1998 Outback Battery Drain when Parked

[jeffx]

I've been having problems with my battery losing its charge and not being able to start my car without a jump. I've done quite a bit of reading on the boards regarding this problem in 1998 OBW, especially where it concerns "always on" features in the various components (radio, remote locking, ecu, etc.) I've been disconnecting the battery terminal when I put the car away for the night (etc.) and this, at least, allows me to start it. I had my battery and alternator tested, but am not certain if I am interpreting the results correctly. I want to rule out the battery and alt as causes for this problem first so that I can concentrate on isolating the source of this battery drain.

 

The results of the battery/alternator test:

 

battery test

voltage: 12.94

505 CCA

500 CCA

 

Starter test

voltage: 11.60v

 

charging system

no load 14.19 v 20.3a

 

loaded 13.86v

47.8a

 

drain test 0.00a pass

[NOMAD327]

If it goes down overnight with the battery connected, and doesn't go down overnight with the battery disconnected, it's not the battery. I always suspect the alternator second after an internal short inside the battery. The charging diodes in the alternator also serve to prevent backfeeding current to ground through the field windings when the motor is turned off. I would disconnect the alternator as a test, because it's easier than trying to track each individual circuit in the car while looking for a parasitic drain. If the alternator is OK then you have to pull individual fuses and check for current loss one circuit at a time unless you can narrow it down by some other manner.

[jeffx]

Thank you. Would anyone else care to take a stab at interpreting the data from my battery/alt test?:-\

[OB99W]

Thank you. Would anyone else care to take a stab at interpreting the data from my battery/alt test?:-\

Sure.

 

[...]battery test

voltage: 12.94

505 CCA

500 CCA

Even assuming the voltage reading is with the battery completely unloaded, it's a bit high. A more typical reading would be 12.65-12.70 volts for a battery in good condition with any "surface charge" removed. It doesn't indicate a problem, but probably that recent charging (possibly just via the alternator) has left a surface charge that wasn't bled off before testing.

 

A 2.5L 4 cylinder engine with average compression and correct viscosity oil requires a battery rated at least 300 CCA (Cold Cranking Amperes) to be able to crank the engine for 30 seconds at zero degrees F without dropping the voltage below 10.5 volts (whew!). If yours has a capacity of 500 CCA or so (I don't know why you've listed two readings), that would appear to be quite adequate.

 

 

Starter test

voltage: 11.60v

I assume that's the voltage measured at the battery terminals during engine cranking. It's fine, but without knowing at what temperature, whether the engine was "cold" or already warmed, etc., it's not as revealing as possible.

 

 

charging system

no load 14.19 v 20.3a

Without knowing engine RPM, not as useful info as it could be. Assuming about 2500 RPM, voltage is about right; current is dependent on load, including whether or not the battery was just somewhat depleted by starting the engine.

 

 

loaded 13.86v

47.8a

Again, parameters missing -- what RPM, load? Your alternator apparently can output almost 50 amps while keeping the voltage above 13.8 volts, a reasonable performance.

 

 

drain test 0.00a pass

If this was a test of parasitic drain, it doesn't jive with your statement that the battery runs down when connected, but doesn't when disconnected. In fact, if the least significant digit can be trusted, it indicates that there's not even 10 milliamps of current drain. Of course, the drain could be intermittent...

[Cougar]

Looking at the results of the testing it seems to me that the battery is good. In fact, the voltage spec shown while starting seems too good to be true. I would have expected the voltage to be around 11 volts or less but that is the results I guess.

 

I have to wonder about the drain test results because it doesn't seem correct to me unless, the test was done on the main alternator lead or the starter lead. These two leads should show no current flow with the engine off but, the battery lead running to the power distribution panel which is usually around a 10 gauge wire tied to the positive post, should show some current drain normally and this is the lead that is most likely tied to the trouble spot and carries the current to all of the accessories on the car. The testing results makes me think they didn't test that area. I would have the shop that did the testing check the lead running between the battery and the power distribution panel do another current check on it. You should normally see at least a 25 milliamp draw on that wire and no more than 80 milliamps when systems go into the 'sleep' mode. If the drain is killing the battery overnight then you will see something significantly higher.

