Toyota Prius Battery: Specs, Fitment & Common Faults

A genuinely significant, widespread issue on hybrids: Toyota's own dealer test may not let the battery stabilise before checking it — plus official Ready-mode guidance worth following.

Illustration for editorial purposes

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OEM Part Number: 28800-YZZPD

Genuinely important to know: this covers the small 12V auxiliary battery only, genuinely shared with the Auris Hybrid and Lexus CT200h given the common hybrid platform — completely separate from the large hybrid drive battery, which is a different, much more expensive component.

2004-2015, genuine reference (shared with Auris Hybrid, Prius+/Alpha, Lexus CT200h)	Toyota OEM: 28800-YZZPD — S46B24R, 45Ah
Important	Even with the vehicle off and locked, the alarm and electrical system stay connected to this battery and will drain it over time if the car sits unused.

A Genuinely Significant, Widespread Issue Worth Understanding on Hybrid Models — Toyota Prius Battery

If your hybrid's 12V battery keeps reading low despite a dealer telling you it "passed all checks," this is genuinely worth knowing: real, documented owner reports suggest Toyota's own dealer diagnostic test doesn't allow the battery sufficient time to stabilise after charging before testing it — meaning a genuinely weak battery can pass, only for the voltage to drop again within hours. It's worth understanding why hybrids are more prone to this: since the hybrid powertrain doesn't use the 12V battery for traditional engine cranking, manufacturers fit a considerably smaller-capacity battery, adequate for its job but with less margin for short journeys or extended standing.

Genuinely useful, official Toyota guidance worth following: if the car will be sitting unused for more than a few days, Toyota's own recommendation is to run it in "Ready" mode for around an hour a week. It's also genuinely important to avoid leaving the car in "Accessory" mode, since this can flatten the 12V battery within just a few minutes on some examples.

If the problem is genuinely persistent, it's worth pushing for a proper cell-level health check rather than accepting a simple charge-and-return: one documented case saw Toyota's own diagnostics find genuinely damaged cells, resolved with a warranty replacement using a higher-capacity unit, after which the problem stopped entirely.

Toyota Prius Battery: The Part Everyone Blames First, Not Always Correctly

Ask anyone why their Toyota Prius won't start and "the battery" is usually the first guess, and it's frequently correct, which makes it a reasonable starting point. It's not always right, though, so it's worth ruling out other causes before spending on a replacement that changes nothing.

Before you buy: battery size, capacity and type (standard vs AGM/EFB for stop-start systems) vary by trim and engine. Always confirm against your VIN before ordering.

Toyota Prius Battery: What It Does

On the Toyota Prius, powering the engine start and running electrics while the engine's stopped both fall to the 12V battery. Stop-start technology puts significantly more strain on it than older designs, thanks to how frequently the engine cycles — explaining why a specific AGM or EFB battery is needed rather than a standard unit.

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Toyota Prius Battery: Warning Signs, DIY Difficulty & Aftermarket Advice

These are the same regardless of make or model — see our full Battery Guide for warning signs to watch for, confirming fitment against your VIN, and matching the right technology (standard, EFB, AGM) when buying aftermarket.

More Toyota Battery

The same part, covered across other Toyota models.