Choose a battery by what your car needs, in this order: the same BCI group size, the same type (flooded, enhanced flooded, AGM), then cold cranking amps that meet or exceed the car maker's specification. Only then compare reserve capacity, the date code on the case and the warranty. A start-stop car may need an EFB or an AGM; the pages we read say not to step down. Free-replacement periods printed for the consumer lines tabled below run from 18 to 48 months (commercial terms are shorter), and a longer warranty is a contract term, not a measure of life. We tested nothing, so there is no ranking here: the lists below are the specs and terms the makers printed on 5 November 2026, with what we could not read. Take the group, type and CCA from your manual, or from the old label if it prints them; the counter checklist is at the end. Consumer Reports' ratings are behind a member wall and belong to models, not brands.
We make PulsCar, an app that works with a car's diagnostic port. We sell no batteries, and there are no affiliate links on this page. We did not test, buy or install any battery for it. What it does is read what other people print: the trade body Battery Council International (BCI), battery makers including Interstate, East Penn (Deka), Clarios, Optima, DieHard, Duralast and Bosch, the owner's manuals of GM, Hyundai, Subaru and Nissan, Consumer Reports, AAA, and US government pages, all read on 5 November 2026 and saved as text. Pages that blocked us are listed at the end, not bypassed.
The question this page answers is narrow on purpose. Your battery is dead or dying and you must choose a replacement. Which group size, which type, how many cold cranking amps, what do reserve capacity, the date code and the warranty mean, and which lines suit which situation? It does not price the job (our car battery replacement cost guide does), it does not test your old battery (see how to test a car battery) and it does not diagnose a battery that keeps dying (see why a car battery keeps dying).
What to match, in what order
The mistake that costs the most is to start from the brand. The pages we read start from the car. Seven things matter, and the first three are not a choice: the car decides them.
Two sentences set the tone. Interstate's page on cold cranking amps says: "Your car's manufacturer typically recommends a specific CCA rating based on the engine size and design." And BCI describes its own role as supplying data that, in its words, provides "a recommended replacement battery BCI Group Size based on the battery that originally shipped with the vehicle."
Step one: the BCI group size, and what it fixes
A group size is a trade standard that says which batteries are interchangeable on size and terminals. BCI's group size page states the idea this way: "Batteries are classified into numbered group sizes according to their voltage, maximum overall dimensions, terminal arrangement, and special features that may affect battery fit." It lists four characteristics that identify a group: the physical size, the performance (cold cranking amps or amp hours, depending on the age of the vehicle), the position of the terminals, and the chemistry. For size it adds that batteries "within a certain group size must be the same physical size (i.e., within 2mm)".
That means a group number tells you two things at once: the battery will fit the tray and the cables will reach the posts. By default, BCI says, "the battery is assumed to use lead chemistry with flooded technology", and designations are assigned for the higher-performance variants, EFB and AGM. So a group number alone does not tell you the type; the car's requirement does.
Where to find yours. There are three places. The label on the battery now in the car; the owner's manual; and a retailer's or maker's fit guide. GM's 2026 Silverado manual says: "Refer to the replacement number shown on the original battery label when a new battery is needed." A Hyundai IONIQ 5 manual (2023) prints a battery label as an example: 60 Ah, 92 minutes of reserve capacity and 550 CCA. BCI publishes the vehicle-by-vehicle data book behind the fit guides, and says it covers more than 160,000 vehicles. We could not read the book itself, only BCI's description of it.
The terminals are part of the size. BCI's reference chart lists, next to the dimensions, the positive terminal location, a DIN code and a European (EN) code. The chart shows pairs that are the same case with opposite polarity: group 99 and group 99R both measure 207 by 175 by 175 millimeters, and the chart lists the positive terminal on the left for 99 and on the right for 99R. The same chart ties the common groups 47, 48 and 49 to the European DIN sizes H5, H6 and H8, which is why many catalogs print them as 47/H5, 48/H6 and 49/H8. If a battery is the right size but the posts are on the wrong side, the cables may not reach.
One group, a wide range of ratings. BCI's group table prints "O.E. Performance Ranges (for Reference Only)" for each group, the performance of the original-equipment batteries that group serves. For group 35 the range printed is 300 to 640 CCA, for 24F it is 250 to 900, for 65 it is 540 to 880 and for 51R it is 295 to 500. A single group serves cars with very different engines, which is the reason the CCA you need comes from your car, not from the group number.
What a group size does not settle. It does not settle the type: the same group can be sold as flooded, EFB or AGM, and Interstate's M and MTX lines both list group 65 without being the same battery. Nor does it settle the warranty or the age of the stock.
Step two: flooded, EFB or AGM, and why the car decides
BCI's glossary gives the three terms. An EFB is "a vented (flooded) lead-acid starter battery with additional design features to significantly improve the cycling capability and service life compared to standard flooded batteries, especially for start-stop vehicle applications." An AGM is built with a separator of glass microfibers that absorbs the electrolyte, "leaving no free electrolyte in the cell to spill". BCI's chemistry paper explains why: vehicles with start-stop functionality "required that lead-acid batteries have improved charge acceptance and function at lower states of charge", and the answer was enhanced flooded and modified AGM designs.
