Compare group size, cold cranking amps and warranty
Spiral-cell AGM built for vibration resistance
SpiralCell AGM constructionStrong vibration resistanceColour-coded ranges for starting and deep cycleSealed and spill-proofPremium pricing
High cranking power and deep-cycle capability
Pure lead AGM constructionHigh cold cranking amps for the sizeDeep cycling capabilityLong service life claimsSuited to heavy accessory loads
Long-standing brand with wide fitment coverage
Broad group size coverageAGM and flooded optionsWidely available through retail partnersEstablished warranty networkStart-stop compatible ranges
OE-standard batteries across many vehicles
Original equipment supplier for many vehiclesProfessional and Gold rangesMaintenance-free designsWide fitment coverageBacked by a large dealer network
Nationwide fitting and warranty support
Extensive nationwide store networkIn-store testing and fittingAGM and conventional optionsWarranty serviceable at any branchCompetitive pricing| Product | Optima 9.6 | Odyssey 9.1 | DieHard 8.5 | ACDelco 8.0 | NAPA 7.4 |
|---|---|---|---|---|---|
| Highlights | SpiralCell AGM construction · Strong vibration resistance · Colour-coded ranges for starting and deep cycle · Sealed and spill-proof · Premium pricing | Pure lead AGM construction · High cold cranking amps for the size · Deep cycling capability · Long service life claims · Suited to heavy accessory loads | Broad group size coverage · AGM and flooded options · Widely available through retail partners · Established warranty network · Start-stop compatible ranges | Original equipment supplier for many vehicles · Professional and Gold ranges · Maintenance-free designs · Wide fitment coverage · Backed by a large dealer network | Extensive nationwide store network · In-store testing and fitting · AGM and conventional options · Warranty serviceable at any branch · Competitive pricing |
Editorially scored by our research team.
Every score out of 10 is assigned by our editors from published pricing, features, fees, coverage and support terms — not from user-submitted reviews. Scores are our own opinion and change as products change. Read our full methodology.
Optima is our top-scoring pick in Car Batteries, at 9.6/10 — it highlights “SpiralCell AGM construction”.
Odyssey scores 9.1 and is the one to compare against it — it highlights “Pure lead AGM construction”.
Both scores are our editors’ assessment of published specifications, pricing and terms against the criteria in our rating methodology — they are not aggregated customer reviews.
A car battery has to physically fit, seat securely and present its terminals the right way round. That is governed by the group size — a standardised code covering dimensions, terminal type and terminal position.
Find yours in the owner's manual, printed on the existing battery, or through a retailer's vehicle lookup. Getting this wrong means a battery that will not clamp down, or cables that will not reach — and a battery that moves in its tray fails early from vibration.
CCA measures the current a battery can deliver at low temperature while holding usable voltage. Cold thickens engine oil and slows the chemistry, which is why batteries fail on winter mornings.
Meet or exceed the manufacturer's specification. Exceeding it substantially does not damage anything and does not help much either — the starter draws what it needs. In a cold climate, headroom is worth having; in a mild one, matching the spec is fine.
Also note reserve capacity, which indicates how long the battery can run the car's electrics if charging fails. It matters more than CCA if you make short trips with a heavy accessory load.
Flooded lead-acid is the traditional, cheapest type. Fine for older vehicles with modest electrical demands.
AGM holds its electrolyte in glass mat separators. It is sealed, spill-proof, far more vibration-resistant, handles deep discharge better and recharges faster. It costs considerably more and is required by many vehicles with start-stop systems and heavy electronics.
EFB sits between them and is common as original equipment on entry-level start-stop cars.
The rule that matters: do not downgrade. If your car came with AGM, fit AGM. A flooded battery in a start-stop vehicle will fail prematurely because it is not designed for the repeated cycling.
Many cars from roughly the last decade run a battery management system that tracks the battery's age and condition and adjusts charging accordingly. On those vehicles a new battery must be registered to the car with a diagnostic tool, and sometimes the type must be specified.
Skipping this means the system keeps charging as though the battery were old, which shortens the new battery's life. Check whether your vehicle requires it before fitting one yourself.
Warranties are usually quoted as a free-replacement period followed by a prorated period. The free-replacement months are the part that matters; prorated cover typically gives a discount against list price rather than a replacement.
Check also where the warranty is serviceable. A battery bought online with a mail-in claim is a very different proposition from one replaceable at any branch of a national chain — batteries are heavy and fail inconveniently.
Check the manufacture date on the battery too, usually a stamped code. Batteries self-discharge on the shelf, and one sitting for a year has already used part of its life.
Most failures are not age alone. Repeated short journeys never fully recharge the battery; heat degrades it faster than cold, so a summer of high temperatures often causes a failure that appears on the first cold morning; a parasitic drain from an accessory flattens it overnight; and corroded terminals cause starting problems that look like a dead battery.
Before buying, have the charging system tested. A failing alternator destroys new batteries as efficiently as old ones, and replacing the battery alone means doing it again shortly.
Group sizes, CCA requirements, registration procedures and warranty terms vary by vehicle and manufacturer. Check your owner's manual, and have the charging system tested before replacing a battery.