Can a Car Starter Drain the Battery?

Pinpointing the actual cause of the car battery draining can be a challenge.

It takes time and requires that one is orderly to save both time and money in getting to the root cause of a flat battery.

While it’s probably not the most common cause, a faulty car starter can also drain the car battery.

In this post, I cover the signs that can show that the car starter is the cause of battery drain, confirmatory tests you can do to confirm, and how best to fix a car starter that is draining the battery.

Related posts: What can drain a car battery with the ignition off

Can a Car Starter Drain Battery?

Yes, a car starter drains the battery. It draws power from the battery when the car is started and can also drain it after when faulty.

As the car motor starts, it draws a high current from the battery to deliver enough power to start the car engine.

You may want to read: Car starter burn out – what you should know

How a car starter can drain a car battery?

The car starter motor’s power draw during starting is so significant that it is possible to drain a car battery flat.

If you make several consecutive start attempts (without the car engine starting successfully), the battery can be drained flat.

A fault in the car starter solenoid can also drain the car battery leaving it flat.

You may want to read: 2 Easy ways to know if a car alternator is draining a car battery

Does a Starter Drain the Battery?

During the normal operation of the car, the car starter motor only drains that battery as the engine starts only and stops when the engine is running.

If the starter motor is faulty, depending on the nature of the fault, it can continue draining the battery even when the engine is switched off.

Signs that Car Starter is Draining the Battery

Pinpointing why a car battery is being drained flat can be challenging sometimes.

If your car battery is draining flat, working through the checklist organized in order of likely causes of battery drain can help you identify the causes efficiently.

#1. Check for and disconnect any electronic accessories, lights, aftermarket accessories – like a sound system that may be drawing excessive amounts of power from the battery

#2. Check and confirm that the car battery connections are clean, firm, and make good solid contact with the battery posts.

#3. Check and confirm that the battery is still in a good condition – you may need to arrange for a load test to be conducted on the battery.

#4. Confirm that the alternator is charging the battery

If the battery is still being drained flat, you can then look at the starter.

#4. To check if the car starter is responsible for the high parasitic current draw, you can conduct current draw measurements while disconnecting the starter motor supply and exciter cables in turn.

Check if there is a reduction in the current drain. If disconnecting either of the wires reduces the current drain, then it is quite likely that there is a fault with the starter.

Alternatively, you can have the car starter checked at an auto mechanic workshop.

Causes of Battery Drain by Car Starter

There are 3 main causes of battery drain by a car starter:

  • Expected high current draw of power from the battery when the car starter motor engages the engine.
  • You may also have a fault in the car starter motor solenoid that causes battery drain.
  • A stuck car starter relay or ignition switch on the starting circuit can also cause battery drain.

Fix for a Car Starter Draining Battery

Assuming the cause of battery drain was narrowed down to the car starter if the problem is with the starter solenoid, it may be possible to replace the solenoid (that matches the original) or even replace the entire starter motor assembly.

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#1. Can a Starter Cause a Parasitic Current Draw?

Yes, a faulty starter can cause a parasitic current draw, for example, a short circuit in the starter solenoid that leads to continuous and unusually high current draw that drains the battery flat.

#2. Can a Starter Drain a Battery Overnight?

Yes, a faulty starter can also cause a battery to drain overnight. Check out this post for common causes of battery drain by a starter.

Before zeroing down to the starter, it might save you both time and money by working through the checklist above of common causes of battery drain ordered in order of likelihood.

#3. Can a Remote Starter Drain a Car Battery?

Yes, a remote starter can drain a battery flat especially if the battery is not in good condition, not properly wired, poor quality starter, and the battery is parked for a long time.

A remote starter in standby mode draws a small current usually in the order of mA to keep its internal electronics alive while it awaits the remote start signal.

If you suspect that the remote start is draining the battery, consider temporarily disabling it by switching it to valet mode ( consult the user manual) or disconnecting it and checking if the excessive battery drain is caused by the remote start system.

#4. How Much Does Starting a Car Drain the Battery?

At startup, a car engine can draw anywhere from 90 – 200 A from a car battery depending on the engine size and car starter motor size (kW). The power draw is momentary and can last 5-10 seconds.

If the battery is in good condition and fully charged, this large current draw will not drain its capacity significantly.

An aging or partially charged battery on the other hand can be drained flat when these large currents are drawn from it.

Summary

A car starter can drain the car’s battery flat in several ways.

As your start the car, the car starter motor draws a high current from the battery to be able to start the engine.

In addition, a fault in the magnetic switch relay such as a short-circuit can also drain the battery’s power.

If you suspect that the car starter motor is faulty, depending on the nature of the fault, you may be able to replace the faulty solenoid or even replace the entire car motor starter assembly.

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