New battery drained overnight

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Swift101

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Hey Everyone,

On Christmas day I awoke to Sonata not wanting to start. I noticed something was wrong when I went to unlock my car and the horn didn't chirp. Eventually I got into the car and had the battery load tested, it showed 4 volts. I jumped the car and haven't had a problem since, everything seems to be fine now. The battery is 30 days old, it's a autocraft silver battery which I believe is made by Johnson Controls.

I did a parasitic draw test, at first the car was using around 1.6 amps, but fell to around 170 milliamps after 2 minutes. It was still falling when I disconnected the multi-meter. I know the magic number is 50 milliamps but I know some systems take a while to shut down. I'll do a longer test this weekend to see how far it goes down. Either way I don't see how a draw of 170 milliamps could have discharged my battery in 14 hours.

One thing I did notice is I had a bunch of papers in my glove box and it's possible they got in the way of the connector that controls the light. But could a bulb discharge the battery so much? The night before I drove for 45 minutes at highway speeds before turning off the car. But during the last mile I driving under WOT a few times which created more heat under the hood.

I do have an aftermarket alarm system but it hasn't been an issue with it since it's been installed. Also the draw test confirmed it's not using a ton of power. Any ideas? I also tested the alternator and it's working just fine.

-Thanks
 
It's quite possible that there is a high impedance short in the new battery.

My first test would be of the alternator, in case a diode went bad.
 
It is certainly possible for a single incandescent bulb to kill a battery overnight.
 
Last edited:
My mom leaves the map lights on the rear view mirror on on her Buick all the time, never a dead battery.

Take the battery to get tested, maybe it's just a bad battery. Otherwise take it into the dealer for the warranty work to find it.
 
Have you fully charged the battery after it went bad. Jumping it and driving a bit will not charge it much unless you go on a long trip during the day.

Have the battery tested. Along with charging system.

I would bet bad battery.
 
Originally Posted By: Nick1994
My mom leaves the map lights on the rear view mirror on on her Buick all the time, never a dead battery.

...


Maybe her map lights are LED?
 
a single incandescent can run all night and the car still start.

7 watt bulb. W=VI... so amps is 7/12. Call it .5 amps.

12 hours x .5 amps = 6 AH loss. A smaller battery may be 35AH capacity, a larger 70 AH.

6AH from a 35AH battery is under 20% discharge. battery can handle this.

Now, two 30W brake lamps... that's a different animal. Or, a newer car with 6 interior lamps.... that's different also. My truck has 4 dome lamps, 4 door lamps, and two tiny footwell lamps. It only runs the doors that are open, but let's say one is left open--- 7Wx5 is 35Watts.... which is about 3amps total. That, over 12 hours, will zero out a smaller battery and put a serious hurt on a mid-sized battery.
 
Originally Posted By: meep
a single incandescent can run all night and the car still start.

7 watt bulb. W=VI... so amps is 7/12. Call it .5 amps.

12 hours x .5 amps = 6 AH loss. A smaller battery may be 35AH capacity, a larger 70 AH.

6AH from a 35AH battery is under 20% discharge. battery can handle this.

Now, two 30W brake lamps... that's a different animal. Or, a newer car with 6 interior lamps.... that's different also. My truck has 4 dome lamps, 4 door lamps, and two tiny footwell lamps. It only runs the doors that are open, but let's say one is left open--- 7Wx5 is 35Watts.... which is about 3amps total. That, over 12 hours, will zero out a smaller battery and put a serious hurt on a mid-sized battery.


Well your math seems right, but I've seen it happen....and I've seen one start, so there must be some variables involved.
 
Just a quick update, I think I found what caused the battery to drain. Last night I ran to my car to plug in my phone charger and accidentally left the car in ignition on mode since I was testing to see if it worked.

Since I have a push button start setup I have to press the start button twice which enables ignition on. Normally the stock alarm system wouldn't allow me to lock the car in this mode but the aftermarket system locks the car and leaves the dashboard lit up along with the radio buttons!

It's something I'm going to have to be careful about going forward for sure. Now do you guys think I did any damage to my battery by draining it down once?

-Thanks
 
If you have an aftermarket alarm system, I would suggest that you remove it entirely and return the vehicle back to stock as much as possible.
 
Originally Posted By: Merkava_4
If you have an aftermarket alarm system, I would suggest that you remove it entirely and return the vehicle back to stock as much as possible.


I got it installed because the factory alarm is pretty quiet and lacks a shock sensor, however I can disable it if I want to. It's a Audiovox AS9234, it's tied in with a EVO-ALL bypass module (to allow remote start) made by Fortin. I have both the siren and horn hooked up to the alarm, it wakes the dead when it's triggered.
 
Originally Posted By: Swift101
Just a quick update, I think I found what caused the battery to drain. Last night I ran to my car to plug in my phone charger and accidentally left the car in ignition on mode since I was testing to see if it worked.

Since I have a push button start setup I have to press the start button twice which enables ignition on. Normally the stock alarm system wouldn't allow me to lock the car in this mode but the aftermarket system locks the car and leaves the dashboard lit up along with the radio buttons!

It's something I'm going to have to be careful about going forward for sure. Now do you guys think I did any damage to my battery by draining it down once?

-Thanks


OK, so you you're NOT saying you make a habit of leaving your car electrically ON (engine off) to charge your phone for extended periods, right? You simply did this to see how the car behaved, right?

If so, then how can you be certain this is what happened before? Do you now recall that the you killed the battery by this or are you making an assumption based on what you just did?

//

You ask whether this did any damage to you battery, but, so far as I can tell, you still haven't answered whether you charged your battery. Discharging a starter battery is not good for it, there's no getting around that; however, not a single person on this board can answer your question as to the severity of the impact.

If you are driving around with a partially or mostly depleted battery, then yes, you are currently shortening the life of your battery, and it will most certainly not last as long as it might have.
 
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