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Subaru Outback 2015 2.5L
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Been going through these forums for a bit now, and I'd thought I'd sign up and share my observations on the charging algorithm that Subaru seems to have implemented in the MY2015 Outback. I drive a 2.5L premium, which is basically stock except for an aftermarket air filter and some LED interior lights.

Background
Within the last few months, I had to start carrying a second 12V battery in the back to jump myself and I've had to do this 4 or 5 times. Last week, the car started a bit rough which was a bit odd and then I took an hour drive. After that drive, the battery failed to turn over the car which I found very odd with such a long drive. So earlier today, I decided to observe what was happening.

I used the built in service menu to observe the battery voltage. To access that, while the car is on, press and hold the home button and push the tuning knob in 5 times. Then select Function Check (or something similar) and Vehicle Signal. It will show you the battery voltage in the top left corner.

Observation

Keep in mind that I'm driving while trying to observe this so the timings aren't scientific but are close enough. I took a drive of around 45 min which started with city driving, then 10 min of highway and another 10 or city. I drove during the day so only the daytime running lights were on, radio was on, climate control was set to auto at 20C. Nothing else was turned on.

For the first 10 to 15 min or so, the voltage reads 14.4V. After that the voltage fluctuates depending on what is happening:
- Full stop at a light, the voltage falls to 12.1-12.2V
- Hit the gas, voltage is 12.1-12.2V
- Coast the car, voltage rises is to 14.4V

Driving on the highway, the voltage was around 12.5-12.6V. At the 40min mark I noticed the voltage went back up to 14.4V even though I was stopped at a light.

Other things I could do to force the voltage to rise to 14.4V:
- Turn on the rear defrost
- Turn on the HID headlights

Revving the engine while stopped had no effect on the voltage output.
Opening the rear gate had no effect on the voltage output.

Interpretation

My interpretation is that Subaru has implemented an almost hybrid regenerative braking like system for charging the starter battery, after it believes it has restored enough of the initial cranking power used. Probably for helping the mileage (but I've defeated that purpose because I have to lug around an extra battery.)

These results means I should behave differently when operating this car. Counter-intuitively, this means:
- If you are leaving your car on to wait for someone while listening to the entertainment system or leaving the climate control on, the car might not actually be charging the battery but rather still drawing from it.
- If your battery is low and you had to jump start it, don't necessarily rely on the car to charge it back up to full. Either force the alternator output high by loading the car by turning on some gear or slap a battery charger on the battery.

Hope these results help! Feedback welcome.
 

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2012 OB , 2017 Impreza
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I commend you on your astute observations.

Honda has used such a 'regenerative braking' by turning on the alternator to MAX during deceleration for over 15 years.... you do not hear about Honda cars having the same kind of battery issues that the newer Subies are experiencing.

I still suggest that everyone "equalize" their battery at least every 6 months. Equalizing a battery ensures that ALL the cells are working together.

Lets not forget that if any ONE of the cells is allows to get weak.... the ENTIRE battery is done.
 

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96 Leg L, 2.2L Sdn,07 Outback 2.5i Wgn,05 Leg GT Wgn,05 OBXT Wgn
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67 Posts
Been going through these forums for a bit now, and I'd thought I'd sign up and share my observations on the charging algorithm that Subaru seems to have implemented in the MY2015 Outback. I drive a 2.5L premium, which is basically stock except for an aftermarket air filter and some LED interior lights.

Background
Within the last few months, I had to start carrying a second 12V battery in the back to jump myself and I've had to do this 4 or 5 times. Last week, the car started a bit rough which was a bit odd and then I took an hour drive. After that drive, the battery failed to turn over the car which I found very odd with such a long drive. So earlier today, I decided to observe what was happening.

I used the built in service menu to observe the battery voltage. To access that, while the car is on, press and hold the home button and push the tuning knob in 5 times. Then select Function Check (or something similar) and Vehicle Signal. It will show you the battery voltage in the top left corner.

Observation

Keep in mind that I'm driving while trying to observe this so the timings aren't scientific but are close enough. I took a drive of around 45 min which started with city driving, then 10 min of highway and another 10 or city. I drove during the day so only the daytime running lights were on, radio was on, climate control was set to auto at 20C. Nothing else was turned on.

For the first 10 to 15 min or so, the voltage reads 14.4V. After that the voltage fluctuates depending on what is happening:
- Full stop at a light, the voltage falls to 12.1-12.2V
- Hit the gas, voltage is 12.1-12.2V
- Coast the car, voltage rises is to 14.4V

Driving on the highway, the voltage was around 12.5-12.6V. At the 40min mark I noticed the voltage went back up to 14.4V even though I was stopped at a light.

