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Does standing with the air conditioning on hurt the battery?

  • 16/07/2025

Over the past few days of high temperatures, we've received several inquiries about whether idling with the air conditioning on can damage a car's battery. FQS Battery We give you the answer.

Being stopped with the engine running and the air conditioning on does not directly damage the starter battery, but yes it can accelerate its wear under certain conditions. Here's why:

Normal Situation
  • While the engine is running, the alternator supplies power to both the air conditioning and the rest of the electrical systems.
  • Under normal conditions, this is sufficient to keep the battery charged.
Alternator working at its limit
  • In modern vehicles with numerous active devices (screens, USB ports, chargers, etc.), the alternator may not be able to generate enough power if all of these systems are running while the car is stopped.
  • In older vehicles, although there is less fuel consumption, the charging system is often less efficient. Therefore, the result can be the same: insufficient charge for the battery.
  • Furthermore, when the car is idling, the alternator spins at lower rpm, further reducing its charging capacity.
Heat, silent enemy
  • Standing still with the air conditioning on significantly raises the temperature in the engine compartment.
  • Heat is one of the factors that most negatively affects battery life, especially in conventional and EFB batteries.
  • This excess temperature can accelerate electrolyte evaporation, deteriorate the internal plates, and reduce overall battery performance.
Short journeys + long idling stops + air conditioning: a dangerous combination
  • If you only use your car for short trips and often sit idly with the engine running and the air conditioning on, the battery doesn't have enough time to fully recharge.
  • This situation causes premature sulfation of the plates, which results in loss of capacity and a shortened lifespan.
Conclusion

Standing still with the air conditioning on does not pose a direct risk for the battery, provided that:

  • The battery is in good condition.
  • The charging system (alternator and regulator) is working properly.
  • Regular journeys are made that are long enough to allow for a full recharge.
Recommendations
  • Minimize long periods of idling with the air conditioning on as much as possible.
  • Take long trips (at least 35-40 minutes) frequently to ensure proper battery charging.
  • Regularly check the battery's condition and charge level. If necessary, recharge it with a suitable charger.
Using the multimeter on an FQS Battery AGM battery

FQS Battery Chargers and Testers

120v
120V charger  
HIGH FREQUENCY CHARGER 12/24V 20 AMP.
105v
105V charger  
HIGH FREQUENCY LITHIUM CHARGER INCLUDED
bcsmart5000
BC SMART 5000  
CHARGER FOR 3 TO 150AH LEAD-ACID/MF/AGM/GEL BATTERIES
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12V/24V SMART CHARGER/STABILIZER. 10-STAGE CHARGING
205v
205V  
OBD Memory Saver - Memory Saver

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