720 Cold Cranking Amps
The Group 35 REDTOP delivers:
720 CCA
Cold Cranking Amps measure how much current a battery can deliver under standardized cold-weather conditions while maintaining sufficient voltage.
That makes CCA especially important when:
- Temperatures drop
- Engine oil thickens
- Starter load rises
- Engine compression is high
The 720CCA rating gives the Group 35 REDTOP substantial starting performance for compatible applications.
Designed Primarily for Starting
This is an important distinction.
The OPTIMA Group 35 REDTOP is a:
starting battery
It is not intended to be repeatedly deeply discharged.
Its ideal operating cycle is:
- Start the engine.
- Let the alternator take over.
- Recharge the battery quickly.
That makes it a good fit for vehicles with:
- Stock electrical systems
- Mild electrical upgrades
- Normal accessory loads
- Strong charging systems
If you regularly operate high-current accessories with the engine off, a YELLOWTOP is generally a better match.
REDTOP vs. D35 YELLOWTOP
Both batteries fit many Group 35 applications, but their intended uses differ.
OPTIMA 35 REDTOP
Best for:
- Strong engine cranking
- Mostly stock electrical systems
- Basic accessory loads
- Vehicles that recharge immediately after starting
OPTIMA D35 YELLOWTOP
Better for:
- Large audio systems
- Dash cameras
- Alarms
- Auxiliary lighting
- Air suspension
- Engine-off accessory use
- Repeated cycling
The REDTOP offers stronger pure starting emphasis, while the D35 YELLOWTOP is designed for both starting and cyclic use.
44Ah Capacity
The Group 35 REDTOP provides:
44 amp-hours
That gives the battery enough stored energy for normal automotive operation while keeping the design focused on high-current starting.
Amp-hour capacity matters because modern vehicles continue powering electronics even when the engine is off.
Possible loads include:
- Alarm systems
- Keyless-entry modules
- ECU memory
- Telematics
- Infotainment memory
If those loads become excessive, however, even a premium battery can discharge over time.
90-Minute Reserve Capacity
The Group 35 REDTOP is rated at:
90 minutes of reserve capacity
Reserve capacity measures how long a fully charged battery can support a standardized 25-amp load before reaching its specified discharge threshold.
That provides useful electrical reserve if the charging system fails.
However, reserve capacity does not make the battery a deep-cycle design.
SPIRALCELL TECHNOLOGY
The Group 35 REDTOP uses OPTIMA’s traditional:
SPIRALCELL TECHNOLOGY
Instead of conventional flat plates, OPTIMA uses tightly wound spiral cells.
The company describes the construction as using:
99.99% pure lead
Advantages of the design include:
- Strong current delivery
- Low internal resistance
- Good recharge capability
- High vibration resistance
- Consistent starting performance
The cylindrical cell design is one of the features that distinguishes traditional OPTIMA batteries from conventional flat-plate AGM batteries.
AGM Construction
AGM stands for:
Absorbent Glass Mat
The electrolyte is absorbed into fiberglass separators rather than freely moving inside the battery case.
Benefits include:
- Maintenance-free operation
- Spill-resistant construction
- Improved vibration resistance
- Strong starting output
- Good charge acceptance
- Flexible mounting capability
That makes AGM construction useful for performance, off-road and modified vehicles.
Up to 15 Times More Vibration Resistant
OPTIMA advertises its REDTOP construction as offering significantly greater vibration resistance than conventional flooded batteries.
That matters in vehicles exposed to:
- Rough pavement
- Off-road terrain
- Stiff suspension
- Engine vibration
- Chassis movement
Repeated vibration can damage internal battery components over time.
The REDTOP is designed to tolerate more punishment.
It still needs to be securely clamped into the vehicle.
Up to Three Times Longer Life
OPTIMA advertises up to:
3x longer life versus conventional flooded batteries
under suitable conditions.
Actual lifespan depends on:
- Charging voltage
- Temperature
- Parasitic draw
- Driving frequency
- Storage
- State of charge
- Alternator condition
Repeatedly leaving any starting battery discharged will shorten its life.
Faster Recharge Capability
The REDTOP is designed to accept charge efficiently after starting.
That is useful because the battery may discharge several hundred amps for a few seconds while operating the starter.
Once the engine starts, the alternator replenishes the energy.
Recharge performance still depends on:
- Alternator output
- Charging voltage
- Battery temperature
- Electrical load
A battery cannot recharge properly if the charging system is weak.
Fully Charged REDTOP Voltage
A fully charged OPTIMA REDTOP typically measures approximately:
12.6 to 12.8 volts
after resting.
A battery measuring substantially below that may require charging or testing.
Resting voltage alone does not prove the battery is healthy, however.
A weak battery can still show acceptable voltage until a heavy load is applied.
Great for Hot Rods
The Group 35 REDTOP is a strong choice for compatible hot rods because it combines:
- Compact dimensions
- High CCA
- AGM construction
- Vibration resistance
- Maintenance-free operation
Hot rods often benefit from strong cranking output, especially with:
- High-compression engines
- Modified ignition systems
- High-torque starters
- Limited battery space
Always verify the actual battery tray and terminal arrangement.
