Varun916 Posted December 30, 2014 Share Posted December 30, 2014 Hi everyone, New here & did a search but didn't see anything relevant. I have a few-months old 2015 Forester that I'm loving so far. I've recently had some problems with the battery however. A few days ago the battery died completely while the car was sitting in my garage(had not been driven for ~3 days, but regular 15 min daily drives before that). The anti-theft, ignition, everything was completely dead. I used my backup-up battery to charge the battery a bit & was able to get the ignition lights on, but it didn't have enough juice to start the car. I blame the backup for that. Anyway I had roadside assistance jump the car & I drove it around for 20 minutes. Turned it off & was able to restart no problem. 24 hrs later, I try to turn it on again & the battery is dead once more. Ignition lights turn on, but not enough juice to turn over the cylinders. So I had the car jumped & taken to my local Subaru dealer, who claims they did a full diagnostic & see nothing wrong. They said the battery voltage is fine too. However there's clearly a problem here, I suspect a short somewhere that's draining the battery. Does anyone have any advice on where I can start ohm'ing out connections to see what's wrong? I'm an electrical engineer, so I feel like I can diagnose this on my own. Thanks for the help! --Varun Link to comment Share on other sites More sharing options...
lmdew Posted December 30, 2014 Share Posted December 30, 2014 Short drives, will kill the battery, as it never fully charges. High draw when you start and then a short drive never charges the battery fully. Check the voltage when running to make sure it's charging properly. Link to comment Share on other sites More sharing options...
Varun916 Posted December 30, 2014 Author Share Posted December 30, 2014 (edited) That's true, but I've driven many other cars for shorter daily drive distances without issue. Also, I'd expect a progressive drop in battery voltage & progressively harder starts. It really went from no problem starting to completely dead such that interior lights won't turn on anymore. I'll be testing the charge, as well as current for any parasitic drain. My suspicion is that the battery is probably ok, but something might have shifted causing a short. Edited December 30, 2014 by Varun916 Link to comment Share on other sites More sharing options...
keith3267 Posted December 30, 2014 Share Posted December 30, 2014 (edited) Lift one of your terminals and put an ammeter between the battery terminal and the cable to check for parasitic drain. An alternative is to lift the neg terminal and then touch the cable to the battery terminal very lightly and see if there is a spark. There should be a very small spark, if its a big one, then there is an issue. If there is a big parasitic drain, it could be a light in an enclosed space, like the glove box, vanity mirrors or trunk. I suspect that you will not get a very large spark. I think that in the end, it will turn out to be the battery. Even a new battery can fail early. They can develop an internal short, which is what I think you will find. One way to test is to disconnect the battery for a day or two and if it is dead, then you have the solution. Caution, some cars do not tolerate going without a battery for very long, these modern electronics are very sensitive. You might want to put a spare battery in or get one of those keep alive things you plug into the cigarette lighter that uses a 9V battery. Edit: a small internal short may not affect a load test on a fully charged battery so that is why the dealer missed it. Edited December 30, 2014 by keith3267 Link to comment Share on other sites More sharing options...
Varun916 Posted December 30, 2014 Author Share Posted December 30, 2014 Thanks for the advice! I'm heading over to the dealership now, will ask them if they tested the battery after charging it & will do those tests tonight. Link to comment Share on other sites More sharing options...
mikaleda Posted December 30, 2014 Share Posted December 30, 2014 I would have the battery and the charging system tested before blaming parasitic drain. Also jumping your car and using your alternator to charge the battery is extremely hard on the alternator, it's best to get it home then put the battery on an actual battery charger. Now if the battery and charging system test good, then I would lean twords a parasitic drain and have it diagnosed. Link to comment Share on other sites More sharing options...
mikaleda Posted December 30, 2014 Share Posted December 30, 2014 Lift one of your terminals and put an ammeter between the battery terminal and the cable to check for parasitic drain. An alternative is to lift the neg terminal and then touch the cable to the battery terminal very lightly and see if there is a spark. There should be a very small spark, if its a big one, then there is an issue. This is not a vaild test for a compiterized car, parsitic drain needs more time and presicion to diagnose properly, best to have a profesional do it Link to comment Share on other sites More sharing options...
mikaleda Posted December 30, 2014 Share Posted December 30, 2014 (edited) Or get one of those keep alive things you plug into the cigarette lighter that uses a 9V battery. it. This is not a good idea on a car with airbags, the backfeed in the power system could cause the airbags to deploy In certain models. When I went through training on electrical systems we were told to never use these devices for safety reasons Edited December 30, 2014 by mikaleda Link to comment Share on other sites More sharing options...
