Battery drains over time

toyota
corolla

#1

I have a 1994 Toyota Corolla that the battery keeps draining until dead. It runs good but if you let it set for 2 weeks the battery will be dead.
I did the short test and there is definitely a drain to ground. I removed the fuses one at a time while watching the volt meter to no result. None of the fuses I removed stopped the short to ground. I don’t see any bare or pinched wires.
Can anyone suggest something to try? I am at a total loss that to do next.


#2

Is the top of your battery dirty and how old is your battery? Also, how much is the car driven?


#3

Try, one-by-one, removing the wires to the alternator and the starter.


#4

Good ideas above.

It could also be the battery itself, with a partial short internally. You can check this by removing the connection to the + terminal and checking the voltage.

You need an ammeter, not a voltmeter to measure current. Assuming that, what current did you measure?


#5

That’s a good idea but I had the battery checked at Advance Auto.


#6

Oldtimer, the battery is relitively clean. I just ran the car to charge the battery. I put a meter between the ground terminal on the battery and the ground connection to the automobile and it show it draining,


#7

Confusing…I assume you removed the negative clamp from the battery, and measured amps between the battery negative post and the disconnected clamp, right? What were the amps you read?


#8

Yes the clamp disconnected, Between the battery post and the clamp measures 6.55ma


#9

That is well below what would be considered a problem. All hooked up and with the engine idling, what battery voltage do you read.


#10

No offense intended, but are you quite sure you read it correctly?

6.55 milliamps is neglible, and well within normal parameters

Moving on . . . do you have any aftermarket electronic equipment, such as an alarm?

As for that battery, how old is it?

An aged and/or bad battery might just not be able to hold a charge sufficiently

What I’m getting at . . . if you did indeed perform the parasitic draw test correctly and reported the draw correctly, that’s not your problem. It’s something else


#11

db4690
The battery is practically new. This has been ongoing for a while. Can you outline the procedure for the parasitic draw test? I was under the impression that there should be no draw when everything is turned off. The low draw is why it takes a few weeks to draw down in my mind anyway.
oldtimer
The voltage is about 14 when the battery is connected and engine running.


#12

They don’t check for internal leakage, as far as I know.


#13

On modern cars, there is always some draw. The computes all go into sleep mode, after some time, so your initial measurement may be high, you have to wait an hour or so.

Usually the drain is less than 50 mA. A typical car battery has a capacity of about 70 amp hours.

70 amp-hour / 0.05 amps = 1400 hours or 58 days. So at 50 ma, a typical battery will last almost 2 months.

Are you sure that’s not 6.55 amps? 6.55 mA is very low. If the electronics has not had time to go to sleep, I’d say much too low.


#14

I got the reading on the 20ma scale of the meter.


#15

I actually disconnected the alternator but not the starter.


#16

Have you tried just disconnecting the battery negative terminal for your two-week down-time? This will test the “self-draining battery” theory.


#17

insightful
I will definitely try that. I am leaving town for awhile that will work perfectly.

Everyone: Thanks for all the good advice. I will try to remember to return with the results if the 2 week test. The battery in my brain drains too. LOL


#18

I had a similar problem with a Dodge Durango. Took me a while to figure out that I had an electronic air freshner plugged in that was draining the battery over days not running the car.


#19

Well I think I found the problem. I came back and connected the battery. It started immediately. I checked the battery drain again finding the drain increased to 4+A. I just by accident went to the back of the car and the brake lights were on. I checked the brake light switch. When I touched it a piece of Bakelite fell off. I disconnected the brake switch and the battery draw disappeared. After adjusting the switch everything looks and works fine. My best guess is the switch was partially closed to where the current was jumping the contacts. Time will tell.
Thanks everyone for the help.


#20

Good work - and thanks for letting us know what you found.