Electrical Battery Drain Problem

[Boiler2]

Hello,

So I am having a battery drain issue that started about 4 years ago. My car has been in storage for 3 years as I have been living in China (different story). I am in the process of moving back now. Before storage, the car would start slowly but still start and run fine. In storage, the battery would die out and need to be jump started. Went through 3 batteries in 3 years as I was not around to deal with the issue. I had someone start and run the car every other month while in storage.

So now I am back and started trying to address the issue. I of course started researching online and found a number of helpful things as I am not an electrician or anything and have a test light and multimeter. Here is what I found thus far:

- Removed the alternator and had it tested at the parts shop ... it tested fine.
- Disconnected the positive battery cable and used test light - it light up for about 10 seconds then went out. Is this normal?
- Traced it to the "room lamp" fuse in the fuse box in the engine compartment. Looked at the electrical drawings and they are a bit confusing to me. Does anyone have a list of those items powered by the "room lamp" fuse?
- Removed all fuses from the fuse box inside the car and same issue with the test light. Also checked all fuses and none were bad.
- Then tested volts from the positive battery post to the different positive cables. Pulling 11.6 volts to the fuse box and 13.7 volts to my bazooka sub in the trunk (all off). Is this normal when they are all turned off?
- Then tested amps - the cable to the fuse box had 2.8 initially, then 1.7 after 1 second then 0.3 after about 10 seconds. These were on the 200m setting on the multimeter.
- Disconnected the 12v supply to the radio and the amps were just 0.3 steady with all off on the 200m setting. Is this too much pull with all off to drain the battery? Is this 30 milli-amps?
- I have an aftermarket headunit, no stock amp, and most of my gauges are hooked into the cigarette lighter. I disconnected the ground wires and tested again with the same issue, and also cleaned the grounds for these and changed the ground for the headunit.
- I also re-checked the aftermarket headunit hook-ups per the printed wiring harness diagram and install instructions and all seems OK.
- Checked the grounds for the sub tube in the trunk.

I am thinking I need to go back to the alternator and test further. What are your thoughts? I feel like I am taking the shotgun approach to problem solving which is not really my style. Any direction would be appreciated.

Thanks!

 

[19gale2gGST]

The ALT shouldnt cause a drain by itself. You didnt say you checked yourr ground wires, or the wireing harness for shorts bald or grounding spots. Also corrosion on the wires and cables will cause a battery drain.

 

[Boiler2]

Also ... the car does hold a charge when running. At idle it reads 13.8+ volts.

 

[luv2rallye]

Pulling some current when first connecting battery for a few seconds is normal as it powers the ECU backup, radio station memory/clock, and possibly (I don't remember if this also happens at battery connection time) the rearview mirror, ignition key, and foot lights (like when a door is closed and lasts about 10 sec).

30mA is normal constant draw to power ECU backup, radio station memory/clock and should not drain your battery enough to where it won't start the car.

11.6V at fuse box and 13.7V to bazooka sub in the trunk (all off) indicates a short or excessive current draw at that fuse box. You should read the same voltage at the fusebox as right across the battery terminals (which I assume is also 13.7 - remeasure this to make sure as subs often contain very large caps which store voltage and can mislead you). If fusebox voltage is less than battery start disconnecting things on the fusebox to find source. Start with non-stock items.

13.7V at idle is a little low (normal is 14.4) but if you have a large enough short that may be pulling it down.

Sounds like you may already have found my article: http://www.dsmtuners.com/forums/art...-partial-short-battery-drain.html#post1496998

 

[twoTSis]

Be sure to double check more obvious solutions too: battery cables not connected properly or corroded, etc.

 

[Boiler2]

Thanks for the updates! I did read the tech articles and followed those to the best of my abilities. I will definately check the voltage comparisons at the battery and the fuse box. I agree that 13.7 volts while running is low. I used to get 14.4 or 14.6 but not any more. The voltage measurements I listed were between the + battery terminal and the wires which connect to the + terminal. (I had disconnected them and then measured the voltage between them)

Good call on the battery connection corrosion. I did in fact check these about 6 months ago when I was in town briefly and did change both the negative and positive terminal connectors. I did not notice much change so they must have been ok. The cable from the + battery to the fuse box is a bit old. I will try to check that as well.

- Can an alternator tested at the auto parts store test OK but actually be "dying" but acceptable by their tests?
- When I say "Disconnected the 12v supply to the radio and the amps were just 0.3 steady with all off on the 200m setting." On the 10 amp setting on the multi tester, this reading read 0.03. I am still a bit confused as to whether this is 30 milli-amps or not.

