P0C30: Hybrid/EV Battery Pack State of Charge High
What to do
Expect regenerative braking to be weak or absent, which means the car will not slow as sharply as usual when you lift off — leave more room and expect to use the brake pedal more until it is fixed. If it appeared after a long descent on a full battery, that may be honest behaviour rather than a fault. Otherwise the two candidates are a charging fault or a current sensor that has drifted, and the second is much cheaper — ask which was checked.
What this code means
The traction battery is holding more charge than the module believes it should.
A battery being too full sounds like good news and is not, for the same reason at P0B26: the top of a lithium pack's range is where damage happens, and the headroom the module normally keeps is what stops regenerative braking pushing it over.
Two readings, and they need separating because they lead opposite ways. The pack really is too full — a charging control fault, or repeated regeneration with nowhere to put the energy, which a long mountain descent on a full battery produces honestly. Or the counting is wrong: state of charge is integrated from current rather than measured, so a drifting current sensor makes the module believe in charge that is not there. That is the P0B0E family, and P0B13's correlation check is what catches it.
The consequence the driver actually notices is worth stating plainly, because it changes how the car behaves in traffic. With no room to absorb energy, regenerative braking is reduced or withdrawn. On a car that normally slows firmly the moment you lift off, that pedal-feel simply disappears — one-pedal driving becomes coasting, and the friction brakes have to do work the driver is used to the motor doing. It is not dangerous if you know about it, and it is a genuine surprise if you do not.
Likely causes
Start here
- Faulty battery current sensor · specialist
Less common
- Charging system overvoltage · specialist
- Faulty battery energy control module · specialist
- Faulty battery pack sensor module · specialist
- Weak or failed cell group in the battery pack · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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