Group 35 Battery

When people type “Group 35 battery” or “group 35 battery size” into Google, they are usually standing in front of a shelf of car batteries, trying to match a confusing label on their old battery. The number looks like a model name, but it isn’t obvious what it actually means, or whether a different size could work just as well.

In reality, Group 35 is a BCI (Battery Council International) case size code. It mainly defines the battery’s physical dimensions and terminal layout, so it fits properly in a vehicle’s battery tray. Within that shell, manufacturers can use different chemistries (flooded, AGM, even lithium), different Ah ratings and different CCA values.

This guide gives you a clear, practical overview of Group 35 car batteries:

• exact size and dimensions
• typical capacity, CCA and reserve capacity ranges
• common vehicle and application types
• how to choose a Group 35 battery that fits both your car and driving style
• when you should stop thinking in “Group 35” terms at all and move to a LiFePO4 traction pack, and how Saftec can help with those projects

Quick Answer: Group 35 Battery Size and Typical Specs

A Group 35 battery is a common 12 V automotive starter battery size used in many passenger cars, small SUVs and light trucks. Its case size is roughly:

• Approximate dimensions: about 9.0″–9.1″ long × 6.8″–6.9″ wide × 8.8″–9.0″ high
• Weight: typically 34–42 lb (about 15–19 kg), depending on chemistry and design
• Capacity range: about 45–65 Ah in typical lead-acid designs
• CCA range: roughly 550–750 A CCA for mainstream products
• Reserve capacity: about 90–120 minutes in many lines

Those numbers vary by brand, but they give you a realistic ballpark of what to expect when you see “Group 35” on the label.

Table 1 – Group 35 Battery Size and Key Ratings at a Glance

Parameter	Typical Group 35 Value*
Nominal voltage	12 V
Dimensions (L × W × H)	~9.1″ × 6.9″ × 8.9″ (230 × 175 × 225 mm)
Weight	~34–42 lb (15–19 kg)
Capacity range (lead-acid)	~45–65 Ah
CCA range	~550–750 A CCA
Reserve capacity	~90–120 min @ 25 A
Common applications	Passenger cars, crossovers, light trucks, some RV & marine cranking

*Exact specs depend on brand, chemistry and series. Always check the manufacturer’s datasheet.

What Is a Group 35 Battery and How BCI Group Sizes Work

BCI Group Size Definition for Automotive Batteries

BCI (Battery Council International) defines standard case sizes for automotive and marine batteries. A group number like 35 tells you:

• the approximate length, width and height of the battery case
• the terminal type and position (for example, top posts with positive on the right)
• the general shape that vehicle manufacturers design their trays and hold-downs around

The group size does not directly specify:

• voltage (most automotive groups are 12 V)
• amp-hour capacity
• exact CCA or reserve capacity
• internal chemistry (flooded, AGM, EFB, lithium, etc.)

So when you read “Group 35 battery”, you should think “a battery that physically fits the Group 35 footprint” rather than “a battery with 35 Ah” or “35 volts.”

Where Group 35 Fits Among Common Car Battery Groups

Group 35 sits in the medium-size segment of the BCI lineup. Nearby you’ll find:

• Group 24 / 24F – slightly longer cases, used in many mid-size sedans and SUVs
• Group 51R – narrower, more compact batteries common in small cars
• Group 27 – longer, larger cases often used in RV, marine and heavy-duty applications

This is why you often see questions like “difference between group 24 and 35 battery” or “can I use a 24F instead of 35?” — people are trying to understand how these sizes relate. We cover that comparison in detail in a separate 24F vs 35 guide and only summarize it briefly later in this article.

To find your own group size:

• check the label on your old battery,
• look in the owner’s manual, or
• use an online fitment guide for your vehicle’s make, model and year.

Group 35 Battery Dimensions, Weight and Terminal Layout

Standard Group 35 Case Dimensions

BCI defines Group 35 with approximate dimensions of:

• Length: about 9.06″–9.10″ (230 mm)
• Width: about 6.77″–6.88″ (172–175 mm)
• Height: about 8.74″–8.88″ (222–225 mm)

Manufacturers typically stay within a few millimetres of these values, but decorative handles, caps and labels can add a little extra height or width. That is why it is smart to:

• measure your existing battery, and
• visually check clearance to the hood, strut brace, and neighbouring components.

Typical Weight and Why It Matters

Most lead-acid Group 35 car batteries weigh between 34 and 42 lb (15–19 kg). Variations come from:

• thicker plates and higher capacity designs (heavier)
• AGM constructions with more lead and glass mat (often heavier)
• lighter cases or lithium-based designs (lighter)

Weight matters because:

• the battery tray must support it securely
• extra weight at the front of the vehicle can slightly affect handling
• a much heavier or lighter battery than stock might require different hold-down hardware

For normal passenger cars the difference is small, but off-road builds and performance vehicles sometimes care about every kilogram.