So there are three tiers of the same lead-acid battery, and cars are designed around one of them. The question is not which is best but which the car expects.
What the car makers' manuals say. We could read four US owner's manuals and a Hyundai owner page. The clearest is GM's. The 2026 Silverado 1500 manual states: "Vehicles with the Stop/Start system have an Absorbed Glass Mat (AGM) 12-volt battery. Installation of a standard 12-volt battery will result in reduced 12-volt battery life." It also says to refer to the replacement number on the original battery label. The Hyundai IONIQ 5 manual (an electric car with a 12-volt battery) says: "Use batteries for replacement from an authorized HYUNDAI dealer." The Nissan Rogue 2024 extract we read names no required type, group size or CCA. We could not read Toyota, Honda, Ford, Tesla, BMW, Volkswagen, Mazda, Mercedes or Jeep manuals: their sites blocked us, did not load or asked for a vehicle number. That is a limit of this page, not evidence that those manuals say nothing.
What the battery makers say, and where they differ. The direction of the advice is the same everywhere: do not step down. The strength and the detail differ.
Two cautions. Clarios describes its own lab and fleet tests ("EFBs lost six times more water and lost 60% more capacity than AGM batteries") without a test name or test date (the page is dated 16 April 2021), so that is a marketing claim, not an independent result. And the makers who say an AGM can replace an EFB or a flooded battery (Clarios, East Penn) sell AGM batteries. The advice not to step down matches GM's manual, the one car-maker source we could read on it; the advice to step up is a seller's view and has a price: Interstate's AGM page says AGM batteries "can be more expensive (40–100% more than traditional batteries)." Interstate's own AGM article adds that certain start-stop cars that came with an EFB will not work with an AGM.
Gel is not the same as AGM, and chargers matter. BCI defines gel as electrolyte immobilized by a chemical agent, normally fine silica. Optima's blog warns that some chargers have confusing gel/AGM settings and advises avoiding any setting that references gel. GM's manual says to use a charger's AGM setting, if available, limiting the charge voltage to 14.8 volts; Interstate says to select AGM or Absorbed as the battery type. The three statements are not identical, so follow the instructions for your battery and your manual.
After the swap. East Penn's FAQ says hundreds of vehicle models require additional steps when a battery is replaced, from programming of windows, locks and sunroof to resetting engine and body control systems. VARTA adds that upgrading to AGM may require technical adjustments such as battery registration with the battery management system. We could not read a car maker's manual sentence about registration, so we state it only as the battery makers' view. Why the wrong type causes trouble is covered in car battery replacement cost.
Step three: cold cranking amps, and how much is enough
Cold cranking amps (CCA) is the most printed number on a battery and the most misread. BCI's glossary defines the rating as the discharge load in amperes that a new, fully charged and conditioned battery at -18 degrees C (0 degrees F) can continuously deliver for 30 seconds while holding a terminal voltage of at least 1.20 volts per cell, "7.2 V for a 12 V battery".
Three neighbours of CCA appear on the same labels. Cranking amps (CA) and marine cranking amps (MCA) are measured at 32 degrees F instead of 0; Interstate's glossary calls each an "artificially high rating" that "should not be confused with CCA". And a European (EN) rating exists too: BCI says "European standards (EN) also have a CCA rating defined somewhat differently. Numerically, the values tend to be similar, but they may not always be identical." The Hyundai IONIQ 5 label in the owner's manual prints both: 550 CCA by SAE and 440 A by EN, for the same battery. When you compare two batteries, compare the same rating.
How much do you need? The pages we read give the same first answer and then diverge.
- Interstate's page says the car maker typically recommends a CCA rating, and tells the reader to refer to the car manual, its battery finder or a trusted auto professional. It adds that batteries with higher CCA ratings "tend to be larger and heavier because they have more lead plates and electrolyte", so CCA often relates to size.
- In 2020 Optima told a boat owner to choose a battery that "meets or exceeds the engine manufacturer's requirements for cranking amps", but "there's no need to go overboard in that department." Optima's 22 September 2026 post, goes further, calling CCA "a bit of an antiquated form of measurement" because, in its words, most (not all) drivers will never encounter 0 degrees F.
- East Penn's FAQ asks whether the best batteries always have the highest CCA and answers: "No. Optimized power is not always reflected by CCA ratings."
Optima and East Penn sell AGM batteries, so weigh their view of CCA as a maker's view. The part that does not depend on that interest is what Interstate also says: take the car maker's number as the floor. We found no page that shows a benefit from a rating far above the floor beyond Interstate's advice that a higher rating is advisable in harsh winters. East Penn's 2012 warranty form excludes a battery "of an electrical size or capacity smaller than the one specified by the vehicle manufacturer."
