Current drain

2848 Views 24 Replies 7 Participants Last post by HUF, Apr 29, 2009

HUF

Discussion Starter · Apr 9, 2009

I am still trying to figure out why my new battery gets drained... I measured the drain current with everything turned off , doors, trunk locked. The digital multimeter showed something irrelevant (2.5 mA), so I bougt analog one. Unfortunately, the range for high ampers is 20A. The current is between 1A and 500mA. I could not get a better data since the next range is 500 mA.
The alternator puts out 13.7 - 14.8 V. There are no charging system related codes or telltales. The ripple voltage of the alternator is 32mA (if one can trust that DVM). Tha indicates the diode bridge is fine. The battery passed load test.

1. What is your current drain on 4.9 gents?
2. Why are DVMs so tricky when it comes to current measurements?

Thank you in advance!

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steelybill

· #2 · Apr 10, 2009

You may be able to narrow it down by having the meter between the bat and the cable ( like you maybe already have done), and start pulling fuses and plug-in circuit breakers one at a time to see if the draw changes.

DVMs can not always do what an analog meter is good for. I would use which ever shows a draw for the test I mentioned. Hope this is of some help.

BILL

Dave S Texas

· #3 · Apr 10, 2009

Todays vehicles all have parasitic drains on them. Any electronic unit that has a memory function is draining the battery: computer/radio/audio-player/even some electronic mirrors. Cold temps also have a effect on batteries. A new battery will last much longer if it doesn't go through drain/charge cycles. Toward that end and because my car is garaged most of the time, I use a Battery-Tender. Those units will slow-charge a battery and then keep it close to 100% charged.

behind-bars

· #4 · Apr 11, 2009

I had no luck finding my drain with a meter, I put a test light between the negative terminal and cable and went to pulling fuses until the light went out. Mine was a courtesy light fuse under the glovebox. I dont remember what my drain voltage was though.

steelybill

· #5 · Apr 11, 2009

If that fuse being out made your test light go out, it was because you had a door open , right?
Doesn't sound like you really found a drain source yet.
So how long does the car set around before the battery goes down?
Like Dave S said, many low drain items are on all the time.

behind-bars

· #6 · Apr 11, 2009

steelybill said:
If that fuse being out made your test light go out, it was because you had a door open , right?
Doesn't sound like you really found a drain source yet.
So how long does the car set around before the battery goes down?
Like Dave S said, many low drain items are on all the time.

I had another thread on mine, It is all fixed now. My battery would drain overnight. I had done some work inside the door panel a few months prior and when I plugged the lights in the armrest back in one was backwards; which goofed up the circuit I guess. The lights were not working since it was plugged in wrong, but it caused a drain on the battery. Once I isolated the problem to the lights, via test light and pulling fuses, I got them plugged in correctly and the test light on the battery does not light up anymore and the battery doesn't drain to the point of not starting.

HUF have you done any sort of other work in the past few months with anything electrical in the car? My lights were plugged in wrong, unknowingly causing a drain, for over a month before the car would not start so I had initially ruled that out.

HUF

Discussion Starter · #7 · Apr 11, 2009

behind-bars said:
HUF have you done any sort of other work in the past few months with anything electrical in the car?

Nope, nothing has been done on the car recently.

Sevillian273

· #8 · Apr 19, 2009

This might be a stupid question but are you certain that you have the right size battery? I only ask because my 90 came with a battery that was one size too small (75-S) but I didnt know it. Ten minutes with the glove box open or 3 days w/o starting the car and the battery would be dead. I even had it tested and it passed fine. I went through everything before I realized it needed a bigger battery (78-S).

HUF

Discussion Starter · #9 · Apr 20, 2009

Sevillian273 said:
This might be a stupid question but are you certain that you have the right size battery? I only ask because my 90 came with a battery that was one size too small (75-S) but I didnt know it. Ten minutes with the glove box open or 3 days w/o starting the car and the battery would be dead. I even had it tested and it passed fine. I went through everything before I realized it needed a bigger battery (78-S).

Yes, it is a correct size battery.

steelybill

· #10 · Apr 21, 2009

I had a battery drain years ago, which turned out to be trunk light wiring. It was intermittent also which made it difficult to find. Sometimes it's something simple.

HUF

Discussion Starter · #11 · Apr 21, 2009

steelybill said:
I had a battery drain years ago, which turned out to be trunk light wiring. It was intermittent also which made it difficult to find. Sometimes it's something simple.

I am coming to conclusion that nothing is wrong with charging system and most likely with the battery as well. The other day I drove some 100 miles, parked the car for 5 hours, went back - battery was dead to the extent I could not jump start from another battery (I always first disconnect the donor battery from donor car just in case). Had to ask the guy to start his car to be able to start mine. Sometimes my car can sit for days without draining the battery and it can drain it in hours the other times. I think I can exclude the regulator. Can a regulator act up intermittently?

cadillac_al

· #12 · Apr 21, 2009

My 94 Park Avenue and my Caddy will both drain the battery if they sit idle for more than 7-10 days. I haven't bothered to figure out why so I just try not to let them sit that long. I almost started thinking it was normal but it probably isn't; although a battery can only power the memory/clock functions for a finite period of time. I would think it would be more than 10 days though.