Top Post Locations and Polarity for Group 35 Car Batteries

Group 35 batteries usually use top posts with a standard layout:

• When facing the front label, the positive terminal is typically on the right.
• Some manufacturers add side terminals or threaded studs for accessories.

Before buying a replacement Group 35:

1. Check which side the positive terminal sits on in your current battery.
2. Confirm that the cable lengths and routing will reach the new terminals without stretching or crossing.
3. Make sure protective covers, fuses and brackets clear the posts properly once installed.

Matching terminal layout is just as important as matching group size.

Group 35 Battery Capacity, CCA Ratings and Reserve Capacity

Voltage, Amp-Hour Capacity and Usage Pattern

Like most automotive starter batteries, Group 35 products are:

• Nominal voltage: 12 V
• Typical capacity: roughly 45–65 Ah in flooded lead-acid, with some AGM designs reaching higher values
• Designed for: short, high-current bursts to crank the engine, followed by immediate recharge

They are not deep-cycle batteries. Repeatedly discharging them to low state of charge (for example, below 50%) will greatly shorten their life.

CCA and Starting Performance for Group 35 Batteries

CCA (Cold Cranking Amps) is a key rating for starter batteries. Many Group 35 models offer:

• around 550–750 A CCA for mainstream ranges,
• premium AGM models can go higher.

What you actually need depends on:

• engine displacement and compression
• type of fuel (diesel engines usually need more CCA)
• climate (cold winters demand more margin)

As a rule of thumb:

• For small petrol engines in mild climates, 550–600 CCA is often plenty.
• For larger engines or colder regions, looking for 650–750 CCA makes sense.

Going above the manufacturer’s recommended CCA does not damage your car; it simply gives you more reserve ability for hard starts.

Reserve Capacity and Accessory Runtime

Reserve capacity (RC) measures how long a fully charged battery can supply a modest load (usually 25 A) before dropping to a specified voltage. Group 35 batteries typically offer:

• RC around 90–120 minutes, depending on design.

RC matters if you:

• listen to audio with the engine off,
• run lights, inverters or CPAP machines during short stops,
• frequently use accessories in “key on, engine off” situations.

Still, if you need many hours of runtime every night, you should be thinking in terms of a dedicated deep-cycle or LiFePO4 pack, not simply a larger Group 35 starter battery.

Table 2 – Typical Spec Ranges for Group 35 Lead-Acid Batteries

Spec	Typical Group 35 Range*
Capacity (Ah)	45–65 Ah
CCA	550–750 A
Reserve capacity (RC)	90–120 min
Weight	34–42 lb (15–19 kg)
Recommended usage pattern	Engine starting, shallow discharges

*Always check the datasheet of the specific model you are buying.

Common Group 35 Battery Applications and Compatible Vehicles

Passenger Cars and Crossovers That Commonly Use Group 35

Automakers often choose Group 35 for:

• compact and mid-size sedans
• small to medium crossovers and SUVs
• some light trucks and minivans with moderate electrical loads

It is especially common on Japanese and Korean vehicles where engine bays are designed around compact rectangular trays.

Instead of memorising a brand/model list, simply:

• look up your vehicle in an online fitment catalog, or
• ask a reputable retailer to cross-check your make / model / year / engine.

Light Trucks, RV and Marine Uses for Group 35 Size

Group 35 batteries are sometimes used as:

• starting batteries on small outboard engines and boats,
• crank batteries for compact RVs and camper vans,
• generator start batteries for small gensets.

In these cases, Group 35 works well as long as:

• the engine’s starting requirements match the battery’s CCA, and
• you are not deeply cycling the battery for house loads day after day.

For heavy house loads in RVs and boats, a separate deep-cycle bank is recommended.

How to Confirm Your Vehicle Needs a Group 35 Battery

To avoid guesswork:

1. Check the owner’s manual for the specified BCI group size.
2. Read the label on the original battery (often printed as “BCI Group 35”).
3. Use a fitment lookup tool from a trusted battery supplier.
4. If your car has been modified, measure the tray and hold-downs and compare against Group 35 dimensions.

Never rely solely on “it looks about the same size” when swapping batteries.

How to Choose the Right Group 35 Car Battery for Your Vehicle

Matching Group 35 Battery Specs to Climate and Driving Style

When selecting a replacement Group 35 car battery, consider:

• Climate
  • Cold climate → prioritise higher CCA and quality construction.
  • Very hot climate → look for batteries rated for high-temperature durability.
• Driving pattern
  • Short, frequent trips create more engine starts and less time to recharge.
  • Long highway drives are easier on the battery.
• Electrical load
  • Extra lights, audio amplifiers, inverters, winches or aftermarket electronics increase demand.

