13 TE; turn key to Acc. position and listen to radio only for 20 mins. and just about drains battery. 165,000 mi, and it has done it since day one, I change batteries before they change me. Just curious. Thanks
Acc. position drains battery 20 minutes??
Timcono
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Yup, normal. Gotta figure, in ACC mode it's running all the computers and dash screens. Pretty decent voltage draw, especially on the standard flood acid battery. Swap in an AGM and it'll be a little better. Better yet, keep the engine running, or keep a battery jump pack in the trunk....just in case.
Roughly, it sounds like your battery is getting worn out. In my experience when batteries reach their end, that means their "capacity" gets too low. Your test there is exactly what would challenge a battery with low capacity. And it's the sort of test I would do in my driveway on a doubtful battery to confirm whether it needs replacement, regardless of what my battery testers say.
Some numbers to consider ...
![Image]()
That's the battery in my 2011 LX, from Home Depot. In the upper right corner is the capacity spec: RC MINS:120
That means the "Reserve Capacity" is 120 minutes, as in two hours. So if the battery is fully charged, as it would be after driving, with a 25 Amp draw, it will take 120 minutes before the battery voltage drops below 10.5 Volts, which I guess is considered the point at which the car will probably not start. <== that is what the specification is designed to mean.
You could measure your current draw in ACC mode if you've got the right tool, but I'll suggest it might be around 20 Amps. To make the math easy (Friday afternoon, you know ...) call it 25 Amps to match the spec, and say your battery has the same 120 minutes RC MINS spec as mine does. So that means it should last two hours before getting dangerously low (when the battery is new) vs. your 20 minute result.
It could be you're drawing a lot more than 25A. Or it could be that your battery is getting toward end of life. For me, low capacity is always what ends a battery for me. If all you need to do is drive, stop, turn off, turn on, start, etc. you can have pretty low capacity and it will get it done. But sitting with the engine off drawing power will cause problems quickly.
Some numbers to consider ...
That's the battery in my 2011 LX, from Home Depot. In the upper right corner is the capacity spec: RC MINS:120
That means the "Reserve Capacity" is 120 minutes, as in two hours. So if the battery is fully charged, as it would be after driving, with a 25 Amp draw, it will take 120 minutes before the battery voltage drops below 10.5 Volts, which I guess is considered the point at which the car will probably not start. <== that is what the specification is designed to mean.
You could measure your current draw in ACC mode if you've got the right tool, but I'll suggest it might be around 20 Amps. To make the math easy (Friday afternoon, you know ...) call it 25 Amps to match the spec, and say your battery has the same 120 minutes RC MINS spec as mine does. So that means it should last two hours before getting dangerously low (when the battery is new) vs. your 20 minute result.
It could be you're drawing a lot more than 25A. Or it could be that your battery is getting toward end of life. For me, low capacity is always what ends a battery for me. If all you need to do is drive, stop, turn off, turn on, start, etc. you can have pretty low capacity and it will get it done. But sitting with the engine off drawing power will cause problems quickly.
Yes, ACC, that's why it blows my mind @ 20 mins...and since new, but I rarely use ACC so I forget between uses.
To remove some uncertainty from your situation, you could use a clamp ammeter to see just how much current you are drawing, in either ACC, ON, or off. Better info is usually key to better decisions. Here's the first item that came up on Amazon just now when I searched for DC current clamp ammeter:
Cheaper ones will offer everything except DC current, which would be useless here, so be careful on that. I'm not endorsing this one, just showing an example. I've got a few of these tools, with varying ranges and sizes (e.g., smaller or bigger clamp for different applications.
I know it's stuff to buy, but if it can save you from buying a battery / alternator / etc., it may pay for itself in one use.
Maybe there is something running on your car in ACC that is drawing a lot of current and draining a good battery too quickly. Or maybe the battery is worn out. If you end up replacing the battery, you could see how realistic the RC MINS spec is when new. As mentioned, to me, that is the most important battery variable - determines when a battery can no longer do the job.
KAIWEETS Digital Clamp Meter Multimeter with D-Shaped Jaw for AC/DC Current & Voltage, Auto-ranging 4000 Counts Voltage Tester with Flashlight Backlight, Measuring Temperature Continuity Diode NCV: Amazon.com: Industrial & Scientific
KAIWEETS Digital Clamp Meter Multimeter with D-Shaped Jaw for AC/DC Current & Voltage, Auto-ranging 4000 Counts Voltage Tester with Flashlight Backlight, Measuring Temperature Continuity Diode NCV: Amazon.com: Industrial & Scientific
www.amazon.com
Cheaper ones will offer everything except DC current, which would be useless here, so be careful on that. I'm not endorsing this one, just showing an example. I've got a few of these tools, with varying ranges and sizes (e.g., smaller or bigger clamp for different applications.
I know it's stuff to buy, but if it can save you from buying a battery / alternator / etc., it may pay for itself in one use.
Maybe there is something running on your car in ACC that is drawing a lot of current and draining a good battery too quickly. Or maybe the battery is worn out. If you end up replacing the battery, you could see how realistic the RC MINS spec is when new. As mentioned, to me, that is the most important battery variable - determines when a battery can no longer do the job.
led interior replacements but they don't draw when in ACC position.
Great info, thanks.
Sounds like it's time to replace the battery. I noticed some issues with my 2014 acting a little weird and once I left the emergency flashers on for about 15 minutes and when I came back it wouldn't start. After jumping it and putting it on the charger at home overnight I took it to the auto store they ran a test and said it tested fine but it did it again soon thereafter so I replaced the battery and no issues since. So before you start Chasing Ghosts or worrying about other more serious possibilities I would replace the battery. Frankly, they don't last like they used to.
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Killing a new battery in 20 minutes of radio use shows something substantial drawing current. I would pull the fuses for everything that turns on when the ignition switch is in the accessory position and replace them one at a time to isolate the faulty circuit. Before you do that, though, I would suggest pulling the fuse for the radio and see if the fast drain still happens. Splurging on a clamp on ammeter would significantly shorten the troubleshooting process. Just get someone to watch the meter while you sequentially pull fuses and replace them.
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