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Car Forum / Subaru Cars / August 2008Smart voltage regulator (NOT) = flat battery
I frequently end up with a flat battery in my Forester05, despite the garage test rig reporting that the alternator and battery are in perfect condition. What am I doing wrong ? I am driving without the heater fan or sidelights on. If you run the battery low by parking with the lights on (say), there is no way the battery will ever recover unless you drive with the fan on. (I am not joking). Short journeys or long. Charging lead-acid batteries is not rocket science, all you do is put 14.6v across the terminals until the charge current shows it to be fully charged, then maintain a 14.2v trickle charge. Try plugging a voltmeter into your cigar lighter socket and watch what happens on your lovely Subaru, then compare it to any other make. > I frequently end up with a flat battery in my Forester05, despite the > garage test rig reporting that the alternator and battery are in [quoted text clipped - 10 lines] > voltmeter into your cigar lighter socket and watch what happens on > your lovely Subaru, then compare it to any other make. Hmm, Sounds like you have bad battery. Checked each cell with hydrometer? Probably one cell is sick. > Charging lead-acid batteries is not rocket science, all you do is put > 14.6v across the terminals until the charge current shows it to be Hi, Have you been charging the battery externally when it's gone flat, or simply relying on the alternator to do it? If you're suffering from a weak or sick battery (see Tony's note on a bad cell), you're putting extra strain on the alternator. I've seen more than one alternator "give up" on a bad battery: the owner puts in a new battery and hardly any time later, it's flat cuz his alternator's gone bad as well. It's sorta "chicken and egg" diagnosing the "real" culprit! I've also had good results when buying new batteries if I put a trickle charger on overnight the first night the battery's in the vehicle. Again, the idea is to minimize the strain on the alternator in case the battery has been sitting on the shelf a while and has self-drained a small amount. Rick >> Charging lead-acid batteries is not rocket science, all you do is put >> 14.6v across the terminals until the charge current shows it to be [quoted text clipped - 17 lines] > >Rick As I said in my first paragraph, the Subaru test rig reports both battery and alternator in perfect condition. I have also tried a new battery because I initially thought it was the obvious solution. The problem is simple, the system does not hold the battery teminals above 14.1v (as per battery manufacturer's recomendation) if you do not keep the blower or the lights on. The Impreza08 car they lent me performs in a very similar fashion, but differs in that it keeps returning to charging (14.6v) every two minutes, whereas the Forester05 gives up after a couple of bursts. The real question is why does the voltage remain permanently in the 14.2 to 14.7v range when I do have the fan switched on ?? It is nothing to do with the extra load requirement, the facts are simple - over 14.1v = current into the battery, below this = no charging taking place, despite the battery being only 50% charged. > The problem is simple, the system does not hold the battery teminals > above 14.1v (as per battery manufacturer's recomendation) if you do > not keep the blower or the lights on. Hi, I had an early water-cooled VW that wouldn't charge above about 14-14.1 volts, w/ attendant short battery life. Turns out VW sourced their alternators that year from Motorola, and the following year from Bosch cuz of recurring similar problems w/ the Motorola units. I replaced the alternator w/ a Bosch, and the problem went away. I'm gonna wonder out loud if Subaru may have gotten a "bad" batch of alternators? The dealer told me the same thing you were told: "It all checks out ok." Well, then why do I have flat batteries? "Uhh..." Also, bad grounds were once problematic on a lot of German (and English) cars--they'd have the ground wire screwed down onto a painted surface instead of having bare metal to bare metal contact. Have you checked the connection where your battery ground wire cable meets the body/chassis? I'm also gonna wonder out loud if your fan's providing enough ground to allow proper voltage output? I'm not sure exactly how various alternators are wired up, but it seems from observation some are more tolerant of the voltage range they'll work w/ than others. Otherwise, it's still a mystery to me. Rick >> Charging lead-acid batteries is not rocket science, all you do is put >> 14.6v across the terminals until the charge current shows it to be [quoted text clipped - 17 lines] > >Rick I have charged it on the bench on each occasion it went flat. >>>Charging lead-acid batteries is not rocket science, all you do is put >>>14.6v across the terminals until the charge current shows it to be [quoted text clipped - 19 lines] > > I have charged it on the bench on each occasion it went flat. Although I don't hang out at Forester specific forums, I'd expect this to be a widely reported problem if ALL Foresters exhibit it. So, I'd have to say the shop has not done proper/enough troubleshooting. Did you buy the car used? Is