Fairtax4me Posted December 30, 2014 Share Posted December 30, 2014 The battery could have a bad or dead cell. It may show proper voltage after jumping or after a short charge but bad cell can drain the other cells after sitting overnight. I would ask the dealer to keep it for a night and test in the morning. Parasitic draw testing isn't as easy as it used to be. The control modules in the car may need up to an hour, possibly longer, to go into "sleep" mode and power themselves down. Reconnecting the battery turns all of the modules on, and some will turn on lights or actuate solenoids or some other function. The immediate current draw of all the modules combined can be enough to blow the fuse in most ammeters. To get around this you unhook the negative. Strop back several inches of insulation from each end of a fairly large guage wire. Wrap one end around the battery post (tie it if you can so its stays tight) wrap the other end around the cable terminal. Put the terminal back on the battery post. Turn the ignition on for about 15 seconds so the modules will self test, then turn the key off and remove it from the ignition. Now you can remove the negative cable from the battery, being careful not to break the connection of the wire. Connect your ammeter between the battery and cable, then after the ammeter is connected remove the wire from the cable. Doing this keeps the modules energized while you're hooking up the ammeter so they don't go into self test mode and blow your meter. This also decreases the time you have to wait for the modules to go to sleep mode. Once the battery is disconnected and reconnected, some control modules will not go into sleep mode at all until the key is cycled. They will continue to draw a high amount of current until the key is cycled. After the meter is connected wait about an hour for all of the modules to power down. If you keep close watch on the meter you may notice the drops in current as the various control modules power down and go to "sleep". Usually this should only take 10-15 minutes, but some modules can take up to an hour. GM has some control modules that can take up to 3 hours. 1 Link to comment Share on other sites More sharing options...
Fairtax4me Posted December 30, 2014 Share Posted December 30, 2014 This is not a good idea on a car with airbags, the backfeed in the power system could cause the airbags to deploy In certain models. The airbag system is isolated (or is supposed to be isolated) in such a way that stray currents or back feeds in the main power system do not affect the inflator circuitry, and can not set off the inflator modules. Something is very wrong if you plug in a memory saver and the airbags go off. Link to comment Share on other sites More sharing options...
mikaleda Posted December 30, 2014 Share Posted December 30, 2014 The airbag system is isolated (or is supposed to be isolated) in such a way that stray currents or back feeds in the main power system do not affect the inflator circuitry, and can not set off the inflator modules. Something is very wrong if you plug in a memory saver and the airbags go off. In certain older models of cars (especially dodge) the air bag system is sensitive to backfeed in the system. Its just better to use a better method than these products for safety reasons Link to comment Share on other sites More sharing options...
Varun916 Posted December 30, 2014 Author Share Posted December 30, 2014 Thanks for the input everyone. Looks like the dealer first charged the battery, then ran all their tests so as expected, internal battery problems would have gone undetected. I disconnected the negative of the battery last night & put the voltmeter in series - I initially got ~100 mA of draw for the first few minutes, but this settled to ~3 mA & stayed there. I guess the time-until-idle isn't that long on the forester. At this point, I'm not really suspecting parasitic draw from the car. With the engine on, the battery voltage was over 13 V, so it does look like it's getting charged. After running the car last night, battery was at 12.78. Checking it this morning it was at 12.57. Since 12.6 is the actual max, I think this drop is probably ok. I want to leave it another night & see how much more it drops. Will post updates. Thanks again! --Varun Link to comment Share on other sites More sharing options...
Rooster2 Posted December 30, 2014 Share Posted December 30, 2014 Suggest you get a second opinion............if you take your car to an auto parts chain store like Autozone or Advance auto, you can ask a counter guy to bring his test gear out to the parking lot. There, he will check out the charging system, and advise results of how well the alternator is charging, and if the battery is good or not. This service is done at NO cost. The idea being you will buy something to fix the problem, though there is no pressure to buy anything at all. As new as your car is, I would be surprised if there would be a short, that would be drawing down the charge on your battery I wouldn't be surprised if there is something wrong with either the battery or alternator. Even almost new batteries and alternators can fail. 1 Link to comment Share on other sites More sharing options...
Varun916 Posted December 30, 2014 Author Share Posted December 30, 2014 Thanks Rooster. I think I'll get that done tonight. Link to comment Share on other sites More sharing options...
keith3267 Posted December 31, 2014 Share Posted December 31, 2014 In certain older models of cars (especially dodge) the air bag system is sensitive to backfeed in the system. Its just better to use a better method than these products for safety reasons I don't know about older Dodges, I'll take your word for it, but newer Fords need to have a maintainer plugged in or the vehicle has to be towed to the dealer and have their scanner reprogram something or it will not start. That is why I did not even consider having a Ford in my future. Before I bought the Subaru, I went back to the service department and asked specifically about this, along with a number of other questions that the salesman never had asked of him. Link to comment Share on other sites More sharing options...
Gloyale Posted December 31, 2014 Share Posted December 31, 2014 Does the car have aftermarket stereo or alarm? Aftermarket remote start? Link to comment Share on other sites More sharing options...
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