Is a .26-.27 amp draw enough to drain a battery?

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I'm seeing that a typical multimeter reading when the car is off is 50 milliamps or below. I'm seeing .26-.27 amps while testing. Is the 50 milliamp accurate and is what I'm seeing enough to be a parasitic drain on the battery?
 
Typical new car battery is about 60 amp-hours at 25amps draw. that goes up at lower current since the internal losses are less. say 80 amp-hours at .25amps. So it would take 320 hours (13 days) to discharge the battery to 10V. As the battery gets older these number come down.
 
A typical small car car battery has a Amp-hr rating of 60 amp-hrs.

For example, 60 Amp-hr./0.05A of current draw = 1200 hours of supply current and 60 Amp-hr./0.25A = 240 hours of supply current.

google your exact car battery and see what the equivalent Amp-hr rating might be.

Divide the resulting hours of supply current by 24 Hours/Day to get the ballpark number of days to discharge the battery.
 
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Originally Posted by AshleyQuick
I'm seeing that a typical multimeter reading when the car is off is 50 milliamps or below. I'm seeing .26-.27 amps while testing. Is the 50 milliamp accurate and is what I'm seeing enough to be a parasitic drain on the battery?


If I recall, 30-60 mA is normal. .26 amps is 260 mA and is 4 to 8 times more than is should be. Time to check voltage drop across the fuses with doors and hood simulated closed.
 
When are you measuring that current exactly? I went through this on my old BMW and it draws about that amount immediately when turned off but ramps down to a much lower current within a minute or so as the loads are shed.

If it's still drawing that current after a few minutes then there is definitely something wrong.
 
Any discharge greater than 50% of the total available AH's causes accelerated decline in capacity.

the shallower the cycles the longer the life of the battery

UD
 
Originally Posted by AshleyQuick
I'm seeing that a typical multimeter reading when the car is off is 50 milliamps or below. I'm seeing .26-.27 amps while testing. Is the 50 milliamp accurate and is what I'm seeing enough to be a parasitic drain on the battery?
As Atikovi has said, 0.26 A = 260 mA (and 0.27 a = 270 mA). That sounds really high. Will it drain your battery? Yes, given enough time, and much more quickly than typical "dark current" of 50 mA.

I would troubleshoot by pulling fuses one at a time until you find the culprit. (When the current suddenly drops to c. 50 mA after you've removed a fuse, you'll know that the current-hungry device is on that circuit. You'll likely need a schematic to determine what's on that circuit, but if you're lucky the circuit will be dedicated to one device.)
 
Originally Posted by AshleyQuick
I'm seeing that a typical multimeter reading when the car is off is 50 milliamps or below. I'm seeing .26-.27 amps while testing.


If you are using a DC clamp meter, be sure it is properly set to zero where it is in use. Magnetic fields in the underhood area can give spurious readings.
 
also check after the car has been off for 10min.. many cars dont shutdown completely for a few mins.. also make sure if your hood has a light or sensor you make it think the hood is closed.
 
You didn't mention the make model year of vehicle but generally the completely off state is a few tens of mA,

The thing is, the completely off state on many vehicles made in the last 25 years or so, is on a battery saver type circuit that keeps more things energized for a certain time period, during which it is typical to see a few hundred mA.

Depending on the vehicle there are events that reset the higher energy state time-out period, for example unlocking the doors, opening the doors, opening the hood if it has a switch detection, reconnecting the battery after disconnected, etc.

For this reason it is best to have the hood open, leave the battery connected for at least an hour (or research the time out period for your specific vehicle), and when you break a circuit to measure parasitic drain, you should have the multimeter in series with the circuit already so it is never truly broken to result in the higher power state (until time-out). This can be accomplished with alligator clip terminated meter jumper wires, or a second helper for more hands, or other rigged contraptions depending on where you are breaking the circuit.

One test where you do not need to do this, not-break-the-circuit is the connection to the alternator. You can just disconnect the wire at the alternator and see if any current is leaking through it, but your figures of 0.26A-0.27A are typical of just having active circuits until a time out period.

Perhaps more context of the vehicle problem would help. Is the alternator or battery very old? Have you replaced either trying to troubleshoot this? Have you had either tested?
 
Originally Posted by Rand
also check after the car has been off for 10min.. many cars dont shutdown completely for a few mins.. also make sure if your hood has a light or sensor you make it think the hood is closed.


Ditto. Last time I had to check for a parasitic load I noticed I had to wait a few minutes before the current dropped to a minimum. I believe on that car it was the lighted circle around the ignition that stayed on for a while.
 
I've seen ECUs pull a quarter of an amp on and off for about 20 minutes after shutdown. Heck, a volvo with the AC on last cycle waits about an hour then runs the cabin fan for 5 minutes or so to dry it out (if certain conditions, like battery health, are met).
 
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