Signs of a failing hybrid pack

These symptoms do not confirm a battery fault, but each warrants a professional inspection:

• The car sat for a long time and now will not charge or go into "ready" mode.
• A hybrid system or battery warning light comes on.
• Fuel economy drops noticeably.
• The battery gauge swings quickly from full to empty.
• The gas engine runs more than it used to, or the car feels weaker accelerating.
• The battery cooling fan runs a lot.

Do not assume the worst

In EVTU's experience, the BMS electronics themselves rarely fail. The usual culprit is low or drifted module voltages, which can often be corrected on the bench. A diagnosis tells you which it is before you spend money on a new battery.