How We Calculate

Data rules

• No invented numbers. A value we can't source is left blank and the tool shows "we're still checking" or hides the option.
• Official sources are preferred. Third-party figures appear as ranges, labelled.
• Each result shows its sources and check dates. A script warns about any value older than six months.

Car battery replacement cost calculator

For the store you pick, we take the sourced battery price range and the sourced installation range. Low adds the low ends, high adds the high ends. Typical sits at a point in the battery range that depends on type (a modelling assumption, not market data):

• FLOODED: lower half of the range
• EFB: upper half of the range
• AGM: upper end of the range
• UNSURE: middle of the range

Installation uses the middle of its range. We then add fees we can source (California's $2), subtract a core refund only where a core charge is sourced, and leave out battery registration or coding because we have no sourced fee. Start-stop cars are priced as AGM, since a flooded battery is not a valid replacement. Vehicle type does not change the price, as we have no sourced data splitting prices by size.

EV and hybrid calculators

We check the warranty first: covered if your age is within the years and your miles are within the limit. Custom EV packs multiply your kWh by an installed per-kWh range derived from sourced model data. We never use BloombergNEF pack prices as a retail rate.

Voltage checker

Resting bands come from OPTIMA Batteries' published guidance: about 12.6V or more is a full charge, charge when it rests below about 12.4V, and a healthy battery should not rest below about 12.0V. OPTIMA makes AGM batteries; we apply the same bands to flooded batteries until we add a flooded-battery maker source. Cranking (about 9.6V minimum) and charging (typically 13.7V to 14.7V) are build-brief starting points we are still verifying. We show no state-of-charge percentages because we have no sourced table.

Other tools

• Battery life estimator: AAA's roughly three to five years, split by climate (hot about 3, cool 5 or more). Mild at 4 years is our midpoint assumption. Wear factors add caution but never change the years.
• Group size finder: case dimensions from a third-party BCI guide; the match tolerance is our default. Not a vehicle lookup.
• CCA calculator: a rule of thumb of about 1 CCA per cubic inch for petrol and 2 for diesel (1 L = 61.02 cubic inches). Not a maker spec.
• Charging time: hours ≈ Ah × (1 − charge) ÷ amps × 1.2.
• Warranty calculator: credit = price × remaining months ÷ total months after the free period. Retailer terms vary.
• DIY savings: your inputs only; no market data.

What we leave out

We do not convert US prices into other currencies. Other countries get their own pages once we have local price data.