Other things I could do to force the voltage to rise to 14.4V:
- Turn on the rear defrost
- Turn on the HID headlights

Revving the engine while stopped had no effect on the voltage output.
Opening the rear gate had no effect on the voltage output.

Interpretation

My interpretation is that Subaru has implemented an almost hybrid regenerative braking like system for charging the starter battery, after it believes it has restored enough of the initial cranking power used. Probably for helping the mileage (but I've defeated that purpose because I have to lug around an extra battery.)

These results means I should behave differently when operating this car. Counter-intuitively, this means:
- If you are leaving your car on to wait for someone while listening to the entertainment system or leaving the climate control on, the car might not actually be charging the battery but rather still drawing from it.
- If your battery is low and you had to jump start it, don't necessarily rely on the car to charge it back up to full. Either force the alternator output high by loading the car by turning on some gear or slap a battery charger on the battery.

Hope these results help! Feedback welcome.
Wow that's some great research. I really appreciate it don't make sense when I have a low battery problem and I thought I was charging it. Thank you in advance for a lot of Subaru lovers

Sent from my ASUS_P00J using Tapatalk
 

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2015 Outback Premium
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I can verify the OP's observations. I had been having problems with the battery in my 2015 Outback and replaced it with a new Bosh battery. At the same time I put Torque Pro on my tablet just to keep an eye on things. I saw the same voltage variations under similar conditions so I took it to the dealership thinking my alternator was going bad.

Of course, when I got there it was working fine. The service manager set up an appointment the next day. Once again it was working fine. So she told me that if I was out driving and it occurred again to drive straight there and not shut the car off so they could look at it. A couple days later it happened again while I was just a mile from the dealership. Went there and the service manager got their electrical specialist tech and we all went for a ride. The tech observed the voltage swings and explained that it was normal behavior and why it was happening.

His explanation for not seeing it the other times was that I only live 5 miles from the dealership and that wasn't a long enough drive to cause the "conservation" mode. There is evidently a sensor in teh positive wire at the battery this controls this behavior.

 

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'14 Subi OBW, '18 Subi Forester
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Honda has used such a 'regenerative braking' by turning on the alternator to MAX during deceleration for over 15 years.... you do not hear about Honda cars having the same kind of battery issues that the newer Subies are experiencing.
I'm active on the CR-V board, and there are plenty of 'bigger battery', 'repeated dead battery', 'parasitic draw', 'computer controlled charging scheme doesn't work' type threads there too.
 
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On the Super Mod Squad
2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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26,194 Posts
I can verify the OP's observations. I had been having problems with the battery in my 2015 Outback and replaced it with a new Bosh battery. At the same time I put Torque Pro on my tablet just to keep an eye on things. I saw the same voltage variations under similar conditions so I took it to the dealership thinking my alternator was going bad.

Of course, when I got there it was working fine. The service manager set up an appointment the next day. Once again it was working fine. So she told me that if I was out driving and it occurred again to drive straight there and not shut the car off so they could look at it. A couple days later it happened again while I was just a mile from the dealership. Went there and the service manager got their electrical specialist tech and we all went for a ride. The tech observed the voltage swings and explained that it was normal behavior and why it was happening.

His explanation for not seeing it the other times was that I only live 5 miles from the dealership and that wasn't a long enough drive to cause the "conservation" mode. There is evidently a sensor in teh positive wire at the battery this controls this behavior.

the people towing with CVT will like that you got Torque Pro reading the trans fluid temp there, plus the coolant temps. :smile2:


I think there might be a place to set a alarm before the regular dash lights pop on. (like its time to pull over and idle for a while).

http://www.subaruoutback.org/forums/104-gen-4-2010-2014/473457-effects-paddleshifting-cvt-temperature.html
 

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2015 Outback Premium
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the people towing with CVT will like that you got Torque Pro reading the trans fluid temp there, plus the coolant temps. :smile2:


I think there might be a place to set a alarm before the regular dash lights pop on. (like its time to pull over and idle for a while).
Yes, you have to purchase Torque Pro and the ActiveODB plug-in for it to get the CVT readings. With Torque Pro you can set maximum numbers for any of the gauges. When it reaches that point the gauge will flash as a warning. I set mine at 230 which is ~30* lower than the factory alarm.

I have had this set up for a couple months now and am still finding things I can do with it!
 

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2017 2.5i Premium Lapis Blue
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I wonder if the TSB for the charging system eliminates this behavior completely or just alters it? I've never really found out exactly what the TSB changes.
 

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2008 OB Limited 2.5i, Portland OR USA
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I wonder if the TSB for the charging system eliminates this behavior completely or just alters it? I've never really found out exactly what the TSB changes.
This could be sleuthed out by applying the technique @Capeachy has developed to the same vehicle both before and after the TSB update is performed.