the V belt in good condition/tight? I agree that charging batteries is not rocket science, but there are a LOT of odd ways that system can fail in a car. My daughter's 95 maxima has an oil leak that very gradually destroyed her alternator. While doing so, we had many very strange problems with intermittent 'flat' batteries. And batteries (for cars) can not tolerate many cycles to 0 volts before their longevity is also compromised. That created another level of confusion. Add to that some parts of the country are so hot average battery lifespan is well under 3 years.... if you frequently need to idle for long periods of time with accessories on, investigate using a smaller alternator pulley. I dunno Carl  Signatureto reply, change ( .not) to ( .net) >>>>Charging lead-acid batteries is not rocket science, all you do is put >>>>14.6v across the terminals until the charge current shows it to be [quoted text clipped - 41 lines] > >Carl Thanks for all the suggestions in this thread, everything is pristine in the engine compartment, earth lead tight, etc, and the fault is identical with a new battery (I tried that first, but have now swapped back). The crux of the matter is that the charging system behaves perfectly if I have either the fan or the side lights on (eg: voltage above 14.1 at all times). Secondly, an Impreza08 they lent me behaves in a very similar manner wrt lights/fan on or off. The only difference was that without the fan or lights it did go down to 12.8v quite regularly but kept trying again, whereas mine stays off charge after the first five minutes. The alternator is controlled by the ECU, hence the "smart", but I reckon they had a software bug for a couple of years. I read this one yesterday and thought this guy is full of it cause things don't add up. I have a built in volt meter on my car and it reads just fine. Your cig lighter may be corroded inside or something like that. Also, it sounds like you may have a bad connection somewhere in your battery terminals. Ever take them off and scrap the old lead off the contact areas and replace them? I put a few drops of motor oil on top of each one and the car rattles it all over to protect them from corrosion after cleaning. I say this, because it sounds like your battery is not getting charged, that's why it drains so fast. Oh, and all I can think of is the fan is causing enough current to pass the bad connection to cause it to also let it charge, so that can make some sense too. SignatureBob Noble http://www.sonic.net/bnoble >I frequently end up with a flat battery in my Forester05, despite the > garage test rig reporting that the alternator and battery are in [quoted text clipped - 10 lines] > voltmeter into your cigar lighter socket and watch what happens on > your lovely Subaru, then compare it to any other make. Intermittent loose/cracked battery cell? It's happened to me and had everyone stumped for a while. Worth checking. -C- >I read this one yesterday and thought this guy is full of it cause things > don't add up. [quoted text clipped - 31 lines] >> voltmeter into your cigar lighter socket and watch what happens on >> your lovely Subaru, then compare it to any other make. >I frequently end up with a flat battery in my Forester05, despite the > garage test rig reporting that the alternator and battery are in [quoted text clipped - 10 lines] > voltmeter into your cigar lighter socket and watch what happens on > your lovely Subaru, then compare it to any other make. You haven't said what the charging voltage reads with the engine running and everything else off. Is it higher than battery voltage with the engine off? Is it higher at 2000 rpms than at idle? Have you bothered to check the current draw when the engine is off and all accessories, interior lights, etc. are off? Disconnect the negative terminal and put an ammeter between the post and the terminal. After waiting several seconds for any capacitors to recharge, the current should be less than 0.05 amps. Anything higher, start pulling fuses one by one until you discover the circuit with the problem. Bob >>I frequently end up with a flat battery in my Forester05, despite the >> garage test rig reporting that the alternator and battery are in [quoted text clipped - 14 lines] >running and everything else off. Is it higher than battery voltage >with the engine off? Is it higher at 2000 rpms than at idle? All modern cars including Subarus can charge at max rate when the engine is idling. Increasing the revs makes no difference to any of them including mine. The charging voltage is 14.7v during the periods when it is delivering any charge to the battery. >Have you bothered to check the current draw when the engine is off >and all accessories, interior lights, etc. are off? [quoted text clipped - 4 lines] >start pulling fuses one by one until you discover the circuit with the >problem. There is absolutely no need to measure current flow, the charge rate of the battery is entirely down to the voltage across the terminals. 