Symptoms
A shorter electric-only range than expected, a state of charge that swings between extremes, a fan audibly running hard, or a hybrid system warning.
Likely cause
Cells age with time, cycles and heat. A blocked cooling intake raises operating temperature. The filter or duct is a maintenance item on many hybrids and is frequently never touched.
How should it be checked?
Find the cooling intake and check whether it is clear. On a used hybrid, ask whether the pack has ever been tested or had cells replaced.
How can you check it yourself?
Locate the battery cooling vent — commonly beside or under a rear seat — and check it is not blocked by luggage, a seat cover or dust.
The question to ask the shop
Has the hybrid battery been tested, what did the block voltages read, and has the cooling filter ever been cleaned or replaced?