Somebody with a lot of time and ambition on their hands should really do this.

What might be discovered is that Subaru overdid it on the part where the battery isn't charged enough during normal operation, to the point where it is run down and any added stress imposed - time, temperature, etc. - results in a no-start condition. I'm sure this is all about the CAFE numbers that they're fighting to keep as high as possible.
 

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Other things I could do to force the voltage to rise to 14.4V:
- Turn on the rear defrost
- Turn on the HID headlights
The rear defrost is a good tip. I could totally see myself popping it on just to top off the battery. Easier than getting stranded or jump starting, but still absurd that it's necessary in the first place.
 

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2017 Outback 3.6R Limited
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Would the voltage behave the same if the car had a brand new battery? Perhaps this behavior is some symptom of the battery dying?
 

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Would the voltage behave the same if the car had a brand new battery? Perhaps this behavior is some symptom of the battery dying?
Yes, In my case I put the tablet and Torque Pro in place after the original battery had died and I replaced it with a new one. I wanted to make sure that nothing happened to the new one.
 

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2008 OB Limited 2.5i, Portland OR USA
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Would the voltage behave the same if the car had a brand new battery? Perhaps this behavior is some symptom of the battery dying?
With a computer in the mix deciding when it's going to suppress charging and when it's going to goose it, anything is possible.

And reverse engineering it in the manner that @Capeachy and @Hal did is about the only way you'll find this information out. That is, other than hacking their code.
 

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2017 2.5i Premium Crystal White Pearl with Ivory Cloth, with Eyesight and self dimming outside mirrors.
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I used the built in service menu to observe the battery voltage. To access that, while the car is on, press and hold the home button and push the tuning knob in 5 times. Then select Function Check (or something similar) and Vehicle Signal. It will show you the battery voltage in the top left corner.
I followed your instructions and had the same results. Except as soon as I could get it back to where I could read the voltage it was reading 12.0. Without input from me that's where it would stay.
 

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2018 Outback Touring 2.5i
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I turned on logging in Torque Pro on my drive home ('18 2.5 Touring). If "Voltage (Control Module)" (PID 42) is the appropriate sensor, I was getting between 13.8 and 14.3 V in 55 miles of 80:20 interstate:city (including stop lights, on-ramps, etc.), and mainly between 14.1-14.2 V. AC and defrosters were off, blower was low-medium. When I shut off the engine, voltage promptly dropped to 12.6 V. So I guess they did change the charging pattern from previous years. (If this is the wrong sensor, then never mind.)
 

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2016 Outback 2.5i Limited
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While getting a 42k service done on our '16 Outback my wife was told there is a software upgrade available to help with battery charging. I'm guessing "help with" means correct the issues. Seems to me this should be a free upgrade as it corrects a problem, but it costs a little over $150.
 

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'15 Outback 2.5i Premium
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I just had this TSB applied a week ago at my 48K service. Too soon to tell, and I don't have OBD logs from before to compare with.
 

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If you don't mind me asking...was the charge for it just over $150? Also since your Outback is near mine WRT to mileage...has it been suggested to you that your front and rear differential fluid and brake fluid needs to be replaced ?

My wife was hit with these suggestions, plus "the cabin air filter needs replacing" at the 42k servicing. We had this air filter replaced at the 30k servicing. So the total was going to be near $600.
 

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The reprogramming charge was $45 (there were two I had done, at $45 each).

I don't remember the schedule for the cabin and engine air filters, but those do need changing from time to time, and I sometimes drive on dusty roads. At the previous service, at Heuberger in Colorado Springs when I was passing through, the service rep said "your cabin and engine filters are OK for now, but will probably need to be changed on or before the next service interval." So I bought one each from their parts department while they were finishing up and replaced them myself just before taking it in for the more recent service. Both were easy (I can give a tip or two). The service guy knew I was transient, so he he wasn't really selling me a service down the road by advising to change "soon", and Heuberger has a good rep on these boards (I can see why!)

F & R diff fluid replacement is not on the 48K-mile service schedule. Me: "I need an oil & oil filter change, please, here's a coupon. I've just changed both air filters, so I don't need those. Can you check these or related TSBs, please, and, if they address these issues on this car, how much will they cost?". He didn't suggest either diff service.
 

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Thanks!!!
I thought the $150+ charge for the update may have been a little high. Plus thought the suggestions about the F&R Diff fluid and brake fluid was "strange" also. I know she's been hit by those suggestions at quick oil change places, but was surprised she got those at a Subaru dealer. Maybe it's just me.
 
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