14.2v for minimum trickle charge recommended for normal use when fully charged, 14.7v for a healthy charge rate. The system is perfectly capable of doing this continuously, indeed it does exactly this with the lights on. It is only in conditions of minimum load that it fails to maintain even a trickle charge, despite the battery state being below 50%. Gilbert >Bob >>>I frequently end up with a flat battery in my Forester05, despite the >>> garage test rig reporting that the alternator and battery are in [quoted text clipped - 44 lines] > >>Bob If this were any other make of car, I'd say you had a bad voltage regulator on your alternator. Has your garage tried installing a new or rebuilt alternator as a test? It's one of the benefits of going to a dealer with these problems. Yes, I'm aware that alternators on this car cost upwards of $450 list. You mentioned in another post that you think the ECU controls the alternator output. I think you're mistaken. The voltage regulator on most modern alternators consists of a small logic board, not just static components. Hence the term "smart". If the swapped alternator behaves properly, and you're not covered under warranty, you might be able to save $$$ by replacing just the voltage regulator, only (!) $170 list. Bob >>>>I frequently end up with a flat battery in my Forester05, despite the >>>> garage test rig reporting that the alternator and battery are in [quoted text clipped - 61 lines] > >Bob The dealer told me the ECU was the voltage regulator. The car is still in warranty (just) and I am talking to the directors at the dealership to get them to accept the fault. It would be nice if it was the alternator, but my suspicions are aroused by the fact that it behaves perfectly with the fan or lights on. The other day I stopped at the end of a trip leaving the radio on for 15 minutes before re-starting (ie: didn't go through the 'off' posn). The battery volts never went above 12v the whole way home. I hope it is repeatable. It would be really nice if someone else could do the same check as me, I guarantee you will be surprised by the fluctuations - who knows, maybe they are all like this ? Gilbert >>>>>I frequently end up with a flat battery in my Forester05, despite the >>>>> garage test rig reporting that the alternator and battery are in [quoted text clipped - 78 lines] > > Gilbert If you reported this problem before your warranty ran out, then you're covered. Also, I believe your dealer is mistaken about the ECU controlling the alternator. You wouldn't have a design with two methods of voltage regulation, too complicated. Since the function of the voltage regulator is to control the alternator output based on system load and yours doesn't respond the way it should, then it should be a no-brainer to put in a working alternator and compare it. Perhaps it's failing when the engine gets good and hot and your dealer is testing it after it's cooled off. They could, if they wanted to, hook you up with a portable ODBC II monitor and monitor the system voltage level while you have the car. When they play it back, they'll see what you're talking about. But trying a replacement alternator costs them nothing but the time to install it. If it's not the solution, they can put it back on the shelf. Bob >>>>>> I frequently end up with a flat battery in my Forester05, despite the >>>>>> garage test rig reporting that the alternator and battery are in [quoted text clipped - 100 lines] > > Bob Hi, I think the dealer techs ae incompetent. Time to try another dealer. I just talked to the Subaru importers, and they know all about this problem, including having looked for ways of fixing it without modifying the ECU software. They can offer no solution other than driving with the fan or lights on all the time. Apparently it affects all models since 2004, and is due to trying to get the best results from carbon emission tests by keeping the generator off-load. Gilbert. >>>>>>> I frequently end up with a flat battery in my Forester05, despite the >>>>>>> garage test rig reporting that the alternator and battery are in [quoted text clipped - 102 lines] >Hi, >I think the dealer techs ae incompetent. Time to try another dealer. > I just talked to the Subaru importers, and they know all about this > problem, including having looked for ways of fixing it without [quoted text clipped - 111 lines] >>Hi, >>I think the dealer techs ae incompetent. Time to try another dealer. I have yet to experience a dead battery (due to my own negilgence OR the 'smart voltage regulatoer' issue you mention) in my '06 WRX. If the system was incapable of keeping the battery charged, shouldn;t I have had a dead battery several times by now? I'm in the US - are you? Could this be specific to another market? Carl Signatureto reply, change ( .not) to ( .net) >> I just talked to the Subaru importers, and they know all about this >> problem, including having looked for ways of fixing it without [quoted text clipped - 3 lines] >> from carbon emission tests by keeping the generator off-load. >> Gilbert. The needle on my BS meter just went into the red zone >> I just talked to the Subaru importers, and they know all about this >> problem, including having looked for ways of fixing it without [quoted text clipped - 120 lines] > >Carl I am in UK, so quite possibly the US market is different. Do you have charges based on CO2 emissions ? Are you using daytime driving lights, or aircon frequently ? When I talked to Subaru UK they were quite open about it, in fact I only had to say I was monitoring the battery voltage