A fair warning about the numbers on a shelf. CCA rises with price lines in some makers' tables and not in others. In Deka's spec sheet (effective 1 April 2026) the group 65 Gold battery is printed at 850 CCA and 24 suggested free months, the Ultimate at 750 CCA and 36 months, and the AGM Intimidator at 750 CCA and 40 months. A higher CCA sits on the lower-tier line there. The rating describes a 30-second starting test at 0 degrees F; it does not describe how long the battery will last.
Reserve capacity and amp hours: the number for a bad day
Reserve capacity (RC) is the second number on the label. BCI defines it as the number of minutes to reach 1.75 volts per cell when a new, fully charged battery at 26.7 degrees C (80 degrees F) is continuously discharged at 25 amperes. For a 12-volt battery that is the 10.5 volts Interstate names. In plain words it measures how long the battery can run the car's essential electrical load if the alternator stops charging. Interstate puts it this way: "Reserve capacity is the steady power your battery provides the electrical system when the alternator is not operating." Amp hours (Ah) express storage differently: BCI's example is 5 amperes for 20 hours, 100 amp-hours.
Why it matters more today than it once did is argued by Optima, again a seller: "batteries in many modern vehicles are put to the test more by how they are being discharged as they sit, than how hard they have to work to start the engine." East Penn's FAQ says: "The hardest scenario on a battery; however, is not using it at all."
The practical use is comparison inside one group size. The group 65 batteries in the tables later on this page print these reserve capacities: Interstate's 130, 130, 140, 150, 120 and 130 minutes across five lines (six batteries), Deka's 150, 140 and 150. The numbers differ by up to 30 minutes, and the order is not the order of CCA: Interstate's MTX-65 prints 750 CCA but 120 minutes, below the 130 minutes of the cheaper M-65 at 650 CCA. We found no maker that states a minimum reserve capacity for a given car; the car maker's label is the place to look.
The date code: how old is the battery you are buying
A battery starts to age on a shelf. Interstate's lifespan article says a car battery "could lose 5% of its charge sitting on a shelf" in a month and goes bad faster in hot weather if it is not recharged. East Penn's FAQ warns that batteries that sit for long periods can self-discharge to the point they cannot be recharged.
How to read it. Makers use different codes, and we could read only two.
- Interstate (FAQ): a two-character code stamped on the cover or on a label. "Letter - indicates in which month the battery was manufactured (Example: A is January, B is February, C is March, etc.)" and a digit indicates the year, for example 9 for 2019, 0 for 2020, 1 for 2021. The page's worked example is that a code starting with B1 means February 2021.
- Optima (blog dated 27 March 2026): the date code sits on a white 1 by 3 inch Non-Spillable label, usually on the side. "That label has a ten-digit serial number and the first four digits indicate the year and day of production," so a battery made on 27 March 2026 starts with 6086, the 86th day of 2026. Round stickers on the battery are inventory stickers that can be moved and have different meanings depending on the retailer.
We could not read date-code rules from Exide, Clarios, DieHard or Odyssey. The one shelf-age figure we found is Interstate's: a battery on the shelf older than six months "might start your car but it won't last as long under the hood." Our own advice, marked as ours: find the code before you pay and prefer the newest unit in the stack, because of that six-month figure. The code matters once more: Interstate's warranty says that without a receipt "your dealer will estimate your date of purchase from the manufacturer code on each battery." Keep the receipt either way.
The warranty: free replacement, discount periods and what they do not cover
Two kinds of warranty term appear on the pages we read, and the words differ by maker.
Free replacement is the period in which a battery that fails because of a defect is replaced without charge. Interstate's warranty document says: "Performance Warranty has a Free Replacement Period, and some battery models have an additional Discount Period." In the Discount Period, a failed battery lets the buyer purchase a replacement at a discounted price, a percentage off Interstate's suggested retail price. Optima's explanation of the older style, which it calls pro-ration, says a long-looking warranty is often "pro-rated, which means a consumer must pay a fee to have their battery replaced under warranty." Costco's page for Interstate-branded batteries calls its term a "36 Month Prorated Warranty" and tells the reader to check the duration printed on the battery's label. A long number on a shelf tag tells you nothing until you know how many of those months are free.
What the makers print, with the date of each sheet:
Rules that appear in more than one maker's warranty.
- The clock starts at purchase and a replacement does not restart it. Interstate: "Your replacement battery will not have any new or separate warranty coverage." DieHard: "When a battery is replaced during the 'Free Replacement Period', the warranty does not renew, it continues on from the original date of purchase." Optima: the coverage "doesn't re-set with each warranty replacement."
- Optima's 2021 blog says warranties are generally honored only by the retailer that sold the product; Interstate says it has a nationwide warranty, dealers estimate the purchase date from the code, and you do not need to take the battery back to the original location. So ask where a claim would be handled before you buy.