If you push your electrical system hard, aim for the upper half of the CCA and RC range and choose a robust design (often AGM or enhanced flooded).

Flooded vs AGM vs EFB Group 35 Options

You will often see three main technologies in Group 35:

1. Flooded lead-acid (wet cell)
   • Lowest upfront cost
   • Adequate for normal use
   • Requires ventilation and is more sensitive to deep discharge
2. AGM (Absorbent Glass Mat)
   • Higher CCA and RC in similar case size
   • Better vibration resistance and spill-proof
   • Handles partial state of charge better and often lasts longer
   • Higher price than flooded
3. EFB (Enhanced Flooded Battery)
   • Strengthened flooded design for vehicles with stop-start systems
   • Improved cycle life compared with conventional flooded

For a typical non–stop-start vehicle, the choice is often between good flooded for budget or AGM for performance and robustness.

Warranty, Brand and Total Cost of Ownership

Price is important, but you should also look at:

• Warranty length and conditions
• The brand’s reputation for quality control
• Independent test results or user reviews where available

A cheap battery that fails early can end up costing more than a stronger battery with a longer service life and better warranty support.

Group 35 Battery Equivalents and Comparison with Other Sizes

Group 35 vs Group 24 and 24F in Everyday Use

Group 24 and 24F batteries are:

• longer and often slightly heavier than Group 35
• capable of slightly higher Ah and RC in many product lines
• used where trays provide more length

Group 35, in contrast, is a more compact footprint, suited to tighter engine bays. Some vehicles can accept both with tray adapters; others must strictly use one size.

If you want an in-depth, spec-by-spec breakdown of 24F vs 35, including when it is safe to swap, see our dedicated guide on 24F vs 35 battery, where we cover dimensions, CCA and fitment in detail.

Group 35 vs 51R and Other Compact Battery Groups

Other small and mid-size battery groups you may encounter include:

• Group 51R – narrower and sometimes taller; common in small cars
• Group 26R and 34 – used in various compact SUVs and light trucks

While these cases may look similar on the shelf, their:

• length and width,
• base rail shapes, and
• terminal positions

are often different enough that they cannot be safely interchanged without modifying trays and cables.

When You Can and Cannot Swap to a Different Group Size

Swapping away from Group 35 should only be considered if:

• the tray dimensions and hold-down can secure the new group size,
• cable lengths and polarity still match correctly, and
• the new battery meets or exceeds the required CCA and RC.

If any of those conditions are not clearly satisfied, stick with the OEM-specified Group 35.

Group 35 Lithium and LiFePO4 Options: Pros and Limitations

Drop-In Lithium Replacements in Group 35 Case

Some manufacturers offer lithium-based “drop-in” Group 35 batteries. They are built in a Group 35 shell and contain:

• a LiFePO4 or other lithium chemistry pack, and
• an internal BMS (Battery Management System).

Benefits often include:

• much lower weight
• higher usable capacity at shallow to medium currents
• very low self-discharge

However, there are important limitations.

Safety, BMS and Charging Considerations

Before using a lithium drop-in as a Group 35 car starter battery, you must ensure:

• the BMS is designed for high cranking currents and short bursts
• its voltage range is compatible with your alternator and smart charging system
• it has temperature protection, especially for low-temperature charging
• the manufacturer explicitly approves use as an engine starting battery

Using a generic LiFePO4 battery (without the right BMS and approvals) purely as a drop-in Group 35 replacement can create safety and reliability risks.

Why Traction LiFePO4 Packs Are Different from Group 35 Starters

A Group 35 lithium starter battery still behaves like a starter battery: it is designed around short, high-current bursts and shallow discharges.

By contrast, a LiFePO4 traction pack is designed for:

• continuous discharge at moderate currents,
• thousands of deep cycles, and
• integration with motor controllers and advanced chargers.

For applications such as electric scooters, e-rickshaws, low-speed EVs, delivery trikes or custom energy storage systems, a traction pack is the correct solution—not a Group 35 starter battery.

When to Move Beyond Group 35 to a LiFePO4 Traction Pack

Use Cases Where Group 35 Starter Batteries Are Not Enough

You should start thinking beyond Group 35 if:

• you are powering electric drive motors instead of a combustion engine,
• your loads draw significant current for hours every day, or
• you regularly discharge the battery well below 50% state of charge.

Examples include:

• electric two-wheelers and three-wheelers
• low-speed four-wheel EVs and utility carts
• last-mile delivery vehicles
• off-grid DC equipment and mobile machinery

In those scenarios, starter batteries (even AGM ones) will suffer premature failure if used as the main energy source.