 

Hopefully they won't charge you for this additional test since they should have caught this the first time. To be fair, they may have really done the testing on the correct wire and then just compensated the results by subtracting the normal current draw. I don't know, but since you seem to be still having trouble and if the trouble isn't really due to something else wrong, I think this is what is going on.

[jeffx]

Thanks all for replies. I'm not convinced that my battery disconnect is the quick fix--but, I haven't had to jump the beast since I started doing so. A logical fallacy, probably--jumping to conclusions, definitely!

 

Advance Auto tested my car at the store after I had driven it there, so the engine was at least "warm". I'm probably a bit paranoid about it since being stranded is a drag--but it is a one-year old battery from Subaru.

 

The headgaskets failed about five months ago and I had the heads machined and replaced on a new used EJ25 (D) shortblock.

 

The electrical problems seem consistent with my experience with the older model Subarus (1981 GLF, 1984 GL Wagon, 1986 GL Wagon). Definitely a Subaru.

 

I will try to isolate the problem as suggested above.

[nipper]

Re do the drain test. you really should be showing up something even if you have a facotry radio, as it has a memory and is a drain on the circuit. The TCU and ECU have memories too. Your drain test isnt valid.

 

 

nipper

[Cougar]

The down side of disconnecting the battery for an extended time is the ECU losses its' memory. It will have to relearn the engine characteristics each time. If there is an IM test due on it there may not be enough monitors set to qualify it for testing.

 

The surest way to check the current draw on the battery is to place a ammeter in series between the negative battery post and the ground lead. An amp-clamp will work also but you need to make sure you are on the correct lead to the trouble.

[The Dude]

Actually, the downside of constantly disconnecting and reconnecting the battery is that there is a chance that the battery will expode in your face. If you're ugly, the upside is that you might require plastic surgery after the explosion. The downside is that you can't sue yourself for stupidity to pay for the surgery.

[johnceggleston]

why not pull the fuses, 2 or 3 a night untill you find the circuit? of course you'll have to have a way to jump the car in the morning until you find the culprit.

[mdjdc]

My bet is a bad alternator. The internal diodes have gone and are allowing the battery to drain. I've had the same problem and upon replacing the alternator it went away.

 

Good luck.

[nipper]

My bet is a bad alternator. The internal diodes have gone and are allowing the battery to drain. I've had the same problem and upon replacing the alternator it went away.

 

Good luck.

 

And thats easy, just unplug it over night and see what happens.

 

nipper

[aircraft engineer]

Disconnect the alternator main and field connections and do a resistance test from the output post of the alternator to ground, reverse the leads and do it again. BOTH directions should read "open circuit"

 

The "other" way to verify that it's the alternator is to disconnect the battery, pull the radio fuse (assuming the radio is the only power draw with the IGN "off"), and put a circuit tester in series from the battery terminal to the post.

 

IF it lights up, you have a "closed" circuit path with the engine off. If it shows "no circuit" (meaning the light stays "out" - that would rule out the alternator). Now if it comes "on", you COULD pull all the fuses and see if it still shows "complete circuit". (all you are doing is to put a bulb across the battery system - if there is current, the bulb will light)

 

Alternately, an amp gage in series and see what the current draw is (engine always OFF for all of these - IF you run the engine with the battery disconnected, you WILL blow the output diodes NOT "MAY" - "WILL" because the battery supplies the stabilization voltage to the voltage regulator to prevent an alternator "runaway")

 

For that kind of draw down you would need to be seeing maybe a 10 max amp draw (which would overload a lot of small VOMs)

 

I know that on one of my "other"' vehicles, I've left the dome light on overnight and it didn't matter. IF you are dropping enough current thru somewhere to draw down the battery to where it won't start, it's a SIGNIFICANT drain.