- Commercial use shortens the term. Interstate limits a battery in a commercial vehicle, a truck over one ton or a diesel (other than a passenger car or a personal pickup) to a one-year free replacement period, or two years for its MTZ model. DieHard warrants commercial-use vehicles for 90 days only. East Penn's sheet cuts the free period to 6 months (18 for its Intimidator AGM) for vehicles such as taxis and police cars.
- A merely discharged battery is generally not a defect. Interstate and East Penn (2012) exclude merely discharged batteries; DieHard says a battery within the warranty period found to be only in a state of discharge will be recharged at no cost.
- Claim labor is usually yours: Interstate says you may pay labor and installation charges, East Penn's 2012 form excludes them.
- East Penn's 2012 form excludes a battery smaller than the vehicle manufacturer specified: match the specification first.
Terms change, so an undated number is a risk. Interstate keeps separate warranty documents by purchase date; the one we quote applies to batteries purchased on or after 15 July 2026. DieHard's Platinum and Platinum AGM 4-year free replacement applies to batteries purchased on or after 1 March 2025. East Penn's older sheet (revision 1/25) and its April 2026 sheet print different suggested months for the same families, so we use the later one.
A last point about meaning. A warranty is a promise by the seller about what happens if the battery fails early, not a forecast of how long it will last. How long batteries last, and what shortens them, is a separate question that this page leaves to a separate guide; here the warranty is read only as a contract.
Which car battery warranty is best, and does PulsCar sell batteries? No warranty page we read compares its numbers with others, and the tabled terms run from 18 months of free replacement on Interstate's M line to 48 months on its MTZ line and DieHard's Platinum lines, with Duralast's consumer lines and Deka in between, Bosch's S6 AGM level with the top, and Duralast's shop-only AGM lines at 4 and 5 years. What differs most is the fine print: discount periods against free months, who honors the claim, commercial exclusions and the start date. PulsCar sells no batteries, and this page carries no affiliate links. We make an app that works with a car's diagnostic port, plus a free engine sound check. Neither tells you which battery to buy, so read the terms before the headline number, and keep the receipt and a photo of the date code.
The shortlist by situation: what each line's maker prints
This section is not a ranking and no line on it is our pick. It lists the lines whose makers printed something we could read on 5 November 2026, grouped by the situation the maker's page says the line is for, with numbers as printed. Claims such as longer life or better starting power are the makers' claims, and they are written that way.
The numbers that allow a direct comparison are on two groups, 65 and 48 (also sold as H6), because two makers print full tables for them: Interstate on its five car and truck product pages, and Deka on the East Penn spec sheet effective 1 April 2026. Other makers are absent because their own current pages printed no numbers for these groups in text we could read.
What the two tables show. Inside one maker's range the price ladder is steep and the rating ladder is not. Interstate's M-65 prints 650 CCA and 130 minutes of reserve capacity at a suggested price of $139.95 with 18 months of free replacement. The MTP-65 prints 750 CCA and 140 minutes at $224.95 with 30 months: $85 more for 100 more CCA, 10 more minutes and 12 more months. The AGM MTZ-65 prints 770 CCA and 130 minutes at $424.95 with 48 months, which is $285 above the M-65 and fewer reserve minutes than the MTP-65. In group 48, the M-48/H6 at $164.95 prints 690 CCA and 95 minutes, and the MT-48/H6 at $214.95 prints 640 CCA and 120 minutes: the dearer line has the lower CCA and the longer reserve. So CCA, reserve capacity, price and free months do not move together, and a buyer who optimizes one of them is guessing about the others. Deka's tables show the same pattern: in group 65 the Gold prints 850 CCA and 24 suggested months, and the Ultimate prints 750 CCA and 36.
A spec table is the maker's rating, not a result, and Interstate's warranty document warns that "the SRP may be different than the dealer's actual selling price".
Ordinary car, no start-stop, mild weather
The case: a conventional car whose maker specifies a flooded battery and which has no start-stop system. The cheaper lines suit this case, and the question is how long a warranty and how much margin above the specification you want to pay for.
If your car is a conventional one, a line that meets the car's group size and CCA at the lowest price is a legitimate choice; the printed difference is a shorter free-replacement period (18 months at the bottom of Interstate's range, 2 years at DieHard Silver and the base Duralast) and, in some lines, lower CCA or reserve capacity.
Start-stop and high-accessory cars: EFB and AGM lines
For a car that came with an EFB or an AGM, the shortlist begins with the type, not the price. The lines below are those whose makers describe them as for start-stop, high-demand or frequent-cycling use.
Two practical points. Interstate's MTX page says it is the right OE replacement "whether it came from the factory with an EFB battery or an AGM", and its part-number table marks the EFB parts with an -EFB suffix (24F, 47/H5 and 48/H6, at $259.95); check the part number you are given, because the page says its EFB is only suitable for cars that require an EFB. And longer-life claims are claims: Duralast says its Platinum AGM has "Two times the cycle life of conventional batteries" and DieHard says up to a 30% longer lifespan for its Platinum AGM; Duralast compares only with conventional batteries, DieHard prints no comparison, and neither prints how it was measured.