HUF

Discussion Starter · #13 · Apr 21, 2009

Okay, I have measured the current drain with different multimeters including an analog and looks like it is around 600 mA. Sure it is too much, BUT I still cannot understand how can 0.6A drain a 100Ah battery in a few hours!

cadillac_al

· #14 · Apr 22, 2009

I don't either. I somehow missed that 5 hour part. That's not good. The culprit must not be drawing while you are testing. I'll bet mine is around 600ma. I'll try to test it tomorrow if I can get some time. That must be a heavy draw because a dome light or radio or trunk light won't kill a battery in 5 hours. I wonder...... if you actually stood there and watched it for 5 hours if the battery would really die with a 600ma draw. I would almost be curious enough to do it if it was mine.

HUF

Discussion Starter · #15 · Apr 22, 2009

cadillac_al said:
I don't either. I somehow missed that 5 hour part. That's not good. The culprit must not be drawing while you are testing. I'll bet mine is around 600ma. I'll try to test it tomorrow if I can get some time. That must be a heavy draw because a dome light or radio or trunk light won't kill a battery in 5 hours. I wonder...... if you actually stood there and watched it for 5 hours if the battery would really die with a 600ma draw. I would almost be curious enough to do it if it was mine.

I am coming to conclusion that nothing is wrong with charging system and most likely with the battery as well. The other day I drove some 100 miles, parked the car for 5 hours, went back - battery was dead to the extent I could not jump start from another battery (I always first disconnect the donor battery from donor car just in case). Had to ask the guy to start his car to be able to start mine. Sometimes my car can sit for days without draining the battery and it can drain it in hours the other times.
It could be also a combination of failures. Say, battery did not get enough charge during 100 miles trip because of the regulator (the voltage from alternator was 13.7 -14.5V during the trip) and was easily drained with 600mA carrent, OR at that particular day the drain was much higher than 600 mA. Mistery continues... lol

AMENCADDY

· #16 · Apr 23, 2009

To isolate the problem, pull every fuse that you can live without and see if the problem still exists. if it goes away, then start putting the fuses back until the problem recurs. That will pinpoint the offensive circuit and you can nail it down from there.

HUF

Discussion Starter · #17 · Apr 24, 2009

I hate inconclusive experiments, but that's all I have got at this point. The current drain about 450 mA with fully charged battery (12,75v) would drop to 120 mA in somewhere between 15 and 30 minutes. If I disable security system by pulling out 15A fuse the draw will be about 15 mA. I do not care about security, but with the fuse pulled out the dash would not illuminate at all... So, there is 120 mA drain after the car is locked and security system is in charge. Pulling out all other fuses did nothing. I have disconnected all the plugs in trunk just in case. By the way, a $2.99 digital multimeter from Harbor Fraight and a 12V test bulb work very well. Any noticeable current draw will turn the bulb on, and cheap multimeter handled all the tasks very well. Even if you burn it , it is still only three bucks ! lol. The dash draws about 8-9 A and when leveling compressor is engaged the draw jumps to some 15 A, so be careful. A dome light, trunk light, glove box light draw about 0.5A.
I believe 120 mA is till too much (despite I cannot see how it would drain 100Ah battery overnight). Any suggestions, gents? Thank you!

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AMENCADDY

· #18 · Apr 24, 2009

Actually, it is very conclusive, but before I can do the ohms law math, could you please answer a couple more please, Huf.

1) What is your battery Voltage reading after 30 minute intervals for the 5 hour period which you said it is dead? somewhere in there your battery takes a nose dive and you can correlate the time with the event, unless it is a steady parasitic draw.

2) what is the amp hour rating on your Bat and the cold cranking rate?

Thanks, Don't despair. progress!

HUF

Discussion Starter · #19 · Apr 24, 2009 (Edited)

AMENCADDY said:
Actually, it is very conclusive, but before I can do the ohms law math, could you please answer a couple more please, Huf.

1) What is your battery Voltage reading after 30 minute intervals for the 5 hour period which you said it is dead? somewhere in there your battery takes a nose dive and you can correlate the time with the event, unless it is a steady parasitic draw.

2) what is the amp hour rating on your Bat and the cold cranking rate?

Thanks, Don't despair. progress!

AmenCaddy,

1) I did not monitor the voltage when the battery got drained (otherwise I would not let it happen! lol). If I leave the battery alone (disconnectred from the car) , it will hold the voltage pretty good. I even load tested it some day and it passed.
2) The DieHard I had before was 900CCA and 1000CA, this NAPA one is a bit weaker, probably 800CCA and 900CA. I could never find information about the capacity in Ah. I do not understand why they never mention that important parameter.

The problem is aggravated with its intermittence. Sometimes the battery is fine after sitting for a few days CONNECTED to the car, and as I mentioned before, sometimes it got drained overnight or even in 5 hours!

AMENCADDY

· #20 · Apr 24, 2009

Ok, thanks. I'll do some more calc now but I may have to keep asking silly questions like this one, did the battery fail after you did your fuse tests/ amp readings? or is it still okay now.

To be honest, being a retired mechanic (always fix mine last or live with the problem) I have similar battery problems with my Lincoln and the Caddy, but here's how I workaround it for now. by carrying a Spare battery with jumper cables. Everytime I get hit with this intermittent gremlin, I just haul out the spare and jump start my car. Works for me!! until I can find the little b-tard thats sucking too much juice. :want:

1 - 20 of 25 Posts

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