Crews from Cosham fire station were called to the scene eastbound at 6.02pm on Thursday.
When they arrived they found a car’s battery had caught alight.
Two appliances were sent and officers left at 6.50pm. Nobody was injured.
Crews were then called out at 10pm to the A27 eastbound, just before the A3(M) split, to a Vauxhall Astra which had caught light.
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The fire had started in the car’s engine compartment.
The male driver was uninjured and had pulled over to the hard shoulder on the eastbound carriageway.
Crews from Havant and Cosham fire stations put out the fire by 10.45pm.