Hybrids and electric cars with a 12-volt battery. The US Department of Energy's page explains why this battery matters: in an electric drive vehicle the low-voltage auxiliary battery "provides electricity to start the car before the traction battery is engaged; it also powers vehicle accessories." Hyundai's IONIQ 5 manual says: "Use batteries for replacement from an authorized HYUNDAI dealer." Subaru's manual says that if the 12-volt battery is removed and installed, it may not be changed to EV driving, and that in that case the owner should contact a Subaru dealer. East Penn says it marks its Deka Intimidator AGM line with an EHP symbol, which stands for Electric Hybrid Performance, to reassure buyers. For your car, follow your manual first.
Cold climates
The cold is a CCA question and a state-of-charge question. Interstate's dealer-site FAQ says that in freezing temperatures a higher CCA level is required to crank the engine, and its MTP page describes that line as "high-cranking performance for cold to moderate climates", a maker's claim for a line that prints 750 CCA in group 65. The car maker's number is still the floor.
The less obvious cold risk is a discharged battery. Interstate's FAQ says a fully charged battery will not freeze until the temperature reaches approximately 75 degrees F below zero, while a discharged one can freeze at 15 degrees F; Nissan's manual says that if the battery is not fully charged in extremely cold weather its fluid may freeze and damage it. That is why short winter trips can hurt. Battery gas can explode: keep sparks, flames and smoking away from a battery, and never jump-start one that is frozen. Both the Nissan and Subaru manuals say not to jump-start a frozen battery.
Hot climates
Heat does the most damage, say East Penn and Hyundai. Interstate says batteries work best at 80 degrees F and that above 90 degrees F the chemistry "starts to degrade the sensitive components inside the car battery." East Penn says it is the heat that does most of the damage, but that more batteries actually fail when put to the test in the cold. Hyundai's owner page says the battery suffers most in hot climates because high temperatures can evaporate battery fluid.
Interstate says its MT line "offers the longest life in hot to moderate climates (of MTP/MT options)", which compares only its own two lines, and DieHard says its Platinum AGM "offers high-temperature performance". Both are claims with no test attached. Our observation, marked as ours: heat is a stress a rating cannot buy you out of, so the practical advice is a regular battery test and a tight hold-down.
Short trips and a car that sits
No maker we read sells a line only for this case, but the advice is consistent, and East Penn says its AGM tolerates infrequent use better. Hyundai's owner page says that if you take short trips often "you're not giving your battery enough time to fully recharge", and that infrequent use, with the vehicle parked for long periods, also passively drains the battery. East Penn says that frequent starting without enough time for the alternator to recharge is hard on a battery. Optima suggests looking more closely at the amp hour rating for a car that does not see regular use. In buying terms: compare reserve capacity inside the group, avoid batteries that have sat long on a shelf, and test the old battery and the charging system first; a new battery will not cure a drain (car battery keeps dying).
Vibration, performance cars and heavy accessories
Vibration is the cause Interstate calls most common: "Vibration is the most common way to kill a car battery." Interstate says AGM batteries have "a sponge-like resistance to vibrations." Hyundai's manual says: "Keep the battery securely mounted." If you drive a rough road or fit heavy accessories, check the hold-down before you check the brand.
Optima's product pages showed no text; what is readable is a retailer's copy: Les Schwab's page for the RedTop prints 720 to 800 cold cranking amps and a 36-month free replacement, and no price. Optima's 2021 blog says the RedTop is a starting-lighting-ignition battery, not designed for deep-cycle use. A Clarios press release dated 29 October 2026 says a RedTop with new hAGM+ technology was recently introduced, so older specs may not match what is on the shelf. Odyssey's US pages blocked us; the only Odyssey spec document we could read is a 2013 EnerSys datasheet (850 CCA and 130 minutes of reserve capacity for the 35-PC1400), which is 13 years old and is not today's terms.
Which car battery is best for a start-stop car or a hot climate, and does PulsCar have a favorite brand? The pages we read describe start-stop cars as needing an EFB or an AGM and warn against stepping down, and East Penn and Hyundai call heat the most damaging stress, but none of the maker pages we read ran a test that ranks one brand above another. PulsCar has no favorite and sells no batteries. We make an app that works with a car's diagnostic port and a free engine sound check; neither measures cranking amps or tells you which battery to buy. Use your car's group size and type, compare the printed reserve capacity and warranty terms, and keep the receipt. Check your own manual first: it is the authority for your car, and a counter's fit guide is a second check.
Prices: only what a page printed, with the date
Most big retailers blocked us or served pages without text, so there is no price table for them: AutoZone, O'Reilly, Advance Auto Parts, NAPA, Batteries Plus and Walmart blocked us, and Costco, Les Schwab, DieHard and Duralast printed no price. What we have is below, as read on 5 November 2026.
