Asked by: Tiny Schutzel
automotive road side assistance

How many milliamps should a car draw when off?

Last Updated: 3rd May, 2020

11
Most vehicles draw some battery current whenthekey is off, thanks to the clock and the internal memoryofengine computers, body-control modules, and radiopresets.Altogether, they draw a very small amount ofcurrent. Fiftymilliamps would be a safe upper limit forthis, thoughmany vehicles will drawless.

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Likewise, people ask, how many amps is considered a parasitic draw?

After sitting for a few hours, the parasiticdrawcame down to 20 milliamps (.020) amps.

One may also ask, what is the average amperage of a car battery? An average car battery has a capacity of around48amp hours which means that, fully charged, it delivers 1 amp for48hours, 2 amps for 24 hours, 8 amps for 6 hours andsoon.

Regarding this, what is an acceptable battery draw?

In fact, we suggest a 25-milliamp draw isnormaland anything that exceeds 100-milliamps indicates anelectricalissue that needs to be addressed.

What can drain a car battery when the car is off?

The most common causes of parasitic drainareunder hood lights, trunk lights, headlights or glove boxlightsthat do not turn off when the door is closed.Relayswitches that are stuck in the “on” positioncanalso cause a battery to drain. Alternatorswith baddiodes can cause battery drain.

Related Question Answers

Cyrstal Arguiñena

Professional

How many milliamps will drain a car battery?

Once you have determined that the currentdrainyou're reading is safe, gradually reduce the meter'sscale to theappropriate low range, probably 2 amps or 200mA. You arenow reading the parasitic drain on thebattery. Somevehicles will show as little as 10mA residualdrain.

Olin Orengo

Professional

Can a blown fuse drain car battery?

The fuse in and of itself cannot be the causeofthe power drain. It is, however, an indication of wherethepower drain is coming from. If by pulling thefuseyou get a noticeable drop in battery drain,whatever iscausing the drain is on that circuit. Itwill helpyou narrow down what exactly is goingon.

Nouraddin Tsiulev

Professional

What is parasitic draw?

Parasitic draw or drain is a term foranelectrical component consuming electricity when it should not,evenafter it and the vehicle has been shut off. This will causethevehicle's electrical system to function improperly and thevehiclemay exhibit one or more of the following symptoms: Apersistentlydead battery.

Eloino Caneleiro

Explainer

What is a parasitic load on a battery?

A parasitic load is an electrical drainfrombattery when ignition is off.

Katy Isaichenkov

Explainer

How long will a battery last with a 1 Amp draw?

Longer answer:
In 1 hour = 0.52083Wh lost, as you multiplybyone. Therefore, in 9.6 hours, it means 5 watts is lost.Practicallyspeaking, about 4 - 5 hours. Your battery energycapacity is12 volts x 40 amp-hours, for a total of480watt-hours.

Oskia Poggensee

Explainer

What causes parasitic battery drain?

A parasitic battery drain is when an abnormalandcontinuous discharge of power occurs after having shut offtheengine. Usually, this is caused by a short circuit oranelectrical device that remains in the "on" position orenergized,such as: A trunk. An under-hood or aglove-compartmentlight.

Teressa Jantsch

Pundit

How do I test a relay with a multimeter?

Test the de-energized condition oftherelay contacts.
Use a digital multimeter (DMM) to testtheresistance between each pole of the relay andthecorresponding NC and NO contacts for that pole. All NCcontactsshould read 0 ohms to the correspondingpole.

Guasimara Yrazuzta

Pundit

Can a car stereo drain your battery?

Installed correctly, they draw a small amountofpower and won't drain your battery. Installedincorrectly,they can suck the power right out ofyourbattery. If you have an aftermarket car alarm, thenthisis one of the first things to check when you haveadraining car battery.

Sofiia Marsky

Pundit

Why does my car battery keep dying?

Some of the most common reasons for a carbatteryto die repeatedly include loose or corrodedbatteryconnections, persistent electrical drains, chargingproblems,constantly demanding more power than the alternator canprovide,and even extreme weather.

Verginiya Isasondo

Pundit

How long can a car battery sit unused?

Take a look at what the safe sitting time foravehicle is. BMW says Four weeks is the max forstoragewithout removing the battery or putting it on someform oflife support or a battery tender. The battery,ifremoved is good for about six weeks to 6 months.

Mariya Zodlvetz

Pundit

How do you check for a draw?

Pull the negative off the battery. Put thetestlight between the post and the ground wire. If thelightilluminates, you have a draw. Use the fuse pull methodtofind the draw; when the light goes out, you foundthedraw.

Judson Pudgarsk

Teacher

How do you load test a battery?

Load Test the Battery
  1. With a battery load tester, apply a load equal to one-halfofthe CCA rating of the battery for 15 seconds.
  2. With a battery load tester, apply a load equal to one-halfthevehicle's CCA specification for 15 seconds.
  3. Disable the ignition and turn the engine over for 15secondswith the starter motor.

Nafi Finko

Teacher

What causes a car to lose all electrical power?

Reasons For a Car to SuddenlyLoseElectrical Power
The vehicle won't start at all, orwillcrank slowly. Driving a car with a dead battery canalsodamage the alternator. Provide a failsafe if something drawstoomuch current. A bad starter, solenoid, or relay won'tcausea loss of electricalpower.

Martijn Baulenas

Teacher

How many amps do headlights draw?

I seem to remember that headlamps were rated at55watts, divided by 12 volts equals 4 1/2 amps per light.Idon't remember if that was high or low beam. So figure10amps for headlights and add up the rest ofcurrentdraw (I=P/V) items to see what youhave left over froma 55amp alternator.

Aleixo Nutrihin

Reviewer

How do I test my alternator?

To check an alternator, pop your vehicle'shoodand hook up a voltmeter to the car's battery by connecting theredlead to the positive terminal and the black lead to thenegativeterminal. Make sure the voltmeter reads at least 12.2volts, thenstart your car and rev the engine to 2,000RPM.

Yohandra Lecumberri-Lecumberri

Reviewer

How do you keep a car battery from dying when not in use?

Here are five ways to give your battery the TLC itneedsthis summer:
  1. Keep it cool. Since heat drains a car's battery, parking it inacool or shaded spot can buy your battery extra time.
  2. Increase your driving time.
  3. Cut down on car battery drain.
  4. Keep it clean.
  5. Get a car battery charger.

Manjinder Champion

Reviewer

How many amps do I need to charge a 12 volt battery?

A 12 volt / 10 amp 3-stageautomaticcharger is the best charger for most automotivebatteries.Unfortunately most chargers do not outputthe entire 10amps during the charge cycle, becauseitautomatically limits the voltage and theamperageduring the charge cycle.

Jeffry Villodres

Reviewer

How many amps should a 12 volt car battery have?

A typical car battery with 12 voltsratinghas a capacity of 48 Ah. It means that when fullycharged,the battery can deliver one amp for 48 hours,twoamps for 24 hours and so on.

Aylin Schweihs

Supporter

Is 300 amps enough to start a car?

You can simply jump start your car byusingbooster cables to connect the dead battery to a live one.Jumpstarters have different amp settings. Some of themrange from300 to 3,000 amps although most models forconsumersare between 400-600 amps. Most often, that isenoughfor most people's cars.

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EveryThingWhat Staff Editor

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3rd May, 2020

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