of manufacturing, lifespan, and advanced technology. All of the batteries on this list are an excellent choice, depending on your purpose. Before choosing a battery, you must consider your weather conditions, type of vehicle, and whether you need a battery that favors starting ability or made for sustained electrical loads. Whether you need an SLI or Deep Cycle battery, this list is an excellent place to start.

Eric Strong

Eric Strong works in the automotive repair industry more than 12 years. His work included repairing electrical systems in various vehicle systems. A hybrid electric car battery replacement experience expanded his understanding of automotive battery technology.