Our car battery replacement cost guide carries the installed price ladder and how the AGM choice moves the bill. One thing is worth repeating: the Ford dealer's fine print: "Taxes and installation extra." The sticker price and the price you pay are different numbers.
Independent testing: what exists, and what we could read
Consumer Reports tests car batteries in a lab and sells access to the results. Consumer Reports' page, titled "8 Best Car Batteries of 2026, Lab-Tested and Reviewed" and updated on 11 August 2026, says: "Consumer Reports tests more than 100 individual car batteries in our lab every year." It says it tests five units of each rated model, charges and discharges the batteries 180 times in a 167 degree F water bath to simulate under-hood temperature, puts them in a freezer to see how they perform at 0 degrees F, and tracks how long they last if the headlights are left on or the charging system fails. Its ratings cover overall score, cold weather performance, life and reserve capacity. The picks and the scores are behind a member wall, and we did not bypass it. The public part says: "Price doesn't necessarily mean better performance," in the words of Paolo Fu, who oversees car battery testing at Consumer Reports.
An older Consumer Reports article from 1 December 2015 describes its tests differently (15 weeks of cycling at about 167 degrees F, and a freezer test of whether a battery delivers half of its claimed CCA), so we keep the two descriptions apart and dated.
What the 2025 relays say, and the limit. Two media pages we could read relay Consumer Reports' best-in-group picks of 2025: Torque News (28 March 2025) and Jalopnik (12 May 2025). They name, by group: 24/24F X2Power SLI24FAGMDP; 35 Odyssey Extreme 35-PC1400T; 47 Duralast Platinum AGM 47 H5-AGM; 48 Odyssey Performance 48-720; 49 ACDelco 49 AGM; 51R Super Start Platinum AGM 51R-51RPLT; and 65 Super Start Platinum AGM 65PLT. Neither page ran its own test, and they reach us second-hand, and the 2026 page lists an eighth group, 94R, that they do not cover. They also carry a lesson. A January 2026 Jalopnik article relaying the lowest-rated batteries names the Duralast Platinum AGM 51R-AGM among them and says, of Consumer Reports' test, that the Duralast "performed well in the Cold Weather category, but it did poorly when it came to overall life and reserve capacity." The same product line appears on a 2025 best list in one size and a 2026 lowest list in another. A rating belongs to a model, not to a brand.
Other sources. AAA says its AAA Premium Battery, sold through NAPA, "undergoes periodic quality testing at independent certified labs"; the release names no lab and prints no test results. We found no US government test of retail car batteries, and we did not locate readable roundups from Car and Driver, Popular Mechanics, Wirecutter, MotorTrend, Edmunds or J.D. Power, so we say nothing about them.
Is there an independent test of car batteries, and has PulsCar run one? Consumer Reports says it tests more than 100 batteries a year in its lab, and its public page describes the cycling, cold and reserve tests, but the ratings are available to members only, and the free 2025 relays we could read show that ratings are given per model rather than per brand. PulsCar has run no battery test, and nothing on this page is a PulsCar rating. We make an app for a car's diagnostic port and a free engine sound check, and we sell no batteries. If an independent rating matters to you, read the member page for your group size, and compare it with the printed specs and terms on this page. Until then, the printed specs are all we can responsibly compare.
Brand by brand: what we could read and what we could not
A buyer searching for the best car battery brand wants one name. We cannot give you one. Our tie-breaker, marked as ours: among batteries that match your group, terminal side, type and CCA, take the freshest date code from a seller whose claim you can make near you, then compare free-replacement months. The table shows what we could read about each name on 5 November 2026.
Before you buy: is it really the battery?
A new battery is the wrong purchase when the old one is fine. Hyundai's IONIQ 5 manual gives a first cheap check: "Turn on the interior light. If the light dims or goes out when you operate the starter, the 12V battery is drained." Drained is not dead: a charging fault or a drain will flatten a new battery as it did the old one. Our how to test a car battery guide covers the tests step by step and when the alternator is the real problem, and car battery keeps dying covers a drain that returns.
Test first, buy second.
Fitting it safely, and what happens to the old one
The makers print serious warnings, and they are not softened here. Battery gas can explode: keep sparks, flames and smoking away from a battery, and never jump-start one that is frozen. Nissan's manual says "Explosive hydrogen gas is always present in the vicinity of the battery." Subaru's manual says that batteries "give off a gas which is highly flammable and explosive." GM's manual adds that they contain acid that can burn you. Interstate's dealer-site FAQ adds that batteries release hydrogen as they charge, so charge in a ventilated area.
Before you disconnect, and resets after. GM's manual says that before disconnecting the negative battery cable you should turn off all features, turn the ignition off and remove the key if equipped, because if this is not done "you or others could be injured, and the vehicle could be damaged." After the swap, East Penn says hundreds of models require additional steps, such as window, lock and sunroof programming and resetting engine and body control systems. Read your own manual's battery section before disconnecting anything.