Designing Around System Voltage and kWh, Not Group Size

For traction and storage applications, the key design parameters shift to:

• System voltage: 24 V / 48 V / 60 V / 72 V or custom values
• Total energy: kWh capacity based on daily usage
• Peak and continuous current requirements
• Mechanical integration: pack shape, mounting and IP rating

In other words, instead of asking “which Group size,” you should ask “what voltage and kWh do I need, and what is the best pack layout for my vehicle or system?”

Benefits of LiFePO4 Traction Batteries for E-Mobility and Storage

Properly designed LiFePO4 traction batteries offer:

• High cycle life – often 3,000–6,000 cycles at typical depths of discharge
• Deep discharge capability without dramatic life penalties
• Stable voltage and good power delivery over a wide state-of-charge range
• Improved safety compared with many other lithium chemistries
• Weight reduction versus equivalent lead-acid banks

This is where Saftec focuses its R&D and production capacity.

About Saftec LiFePO4 Energy Storage and EV Power Battery Manufacturer

Saftec Product Lines for Storage and EV Power

Saftec is a LiFePO4 energy storage and EV power battery manufacturer. Instead of selling universal Group 35 starter batteries, we specialise in:

• Home and small commercial energy storage systems
• Rack-mount and cabinet LiFePO4 batteries for telecom, data and backup power
• Traction batteries for electric two-wheelers, three-wheelers and low-speed four-wheel vehicles

Our products are built around system voltage, energy and cycle life, not fixed BCI group sizes.

OEM and ODM Services for Vehicle and Energy Projects

For OEM customers and engineering partners, Saftec offers:

• Custom pack design based on your space, voltage and range requirements
• Cell selection and module layout optimised for performance and cost
• Integrated BMS with CAN / RS485 communication for motor controllers and EMS
• Housings with appropriate IP rating, mounting points and thermal management

We can work from your drawings or collaborate from concept stage to deliver a safe, production-ready LiFePO4 pack.

Distributor and Dealer Programs for Regional Partners

Saftec also supports:

• regional distributors and dealers of LiFePO4 storage and traction batteries
• EV manufacturers, retrofit shops and system integrators looking for a stable, long-term battery partner

Partners receive technical documentation, training resources and responsive after-sales support to help them grow their local markets.

If you are planning e-mobility or energy storage projects and need reliable LiFePO4 packs rather than another Group 35 starter battery, Saftec is ready to discuss a tailored solution.

FAQs: Group 35 Battery Size, Use and LiFePO4 Alternatives

Q1. Is a Group 35 battery the same size as a 24 or 24F battery?
No. Group 35 is shorter than most Group 24 and 24F cases, although the width and height are similar. A 24 or 24F usually offers a little more capacity and RC but needs a longer tray. Always verify tray length and hold-down design before switching groups.

Q2. What is a Group 35 battery equivalent if I can’t find that size in my area?
Some regions list batteries by local codes rather than BCI numbers. The safest approach is to use the dimensions and terminal layout of Group 35 and ask a supplier to cross-reference a case that matches those numbers and meets your CCA requirement.

Q3. How long does a typical Group 35 battery last in normal car use?
In a healthy charging system and moderate climate, a quality Group 35 starter battery often lasts 3–5 years. Frequent deep discharges, extreme heat or many short trips can shorten life significantly, while careful maintenance and conservative use can extend it.

Q4. Can I use a Group 35 battery as backup power for a CPAP machine?
For occasional emergency use, a fully charged Group 35 can run a CPAP machine via an inverter or DC adapter for a limited number of hours. However, regularly cycling a starter battery to low state of charge for CPAP is not ideal. A dedicated deep-cycle or LiFePO4 pack is a better long-term solution.

Q5. Are AGM Group 35 batteries always better than flooded ones?
AGM Group 35 batteries usually provide more CCA, better vibration resistance and improved performance under partial state of charge, but they cost more. For light duty in mild climates, a good flooded battery may be perfectly adequate. AGM makes more sense when you need extra robustness or run many accessories.

Q6. Do I need to upgrade alternator or wiring when switching to a Group 35 lithium battery?
If you are using a true drop-in lithium starter battery that is approved for automotive use and compatible with your charging voltage, you generally do not need to change the alternator or wiring. However, you must follow the manufacturer’s installation instructions and avoid using generic LiFePO4 packs without proper BMS protection as automotive starters.

Q7. When should I stop thinking about Group 35 and design a LiFePO4 traction pack instead?
Once your project involves driving an electric motor or supporting heavy daily loads for hours (for example, delivery trikes, e-rickshaws or off-grid equipment), the limitation is no longer which Group size fits the tray. At that point, you should design around system voltage and kWh and use a LiFePO4 traction pack engineered for deep cycling—exactly the kind of solution Saftec provides.