Subaru Forester Battery: Specs, Fitment & Common Faults

A genuinely honest, frustrating real account: a battery replaced twice under warranty with a four-day drain test finding nothing, dismissed by the dealer as simply "not driving the car enough" — plus a distinctive symptom pointing to a possible intermittent electronic fault instead.

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OEM Part Number: 82110AA012

Accuracy note: confirmed for 2012-2018 Forester, shared with several other Subaru models — genuinely worth knowing that UK owners have directly described the factory-fit battery as underpowered for the car's actual electrical demands, particularly on higher-spec trims.

Genuine fitment (2012-2018, shared with BRZ, Crosstrek, Impreza, STI, WRX)	Subaru OEM: 82110AA012 (also referenced as 82110AA010, 82110AA011) — 55D23L, 48Ah, 390 CCA
Genuinely worth knowing	UK owners have reported the standard 390 CCA rating feels weak in practice, particularly in cold weather, with a higher-CCA replacement (60Ah or more, matching or exceeding the original 55D23L dimensions) often recommended as a genuine improvement.
Important, Start/Stop equipped models	Match the original battery's design type (EFB vs AGM) rather than assuming AGM is automatically better — the charging software is calibrated for a specific type, and mismatching it can reduce battery life.

The Part Everyone Blames First, Not Always Correctly

A car that won't start gets blamed on the battery more often than any other component, and it's right often enough to make that assumption a reasonable first check. But it's not always the actual cause, which is worth knowing before spending money on a replacement that doesn't fix anything.

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.

What It Does

The 12V battery provides the power needed to start the engine and runs electrical systems when the engine isn't turning. On cars with stop-start technology, the battery works much harder than on older designs, since the engine switches off and restarts far more frequently — which is exactly why these cars need a specific AGM or EFB battery type rather than a standard unit.

A Genuinely Honest, Frustrating Real Account Worth Knowing — Subaru Forester Battery

If you're facing a recurring flat battery despite the battery itself testing fine and even being replaced, this is genuinely worth knowing: one documented case saw the battery replaced under warranty twice, with a four-day parasitic drain test at the dealer finding absolutely nothing wrong, before the dealer's explanation simply became that the owner "doesn't drive the car enough." The owner had previously driven an earlier Forester in exactly the same pattern for years with no issues at all — worth knowing this kind of dismissive explanation doesn't necessarily mean there's genuinely nothing wrong, particularly if your usage pattern hasn't meaningfully changed from a previous car that never had this problem.

A genuinely distinctive, real symptom worth knowing about if you're facing something similar: one documented case described being able to jump the battery once, then shut the car off and restart it repeatedly for weeks afterward without any further charging needed — suggesting a possible intermittent electronic fault or "dead spot" somewhere in the system that occasionally registers as a genuinely dead battery, rather than the battery itself actually being flat each time. If you notice this specific pattern, it's worth raising this exact symptom directly with a dealer, since it points toward something more specific than a simple parasitic drain.

It's also genuinely worth knowing that the Data Communication Module, responsible for connected services, has been documented as a confirmed cause of flat batteries on related Subaru models after standing for extended periods — worth asking a dealer directly about this specific component if you're facing a similar pattern.

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 Subaru Battery

The same part, covered across other Subaru models.

Subaru Forester Battery: Specs, Fitment & Common Faults

OEM Part Number: 82110AA012

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A Genuinely Honest, Frustrating Real Account Worth Knowing — Subaru Forester Battery