The old battery is worth money, and it must not go in the trash. BCI explains the core charge: "A core charge is a form of deposit paid when you purchase a battery and is refunded to you when the battery is returned." BCI says retailers can charge one in all 50 states and that it is required by law in over 30. The US Environmental Protection Agency's advice is to return lead-acid batteries to a battery retailer or a local household hazardous waste collection program and not to put them in the trash or municipal recycling bins; it says they may contain up to 18 pounds of lead and about one gallon of corrosive sulfuric acid.
The traps: three ways a careful buyer still gets it wrong
Trap one: buying the biggest number. Optima says more CCA is not necessarily better, and the tables above show a cheaper line printing more CCA than the one above it. The defense: write down the original group size, type and CCA before you walk in, treat them as the floor, then compare reserve capacity inside the group.
Trap two: stepping down a type, or stepping up without checking. GM's manual says a standard battery in a Stop/Start truck will result in reduced battery life; Interstate says an EFB will not work in a start-stop vehicle designed for an AGM; VARTA says downgrading from AGM to EFB is not recommended. In the other direction, Clarios and East Penn say AGM can replace EFB or flooded, but Interstate says some EFB cars will not accept an AGM and VARTA adds that the swap may require registration with the battery management system, and East Penn lists resets that hundreds of models need. The defense: keep the type, or step up only after reading your manual or asking a dealer about registration.
Trap three: reading months as quality and ignoring the clock. A 4-year free replacement and a 36-month prorated warranty are different promises. The term starts at the purchase date, a replacement does not restart it, commercial use cuts it, and without a receipt the dealer may estimate the start from the date code. The defense: keep the receipt, photograph the date code at the counter, and ask who honors a claim.
Three composite situations, decoded
These are composite scenarios, not individual customers. The details are illustrative.
Situation one: the start-stop SUV and the counter offer. An owner's battery dies and the counter offers a cheaper flooded battery of the same group size. The owner reads the old battery's label and the manual, finds the car has start-stop, and asks for an EFB or an AGM of the same group, whichever the label says. Lesson: a battery that fits the tray is not necessarily a battery the car was built for; the type is the question to ask.
Situation two: the commuter with short trips and a hot summer. A driver's second battery died at under three years. Before buying a third, they have the charging system tested, because a new battery will meet the same short trips and heat. They take the group and type from the old label, compare the reserve capacity of two batteries in that group, photograph the date code and keep the receipt. Lesson: the cause of an early death can outlast the battery, so test before you buy, and compare the number that matters on a bad day.
Situation three: the older car on a budget. An owner of an eleven-year-old car without start-stop is choosing between two lines of one maker in the same group. One prints 650 CCA, 130 minutes of reserve and 18 months of free replacement; the other, $70 more, prints 675 CCA, the same 130 minutes and 24 months. The owner plans to keep the car two more years, asks how a claim would be handled, and picks the one that meets the car's specification and whose warranty they would use. Lesson: when the specs are close, the decision is the warranty terms and how long you will own the car, and the printed figures can be compared directly.
Where a free sound check fits, and where it does not
This is our side of the page, and it concerns a free PulsCar product. PulsCar's free sound check asks you to film your engine running for 30 seconds and returns a report by email in about ten minutes. The home page states the terms plainly: "No payment, no card, no subscription." If a clip cannot support a confident verdict, the report says "inconclusive" and you can record again.
It has no part in choosing a battery. It listens to a running engine; it does not measure battery voltage, cranking amps or the charging system, so it cannot tell you whether your battery is weak or which one to buy. Where it may help is after a new battery goes in: if the car still has an engine noise you cannot place, a short clip is a free second opinion. A sound that only appears while braking or turning may not be in a clip filmed at the engine, and a noise from the brakes, the steering or a wheel, or any red or flashing warning light, means inspect first: pull over safely, switch the engine off, and have the car checked before you drive it on.
Film 30 seconds of the engine running on your phone. PulsCar returns a free report by email, or says it is inconclusive. It does not test batteries, and a noise from the brakes, the steering or a wheel, or any red or flashing warning light, means inspect first: pull over safely, switch the engine off, and have the car checked before you drive it on. Free, no card, no subscription.
What this page cannot tell you
The limits of this page are as real as its sources.
- No testing of our own, and no ranking. We did not buy, test or install any battery. Performance statements are a maker's claim or a rating, labeled that way. We found no independent test we could read in full: Consumer Reports' ratings are behind a member wall, and the free relays are from 2025 and January 2026.
- Many big retailers unread. AutoZone, O'Reilly, Advance Auto Parts, NAPA, Batteries Plus and Ford and Walmart blocked us, so EverStart, Super Start, Legend, Motorcraft and other house brands have no specs here.
- Missing maker documents. We could not read current Odyssey, Exide, ACDelco or Optima product and warranty pages, or DieHard, Duralast and Bosch specs. A 2013 Odyssey sheet and a 2017 Exide sheet are old and are not used as current terms.
