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You’ve probably heard that draining a car battery flat can lead the battery to die prematurely. Can leaving the interior lights too cause the battery to die?
Read on to find out if indeed they can, how long the battery lasts, and for tips to get the car battery to last longer.
Does a Dome Light Drain a Car Battery?
Yes, a car interior dome light can drain the battery flat.
LED Lights and Battery Drain
Yes, the interior LED lights can drain the battery flat albeit slower than the filament bulbs. Over time, the battery can be drained flat.
Will Leaving the Car Interior Light on Kill the Battery?
Not necessarily. It depends on the type of interior light, the charge level of the battery, and even how old the battery is. An older, aged partially battery that is on its last legs may die if the interior lights are left on.
More so, if the lights have older filament bulbs instead of the LED type. A fully charged battery in good condition is more likely to survive. Note that frequent deep discharges can shorten the battery life!
Fortunately, in newer car models, the lights may automatically be switched off after a preset time when you remove the ignition key to avoid the deep and damaging discharge of the battery.
Car Interior Light Draining Faster than Usual? What to Check
While leaving the interior dome light on will eventually drain the car battery flat, the interior light can drain flat faster than usual. Should this happen, check the following:
1. Is the car battery charging fully? A partially discharged car battery will drain faster with the interior light left on. The battery might be charging fully if:
- There’s corrosion on the battery posts
- the positive, negative, and ground cable connections from the battery are loose or damaged
- the alternator is failing.
You may also be interested in: Why the Car Alternator Output Voltage may be Low (How to Check)
2. The car battery is aging and losing its capacity to hold charge. An aging or damaged battery’s charge level drops quickly even when it has been fully charged.
Here is a quick test you can do.
- Charge the battery fully and check how long the headlamps can light before they dim.
- Depending on the reserve capacity of the battery, the runtime can be anywhere from 60 – 90 minutes. If it is significantly lower say 30-45 minutes then there is a high chance that the battery has lost some of its capacity.
You can also have the car battery tested at an auto repair shop.
How Long an Interior Car Light Stays On Before a Battery Dies
This depends on the power consumption of the bulb type used in the interior dome light. A 4-watt interior light can burn for about 3.5 days and only draw a fully charged 55 Ah car battery to 50% of its capacity.
An 8-watt dome light can last for about 1.7 hours (estimated) with the same capacity.
Tips to Get the Interior Lights Lasting Longer
To get the interior dome lights to last longer:
1. Replace the interior light bulbs with LED light modules if not already using them. They are brighter and consume significantly less power (50% or more) than filament light bulbs.
2. Are the dome interior lights set to permanently on mode or auto (usually) the middle position switch? If the light selector switch position is set to ON, then the interior light will stay on draining the battery even when the ignition key is removed.
3. Consider installing a battery saver or low voltage disconnect switch that protects the car battery from damaging deep discharges.
Always be Prepared
Lastly, it never hurts to be prepared, always keep a set of jumper cables or a portable jumpstarter pack in the car to get you back on the road in the event that the battery is drained flat.
Closing Thoughts
Yes, car dome lights can drain the battery. LED lights too albeit slower. How long the battery lasts depends on the power consumption of the bulbs used, how many they are, whether the battery is fully charged or not, and if it is still in good condition.
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