 

Maybe pull the fuses FIRST, check it and then reinstall fuses until the it "lights up". Since I don't have a circuit map, I can't tell you what IS and IS NOT connected with the key "off". Usually the radio connection is low amperage and only runs the CLOCK so it's likely not to be that much of a drain.

[jeffx]

Disconnect the alternator main and field connections and do a resistance test from the output post of the alternator to ground, reverse the leads and do it again. BOTH directions should read "open circuit"

 

The "other" way to verify that it's the alternator is to disconnect the battery, pull the radio fuse (assuming the radio is the only power draw with the IGN "off"), and put a circuit tester in series from the battery terminal to the post.

 

IF it lights up, you have a "closed" circuit path with the engine off. If it shows "no circuit" (meaning the light stays "out" - that would rule out the alternator). Now if it comes "on", you COULD pull all the fuses and see if it still shows "complete circuit". (all you are doing is to put a bulb across the battery system - if there is current, the bulb will light)

 

Alternately, an amp gage in series and see what the current draw is (engine always OFF for all of these - IF you run the engine with the battery disconnected, you WILL blow the output diodes NOT "MAY" - "WILL" because the battery supplies the stabilization voltage to the voltage regulator to prevent an alternator "runaway")

 

For that kind of draw down you would need to be seeing maybe a 10 max amp draw (which would overload a lot of small VOMs)

 

I know that on one of my "other"' vehicles, I've left the dome light on overnight and it didn't matter. IF you are dropping enough current thru somewhere to draw down the battery to where it won't start, it's a SIGNIFICANT drain.

 

Maybe pull the fuses FIRST, check it and then reinstall fuses until the it "lights up". Since I don't have a circuit map, I can't tell you what IS and IS NOT connected with the key "off". Usually the radio connection is low amperage and only runs the CLOCK so it's likely not to be that much of a drain.

 

I love teh USMB.

 

In retrospect, the previous owners had the Alternator recall service done with a Subaru rebuilt alt. However, it was done in 2001. I'm going to follow sage board advice with an eye toward a wonky alternator.

[Cougar]

The problem could be with the alternator but I am betting the problem is connected to the lead that feeds the main power panel. The simplest way to find the trouble source is to place a ammeter in series with one of the battery leads and then start disconnecting things, like the fuses one at a time, to see which one makes the current drop.

[RallyKeith]

How much is considered to be an acceptable draw when the car is off? I have a 96 that kills a battery if the car sits for two weeks. I've done the ammeter in series and only get about 40mA when the car is off. I haven't tried disconnecting the alternator yet.

[OB99W]

How much is considered to be an acceptable draw when the car is off?

Low tens of milliamps is common.

 

 

I have a 96 that kills a battery if the car sits for two weeks. I've done the ammeter in series and only get about 40mA when the car is off. I haven't tried disconnecting the alternator yet.

Let's do the math. 24 hours/day times 14 days yields 336 hours. At .04A (40mA) discharge (not an unreasonable parasitic draw), that would deplete a bit less than 13.5 A-hours. While that's not insignificant, a typical small car battery's capacity is about 45-50 Ah, so at 40mA you shouldn't be depleting more than about 1/4 to 1/3 of it. That should certainly leave enough to start the car (unless it's very cold, when thickened oil, lowered output from the battery due to temperature, etc., might make the difference).

 

I suspect the battery isn't up to par, or the parasitic load is sometimes more than 40mA.

[Cougar]

How much is considered to be an acceptable draw when the car is off? I have a 96 that kills a battery if the car sits for two weeks. I've done the ammeter in series and only get about 40mA when the car is off. I haven't tried disconnecting the alternator yet.

 

I agree with OB99W. The battery may be weak due to age or it may not be getting a full charge from the alternator due to a problem with it. I recommend you get the system load tested at a shop and and see what they say about it.

[RallyKeith]

I agree with OB99W. The battery may be weak due to age or it may not be getting a full charge from the alternator due to a problem with it. I recommend you get the system load tested at a shop and and see what they say about it.