- Few owner's manuals. We read the GM, Hyundai, Subaru and Nissan manuals. Toyota, Honda, Ford, Tesla, BMW, Volkswagen, Mazda, Mercedes and Jeep manuals were blocked or gated. Your own manual is the authority for your car.
- Thin rules on dates and standards. We could read Interstate's and Optima's date codes only, and the one shelf-age figure is an Interstate article's. We did not have the texts of SAE J537, EN 50342 or DIN, and we found no state fee schedule.
- Prices and terms change. Every figure is as printed on 5 November 2026.
Your action plan: before you go, at the counter, after
Before you go
- Test the old battery and the charging system first; see how to test a car battery.
- Write down, from the old battery's label and your manual, the BCI group size, the type (flooded, EFB or AGM) and the CCA the car maker specifies.
- Find out whether your car has start-stop and which type it shipped with. If the old label does not print EFB or AGM, or the battery may not be original, use your manual's battery section or the store's fit guide, not the battery that was in the car. Makers say a start-stop car takes an EFB or an AGM.
At the counter
- Ask for the exact group (99 and 99R put the posts on opposite sides), type and CCA, and look at the date code on the case before you accept the unit. Photograph it.
- Compare reserve capacity between batteries of the same group, not CCA across groups.
- Ask the warranty questions: how many months are free, is there a discount period, where is a claim handled, what starts the clock, and what excludes it.
- Ask whether the price includes installation, taxes, a core charge and any battery registration your car needs; Ford's dealer fine print said taxes and installation were extra.
After
- Keep the receipt with the date code photo. Follow your manual's order for disconnecting and any resets.
- Battery gas can explode: keep sparks, flames and smoking away from a battery, and never jump-start one that is frozen.
- Return the old battery to the retailer or a household hazardous waste collection point, not to the trash.
- If the new battery dies early, start with the charging system and a drain test, and read the warranty before assuming the battery was defective.
Sources and documents
The facts on this page come from the pages below, read on 5 November 2026 and saved as text, except where a date is given; advice marked as ours is ours. Prices, ratings and warranty terms are as printed that day, on the sheet dates named in the text.
- Battery Council International (BCI): BCI Group Sizes and the group size tables PDF; vehicle battery replacement data; battery terms glossary; common and alternative battery chemistries, 18 February 2025; how to recycle a lead battery
- Interstate Batteries: product pages M, MT, MTP, MTX and MTZ; EFB batteries and AGM batteries; warranty page and the warranty for batteries purchased 15 July 2026 or later; FAQs, FAQs on a dealer site and glossary; articles on CCA, battery lifespan, why a battery dies, what an AGM battery is and charging an AGM
- East Penn (Deka): SLI spec sheet effective 1 April 2026; automotive spec sheet, revision 1/25; FAQs; warranty sheet; electric and hybrid vehicle battery section
- Clarios and VARTA: Clarios on AGM batteries for start-stop vehicles; Clarios blog on AGM; Clarios hAGM release, 29 October 2026; VARTA, EFB technology and batteries for start-stop systems (Europe site)
- Other makers and sellers: DieHard, warranty PDF; Duralast, batteries; Bosch, batteries; Optima blog posts on warranty, cold cranking amps, questions, the date code and whether AGM is worth the money; Les Schwab, RedTop; Costco, automotive batteries; EnerSys, Odyssey datasheet, August 2013 (old; not used as current terms); Ricart Ford, Motorcraft MAX offer
- Car makers' owner's materials: GM, 2026 Chevrolet Silverado 1500 owner's manual; Hyundai, 2023 IONIQ 5 owner's manual and extending battery life; Nissan, 2024 Rogue owner's manual; Subaru, owner's manual
- Independent and consumer sources: Consumer Reports, 8 best car batteries of 2026 (public part only) and car batteries: which ones do best, 1 December 2015; Torque News, Consumer Reports best car batteries 2025, 28 March 2025; Jalopnik, best car batteries, 12 May 2025 and lowest-rated car batteries, 17 January 2026; AAA, NAPA and AAA battery release, 9 May 2022 and a regional club's mobile battery service page
- Government: US Department of Energy, Alternative Fuels Data Center, how hybrid electric cars work; US Environmental Protection Agency, used household batteries
- PulsCar: home page and free sound check
- Attempted, access blocked, not quoted: AutoZone, O'Reilly Auto Parts, Advance Auto Parts, NAPA and Batteries Plus product pages, Ford and Motorcraft pages, Mopar and Toyota parts, and Odyssey's US site; Walmart; Optima's product, FAQ and warranty pages (showed no text); the member ratings on the Consumer Reports pages; Toyota, Honda, Ford, Tesla, BMW, Volkswagen, Mazda, Mercedes and Jeep owner's manuals
Prices verified 5 November 2026: every price, range and fee above is as printed on the pages listed in Sources that day. Technical documents verified 5 November 2026: standards-body pages, maker pages, owner's manuals, government pages and warranty documents. Written by PulsCar, which makes an app for a car's diagnostic port and the free sound check.
