Battery drain problems are common in most BMW models. Besides, this issue can be nagging if it happens at the wrong time and place, such as in a public park or when you need the car the most. If the battery is completely drained, you might be forced to recharge it before cranking the engine.
Some of the things that cause battery drain in a BMW are plugged in external devices, extreme weather, old battery, faulty alternator, faulty final stage resistor, taking many short drives, BMW Intelligent Battery Sensor, and plugged in OBD-II diagnostic scanner.
What causes the BMW battery to drain?
Plugged in external devices
The main reason why your BMW battery drains faster is because of plugged-in external devices. Since cars use an alternator, a gadget that recharges the battery while the car is running, the battery doesn’t drain faster when running as it recharges.
But when the engine is turned off, the battery will drain faster as it won’t be recharging. The plugged-in devices will only draw power from the battery and nothing will recharge the battery. That’s why leaving your headlights on after parking your car can drain the battery faster.
So, before you turn off the ignition, ensure there are no adapters or chargers in the cigarette outlet.
Extreme weather
If you live in areas with extreme weather conditions, the weather may also have an impact on how the battery performs. Extreme winter or hot summer days can cause your battery to drain faster. It is also important to note that newer batteries provide more resistance to extreme weather conditions compared to old batteries.
Old batteries could perform poorly or die completely in extreme cold or hot weather. That’s why it is vital to install a reliable and durable battery for your BMW.
Plugged in OBD2 diagnostic scanner
An OBD2 scanner helps to diagnose issues when the check engine light comes on. Nonetheless, even though this tool is vital, it is not a good idea to leave it plugged in the car overnight or for long periods. Besides, the OBD2 diagnostic scanner utilizes more battery power when the car is idle than when it is running.
When you’re diagnosing your car, ensure to use the OBD2 scan tool when the car is running and not at idle to save battery power.
Faulty alternator
As mentioned earlier, an alternator is a gadget that recharges the battery while the car is running. Therefore, if the alternator is faulty or not working as intended, it won’t charge your BMW’s battery effectively. If you have a faulty alternator, you should replace it before resorting to buying a new battery.
BMW Intelligent Battery Sensor
The BMW Intelligent Battery Sensor (IBS) is a device attached to the battery negative terminal. This device features a microprocessor that monitors different battery conditions, such as current, starting current, closed-circuit current, voltage, and temperature.
The IBS can be found in the BMW 3-Series (E90/E91/E92/E93) and the 5-Series (E60/E61). When the car is parked or turned off, the IBS uses a lot of power that ends up draining the battery. This is because it rises every few seconds and goes back to sleep to prevent loss of power.
Old battery
Whether you have got a new or old BMW model, the lifespan of a BMW battery is between 3 and 5 years. What’s more, newer batteries hold up well against the elements than older ones. So, the older your car’s battery is the less efficient the battery will be. If your battery is draining very fast, it might be an indication that the battery is very old and needs replacement.
Taking many short drives
Starting your BMW engine takes a lot of power from your car’s battery. But since the alternator recharges the battery when the car is running, a lot of power is retained. However, if you frequently take short drives, the alternator may not have enough time to properly recharge the battery. After some time, this will shorten your BMW’s battery lifespan.
Faulty final stage resistor
Owners of the BMW E39, E46, and E53 have had multiple battery draining issues because of a faulty final-stage resistor, also referred to as the infamous “Hedgehog.” Some BMW users refer to it as a heater fan resistor or blower motor resistor. Take the car to a BMW service center and have the faulty final stage resistor replaced.
FAQ
What is the BMW Intelligent Battery Sensor?
The BMW Intelligent Battery Sensor, also referred to as IBS comes with a microprocessor that monitors different battery conditions, such as temperature, voltage, current, starting current, and closed-circuit current.
When the car is running, the IBS is constantly active and monitoring different battery conditions. But when the car is parked, the IBS arises every few seconds, conducts the tests, and goes back into sleep to help preserve battery power.
How do I fix BMW battery drain problems?
First and foremost, you will have to identify the problem that is causing the battery to drain. Nonetheless, some of the things that you can do to avoid battery drain are reducing the number of short drives, don’t leave accessories plugged in, fixing faulty parts like the regulator and IBS unit, and replacing old batteries.
Is frequent battery drain bad for your BMW battery?
Yes, frequent battery drain is bad for your car’s battery. It can cause permanent battery damage. What’s more, it may no longer be able to fully charge the battery and the full charge may not last long. So, to prolong the lifespan of your battery and ensure it works at an optimal level, it is important to avoid draining it completely.
How do I know if my BMW car battery needs to be changed?
You should change or replace your car’s battery if the headlights are dim, unexpected power fluctuations, greater need for engine revving, and the car takes longer to start the engine.
Final thoughts
Before concluding that your BMW battery is bad when you have battery drain issues, test and find out what is causing it to drain power. There are several things that can cause your BMW battery to drain as discussed above. Nonetheless, if the battery is old, have it replaced with a new and durable battery.