 

Sorry to tell you guys this, but I've killed 4 (yes 4) Brand new Gold Series Batteries from Advance in the past two years. Thank god for the 3 year free replacement. So anyhow, it's not the battery in anyway. I'm thinking there may be something else going on that is intermittent and I didn't see it in the 2 minutes I was testing. I have a multimeter that logs that I plan to setup over night sometime.

 

Keith

[Cougar]

I wasn't saying the batteries were bad, though they can be damaged if things are not working as they should be with the alternator. I meant that if the alternator isn't charging the battery as it should then the battery can't provide the amount of stored power it would normally have.

 

Since you have gone through so many batteries in a relatively short period it is pretty obvious that something is not right with the charging system. I suspect the alternator has some bad diodes in it. Set your meter to measure AC voltage and place your meter probes across the battery posts. Check to see if there is any AC voltage getting to the battery while the engine is running at around 2,500 RPM, check the DC voltage also. You should have less than .1 volt AC and around 14.5 volts DC going to the battery. If you measure more than .1 volt AC you need to replace the alternator. You may also want to get a load test done on the alternator to see if it can handle a high current load.

[OB99W]

Sorry to tell you guys this, but I've killed 4 (yes 4) Brand new Gold Series Batteries from Advance in the past two years. Thank god for the 3 year free replacement. So anyhow, it's not the battery in anyway. I'm thinking there may be something else going on that is intermittent and I didn't see it in the 2 minutes I was testing. I have a multimeter that logs that I plan to setup over night sometime.

The math doesn't lie. Drawing 40mA over a two week period shouldn't drain a properly sized and charged battery to the point of not being able to start the engine. As I said, either the battery isn't up to the task (for whatever reason), or the current draw is more than 40mA. Neither I nor Cougar said the battery was the initial problem, but it could become the victim.

 

The fact that you're killing batteries in six months on average says that either they're not up to the job, or something is stressing the heck out of them. For now, I'll assume the batteries themselves aren't that bad. So, as Cougar said, there could be a problem with the alternator. Checking for too much ripple (AC) is a start. I'd also verify that the charging voltage doesn't get too high -- you can "cook" a battery. Also, if a car battery is run down too far (by leaving on accessories while parked, for example) before recharging (especially if left in that condition for some time), it will "sulfate", significantly lowering the charge capacity.

 

A battery that discharges over time doesn't necessarily have to do that via an external load. Batteries normally slowly self-discharge, but that can be sped up dramatically by conductive "sludge" at the bottom of the cells. The sludge is material that gets knocked out of the battery plates; that's doubly bad -- besides causing an internal discharge path, it lowers the amount of active material. That sort of thing can happen when the battery is subject to excessive vibration. In other words, not properly clamping down a battery can cause the problem.

 

High temperature is also a battery killer, even if not caused by the charging voltage being beyond what it should be. If for some reason the underhood area that the battery is mounted gets too warm, that can be enough for problems.

 

By the way, I typically get about a dozen years from batteries in my own vehicles. They're not "no/low maintenance" or "high performance" types, since I've found that both of those usually have shorter lives. If you keep the electrolyte at the correct level (which is one reason I like individual cell caps), don't over/undercharge, don't overly discharge, keep properly mounted, don't overheat (don't live in the deep South ), etc., you should be able to get at least 6-7 years on average.

[srs_49]

I had a similar problem with a '74 Datsun 260-Z. It had an ammeter as part of the instrument cluster and, when the car was off, it was showing a bit of a discharge. One of the diodes in the alternator was shorted, which was allowing the battery to drain. The other diodes (it was a 6 diode, 3-phase circuit, if I remember correctly) were OK and would charge up the battery once the engine started.

[jeffx]

Bump to update that I fixed the problem by tracking down all the grounding points on the chassis that I could access and cleaning and tightening them (and spraying on a bit of WD), and also cleaning and re-tightening the battery leads. Thanks for all suggestions!