Good for Off-Road Vehicles
Off-road applications expose batteries to:
- Vibration
- Impact
- Heat
- Dust
- Steep angles
The sealed AGM design makes the REDTOP better suited to these conditions than many conventional flooded batteries.
However, if the vehicle operates a winch extensively with the engine off, consider a YELLOWTOP instead.
Winching can deeply discharge a battery.
Ideal for Basic Electrical Demands
OPTIMA positions the Group 35 REDTOP for vehicles with relatively normal electrical loads.
Examples include:
- Factory stereo
- Normal lighting
- Factory electronics
- Mild accessories
If your build has become a rolling electronics convention, step up to a dual-purpose battery.
Car Audio Systems
A small or moderate audio system can operate perfectly well with a REDTOP when the alternator supplies enough current.
But large amplifiers can place much greater demand on the electrical system.
Our Car Audio System Guide explains how battery capacity, alternator output, grounding and cable size work together.
If the audio system is used heavily with the engine off, the D35 YELLOWTOP is generally the better battery choice.
Battery Light On?
If the battery warning lamp stays illuminated while the engine is running, do not automatically replace the battery.
The warning usually points toward the charging system.
Possible causes include:
- Alternator failure
- Voltage regulator failure
- Broken belt
- Damaged charging cable
- Poor ground
- Main fuse failure
- Fusible-link failure
Our Why Is My Battery Light On? guide explains what to test before replacing the battery.
Check the Fusible Link
Some vehicles use a fusible link between the alternator, starter and battery.
If it opens, charging current may not reach the battery.
Our What Is a Fusible Link? Fusible Link vs. Fuse Explained guide explains how these high-current protection circuits work.
Never bypass a fusible link with ordinary wire.
That removes important circuit protection.
Rapid Clicking When Starting
Rapid clicking usually means system voltage is collapsing during a start attempt.
Possible causes include:
- Weak battery
- Discharged battery
- Loose terminal
- Corroded cable
- Poor ground
- Starter issue
- Charging problem
Our Rapid Clicking When Starting a Car guide explains how to isolate the problem.
Test first.
Replace second.
Car Has Power but Won’t Start
A car can still operate:
- Dash lights
- Radio
- Interior lights
- Power locks
while the battery is too weak to crank the engine.
The starter motor requires dramatically more current than most accessories.
If the car has electrical power but won’t crank, use our Car Has Power but Won’t Start guide.
Check Battery Cables
High starting current makes battery cable resistance extremely important.
Inspect:
- Positive cable
- Negative cable
- Engine ground strap
- Chassis grounds
- Starter terminal
Corrosion inside a cable can create enough voltage drop to prevent cranking even when the battery itself is healthy.
Battery Registration on Modern Cars
Some newer vehicles require battery registration after replacement.
The charging system may track:
- Battery age
- Capacity
- State of charge
- Charging history
Our What Is Battery Registration, and Does Your Car Need It? guide explains when a replacement battery needs to be registered or coded.
Always follow the vehicle manufacturer’s replacement procedure.
Maintenance-Free Design
The Group 35 REDTOP is maintenance-free under normal conditions.
There is no routine need to:
- Add water
- Check electrolyte
- Remove battery caps
You should still inspect:
- Terminals
- Cable connections
- Battery hold-down
- Case condition
- Charging voltage
Maintenance-free does not mean immune to electrical problems.
Flexible Mounting
The AGM construction allows more mounting flexibility than a conventional flooded battery.
That can be useful for:
- Hot rods
- Custom builds
- Off-road vehicles
- Performance cars
Always maintain proper terminal clearance and follow OPTIMA mounting requirements.
The positive terminal must never contact the hood or chassis.
Who Should Buy the OPTIMA 35 REDTOP?
The Group 35 REDTOP makes the most sense for drivers who want:
- Strong starting performance
- 720CCA
- AGM durability
- Maintenance-free operation
- High vibration resistance
- Compact Group 35 dimensions
- Normal accessory support
It is especially attractive for compatible:
- Performance cars
- Hot rods
- Trucks
- Off-road vehicles
- Daily drivers
Why Buy the OPTIMA Group 35 REDTOP?
Key features include:
- 720 Cold Cranking Amps
- 44Ah capacity
- 90-minute reserve capacity
- SPIRALCELL TECHNOLOGY
- 99.99% pure lead construction
- AGM design
- Strong vibration resistance
- Fast recharge capability
- Maintenance-free operation
- SAE top terminals
- Strong cold-weather starting performance
For vehicles that need a premium high-output starting battery without regular deep-cycle use, the OPTIMA 35 REDTOP AGM Battery is a strong choice.
Specifications at a Glance
Brand: OPTIMA Batteries
Series: REDTOP
Model: 35
Group Size: 35
Battery Type: AGM Starting Battery
Voltage: 12V
Cold Cranking Amps: 720 CCA
C20 Capacity: 44Ah
Reserve Capacity: 90 minutes
Length: 9.38 inches
Width: 6.75 inches
Height: 7.69 inches
Weight: 31.7 lb
Terminal Type: SAE top posts
Technology: SPIRALCELL
Primary Use: Engine starting
Maintenance: Maintenance-free
Before ordering, verify the vehicle’s required battery size, terminal position, CCA specification and electrical demands.
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