and they went on to describe exactly what I was seeing, and the things they had tried while trying to fix it. Gilbert >>>I just talked to the Subaru importers, and they know all about this >>>problem, including having looked for ways of fixing it without [quoted text clipped - 131 lines] > > Gilbert Interesting. Perhaps posting this at www.ulimatesubaru.org and www.nasioc.com and asking other UK/EU owners for thier experiences in this line would be helpful. WE do have DRLs but I know of no seperate environmental controls/taxes involving CO2. Maybe someone else here has more specific knowledge or another Brit will chime in. Carl Signatureto reply, change ( .not) to ( .net) >> I just talked to the Subaru importers, and they know all about this >> problem, including having looked for ways of fixing it without [quoted text clipped - 134 lines] > > Carl Hmmmm, Really? 3 Subaru cars in my family all later than '06 don't have that problem. Driving with lights on? We have DRL. Fan on? most of time it's on by default. Lemme see, typical alternator is 3 phase rull wave rectified and it's output is controlled by field coil current supplied by imbedded regulator. If yoy measure voltage going to F terminal of alternator, you'll see whether it is charging or not and how hard it is charging. As simple as that. >>> I just talked to the Subaru importers, and they know all about this >>> problem, including having looked for ways of fixing it without [quoted text clipped - 143 lines] >alternator, you'll see whether it is charging or not and how hard it is >charging. As simple as that. Sorry, the field current is definitely controlled by the ECU since 04. Monitoring the field current is an indication of the current being delivered by the alternator, yes, but not an indication of battery charging current. The voltage across the battery terminals shows this. I posted one reply at the top (sorry) - here it is again: I just talked to the Subaru importers, and they know all about this problem, including having looked for ways of fixing it without modifying the ECU software. They can offer no solution other than driving with the fan or lights on all the time. Apparently it affects all models since 2004, and is due to trying to get the best results from carbon emission tests by keeping the generator off-load. Gilbert > Sorry, the field current is definitely controlled by the ECU since 04. > Monitoring the field current is an indication of the current being > delivered by the alternator, yes, but not an indication of battery > charging current. The voltage across the battery terminals shows this. Hi, Something doesn't pass the "sniff test" here. Even the inafamous old positive earth Lucas systems weren't any more bass-ackward than that idea... dunno how the rest of the world runs their domestic market alternators, but I'd be hard pressed to think of one, domestic or imported, we have in the US today that doesn't have an integral voltage regulator. Now, I'd understand the ECU monitoring output voltage so it has a base line for comparison when it receives its various signals from this sensor and that, but using the ECU to do the job of the voltage regulator makes zero sense to me at this moment. Maybe I'm missing something important? IF the alternator IS putting out adequate current and voltage, but you're not getting what's required at the battery, WHERE is the loss? That's the question I'd be asking myself if it were my car. Rick >> Sorry, the field current is definitely controlled by the ECU since 04. >> Monitoring the field current is an indication of the current being [quoted text clipped - 19 lines] > >Rick Subaru tell me the alternator is taken off-line a.s.a.p so that it presents no load to the engine during the emissions test, thereby getting a better score. They say there is no voltage regulator inside the alternator because the ECU controls the field current. They also tell me that turning on the blower to its lowest setting is programmed to restore normal generator action. I already proved this myself, and driving lights will do it also. Don't forget this is an 05 car in pristine condition, and it passes the Subaru electronic test equipment run with flying colours. Bottom line is if you have an 04 or later car, and rarely use the fan or the lights, you end up with a flat battery - believe me, I know. Gilbert. >>> Sorry, the field current is definitely controlled by the ECU since 04. >>> Monitoring the field current is an indication of the current being [quoted text clipped - 36 lines] > > Gilbert. Call up the Subaru parts catalog for your vehicle (at the dealer or online) and under "Alternator" you'll see a reference for a voltage regulator. So "they" are mistaken. >>> Sorry, the field current is definitely controlled by the ECU since 04. >>> Monitoring the field current is an indication of the current being [quoted text clipped - 35 lines] > > Gilbert. Hmmm, You and your deler both are full of it? What are you smoking? >> Sorry, the field current is definitely controlled by the ECU since 04. >> Monitoring the field current is an indication of the current being [quoted text clipped - 19 lines] > > Rick Hi, You mention Lucas? That POS! Their wanna be alternator which needed polarization when alternator is replaced like old generator. What