I had to leave town briefly so I will have to continue testing once back in town. Thanks for the help thus far!

 

[luv2rallye]

- Can an alternator tested at the auto parts store test OK but actually be "dying" but acceptable by their tests?

DEFINATELY and happens very often. The only place that tests alts properly is an alt/starter repair shop.

- When I say "Disconnected the 12v supply to the radio and the amps were just 0.3 steady with all off on the 200m setting." On the 10 amp setting on the multi tester, this reading read 0.03. I am still a bit confused as to whether this is 30 milli-amps or not.

On the 10A setting 0.03 would be 30mA which should be correct and accurate (+/- 0.01) since the meters internal resistance is very low on that scale.

On smaller current settings the resistance of the meter is higher and when that resistance gets significant compared to the resistance of the circuit you're measuring the current of (usually when the meter's resistance is more than 5% of the circuit's resistance), the meter "loads" down the circuit and you get an incorrect and misleading reading (eg. 0.3 on the 200mA scale which says it's 0.3mA or 300uA). The smaller the setting (or scale) the higher the meter's resistance. This resistance is placed in series with the load which will give you a lower current reading than you actually have (since you just placed more resistance in the circuit). This is why the lower scales which you would think would be more accurate actually are worse if the meter's resistance isn't way way less than the circuit's. [hint: So when you don't know the circuits resistance, which is often the case, use the higher setting - you get less digits but they are more believable and true.]

This is true for typical multi-meter current measurements. For typical multi-meter voltage measurements the higher scales have higher resistance so they load down the circuit less. But the meter still always places resistance in parallel with the load on voltage scales. So again, you will get an incorrect and misleading reading on low scales where the meter's internal resistance is significant compared to the resistance of the load (usually when meter's resistance is less than 20 times that of the load). This decreases the resistance of the circuit you're measuring (since you just placed resistance in parallel with it) and usually results in a lower voltage reading than you actually have. Oscilloscopes and very expensive meters don't have these problems anywhere near what multi-meters do but then ... they're very expensive.

Another thing to remember with all digital meters is any reading on any scale is always +/- one least significant digit. Examples: 120.5V is 120.4-120.6V.; and 5mA is 4-6mA; and 5.0mA is 4.9-5.1mA; and 5.00mA is 4.99-5.01mA; and 1 ohm is 0-2ohms; but 1.0 ohms is 0.9-1.1 ohms; and 0.99 ohms is 0.98-1.00 ohms; etc.

 

[Boiler2]

Thanks luv2rallye! This helps greatly. I will keep everyone posted on what gets to the bottom of this.

 

[Boiler2]

Well ... quick update. Got back to testing and pretty much I do not think there is a battery drain. I believe it is the alternator. With the car at idle and everything off, it reads 13.8 volts. While running with the headlights, heater, and wipers on, it drops to 12.7 volts. Based on the docs I read, this is an alternator issue.

I did have the alternator checked at the local auto shop earlier and it tested fine so let this be a lesson. I also had some weird readings on my multimeter due to a low 9v battery so another lesson learned. I plan to replace the alternator soon and will repost results. Thanks for the help.

 

[Boiler2]

Drove the car 800 miles to my new location and it made it. Gotta love it for the fact it was in storage for 3 years with minimal engine runs and then travels that far.

Voltage read 13.6 - 13.7 for the first 2 hours, then 13.4 - 13.5 most of the way except when going up large hills on the highway or when the car was under a heavier load at which point it read 13.1. Once the load was off, it went back to 13.4 - 13.5 after a few minutes. At one point, I turned the headlights on and heater and wipers and it dropped to 12.7 and I quickly turned them off. After I made it, I tested the battery voltage with the car off and no issues ... 12.7 volts.

Are these still the symptoms of a bad alternator? Can anyone confirm? Thanks.

 

[GirlDriver]

Wow, your problems sound about as complicated as mine with my '96 GS-T. But my battery would drain overnight and the alternator is good. Basically, what my husband ended up doing was putting a kind of "kill switch" on the car. When we get out, we turn the breaker off and when we get ready to drive it again, we turn the breaker back on and we are good to go. It sucks, but it works. We tried everything we can think of. I even have the electricians manual and couldn't figure it out...

Good luck with yours! At least if you drive it every day, it doesn't die on you...