wonderful design it was. I had to redo their regulator to correct that BIG design fault. It took me one week end to figure that our for my neighbor who lost charging current after replacing dead alternator. Doesn't Lucas mean knight of darkness something like that?, LOL! Sorry for top posting. Instead of insulting Gilbert, do as I did yesterday and google "ecu control field current alternator" or similar. The ECU does indeed control the field current on many alternators these days. The idea is to effectively turn the alternator "off" or control it to only produce the current actually needed, apparently by applying square wave pulses of varying width as field current. It will turn the field off at full throttle to lessen the load on the engine, for example, when you have drive by wire throttle. That started in 2004 on Legacies, dunno about the rest of the line. The ECU gets its electrical load info from the body control modules, electronic blocks that react to switch settings on the dash, steering wheel, climate control and the RFID keyless entry system. My Legacy has several of these modules up behind the dash, and you have to add a couple more if you want memory on your power seats and remote start. Amazingly, Subaru expects you to hold these extra things in place with plastic ties around the steering column, and the wiring makes my head ache. Got the .pdf for installing the remote start from subarugenuineparts online, and decided I can brave the snow instead! The voltage regulator itself is of course still in the circuit to control the voltage produced after the change from 3 phase AC to DC at the current output prescribed by the ECU. What Gilbert has discovered in his particular car is that unless there is a minimal load at all times, like the fan, or here in Canada DRLs, the system goes into some kind of funk mode and allows the battery to go flat. I guess the solution in his case is to always run a load. I assume something else is wrong, maybe with his ECU and how it interfaces with the alternator, because one would hope that Subaru would have covered the scenario where there is no electrical load beyond the ignition system. But maybe not. The dealer should know more, but we have all run unto dumb dealers. Bruce Armstrong >>> Sorry, the field current is definitely controlled by the ECU since 04. >>> Monitoring the field current is an indication of the current being [quoted text clipped - 26 lines] > who lost charging current after replacing dead alternator. > Doesn't Lucas mean knight of darkness something like that?, LOL! Thanks Bruce, much appreciated. Gilbert. >Sorry for top posting. > [quoted text clipped - 65 lines] >> who lost charging current after replacing dead alternator. >> Doesn't Lucas mean knight of darkness something like that?, LOL! > The ECU does indeed control the field current on many alternators these > days. The idea is to effectively turn the alternator "off" or control it to > only produce the current actually needed, apparently by applying square wave > pulses of varying width as field current. It will turn the field off at > full throttle to lessen the load on the engine, for example, when you have Hi, So what you're saying is the car runs off battery power at times, alternator power at others? The fact somebody does something a particular way doesn't automatically make it a good idea, and, sadly, it's my opinion Subaru HAS bought into a few "less than perfect" ideas in the past. If I understand what you're describing, I'd like to meet the engineer who came up with this. He should be hung by the family jewels for such a thing... Rick >>>> I just talked to the Subaru importers, and they know all about this >>>> problem, including having looked for ways of fixing it without [quoted text clipped - 151 lines] > > Gilbert Hi, You are full of it. You don't even know what you are talking about. Amount of field current controls the output of alternator. It's closed loop servo kinda circuit if you see this electro mechanical device as a electrical simulation. Read your post, ---field current is an indication of the current deliverd by the alternator---- What does that suppose to mean? Do you know what field coil does? Do you know what stator windings do? I think your Subie dealer is full of it too. I live in Foothills in Western Canada. If charging system does not perform well we can even start our cars in the morning with dead battery with slush formed inside. Poential difference(voltage) makes the current flow. Ever looked into dynamic parameters when alternator is under load and charging at the same time. Battery voltage sensing line, F terminal, lternator output terminal, temerature compensation status, etc. with proper instrument. >>>>> I just talked to the Subaru importers, and they know all about this >>>>> problem, including having looked for ways of fixing it without [quoted text clipped - 166 lines] >output terminal, temerature compensation status, etc. with proper >instrument. Ever got out of your armchair and put a digital voltemeter across the battery ? What do you see ? 14.5v ? 12.5v ? Do you know what these two voltages mean ? Can you even turn your drls off ? Why would Subaru admit to this problem if it didn't exist ? Gilbert |
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