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2017 Subaru Outback, Limited w/Eyesight
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Has anyone replaced the OEM lame battery with a better one?

Was doing some work on our 3.6 and after 2 hours with the dome lights on (yes, my fault for not shutting off) a dead battery quickly ensued. While charging I saw it had all of 490 CCA, which to me says it may be weak and underpowered. Just replaced battery in my older Legacy with whatever Sears unit Consumers liked. Something like 700 CCA and, I perhaps wrongly assume, has more capacity. About $100. The battery tray has ample room it would seem.

Anyone dump the factory battery for a bigger and, I hope,, better one? If so, why? What did you get?
I upgraded to an Optima within the first year.
 

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2015 3.6R Limited w/ES
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3,678 Posts
...The alternator puts out 14+ volts with the car running, but not sure if there is some kind of active regulation going that could be causing it to cut out. I will also put a logging meter on overnight.

Appreciate any input from anyone that has done any diagnostic work for this issue. I tried, but I just can't read through 1800 posts of repeating commentary to find the golden nugget of info that might be in there somewhere. :(
There have been some folks monitoring voltages and one member, who's convinced his vehicle suffers from a random parasitic drain, has been logging for quite some time. His logging hasn't turned up anything unusual, but he seemed tempted to blame the evap test (which happens about 5 hours after the vehicle is parked). Yet still no smoking gun. While I'm not ruling out the chance of some vehicles having defective electronics which could be to blame (e.g., I believe the telematics systems have malfunctioned in some Subarus), I'm far from convinced that this is a widespread issue, in fact I highly doubt it. I think the vast majority of dead battery stories you read about here were never fully diagnosed and likely rooted in one or more of the following:

1. Inconsistent stock batteries from Subaru - despite switching suppliers once or twice through Gen 5, battery reliability appears to have been a pretty consistent problem.
2. Faulty charging logic - this only applies to 2015-17 vehicles and the update has been shown to improve the battery and alternator voltages, but there's some indication that the system still tends to fall short of leaving the battery with a full charge (still much batter than before the update).
3. Folks that don't drive often or take lots of short trips - the negative effects of this were likely further magnified by the faulty charging logic on early Gen 5s. Not only does this predispose some people to no-start events, it's hard on the battery, which can lead to early failure (particularly with the stock Subaru batteries).
4. Various other aspects of these vehicles which can make it easier to accidentally drain the battery, particularly when the driver isn't familiar with some of the newer technology in use, such as push-button start (more than one member has been caught leaving the ignition in ACC when they thought it was OFF).
 

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Depending on your VIN, your 2017 might be eligible for an ECM logic update to improve charging.
Thanks for the link. (I also found it just after I posted.) However, there does seem to be some anecdotal evidence that some folks don't see an improvement even after the update. Anyone with real experience to share with before/after update results?

My vehicle may not be covered under warranty. I'm at 75k and not sure yet if the ext fed emissions warranty covers it as possibly implied in the TSB. I also have a general dislike/distrust of dealerships (call me irrational if you must) and based on other bad experiences, I now do all of my own car repair (I learned everything I know listening to car talk back in the day, haha.) Doesn't mean I won't look into it, but...

I'm also considering just modifying the sensed voltage supplied to the ECM so that it thinks the battery voltage is lower and maintains charging longer. If you're not familiar, search for "alt-s fuse mod" or "alternator voltage booster". Basically, you just add a couple of diode drops to the voltage supplied to the ECM via the battery sensor. You can roll your own or buy the commercial solution.

It may also be possible to disable the charge logic entirely, but that seems more problematic (again based on anecdotal evidence online.)
 

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I'm far from convinced that this is a widespread issue, in fact I highly doubt it. I think the vast majority of dead battery stories you read about here were never fully diagnosed and likely rooted in one or more of the following...
You may be right, but even after a new battery, I'm still having problems. And, there is a lot (again anecdotal) information about this problem online. Enough so that leads me to believe the problem is not isolated. There's even a class action lawsuit now that has combined separate lawsuits on this issue.


If I knew about this all before I bought my new Group 25 replacement, I would have tried a Group 24 or Group 34. I may still try to see if I can upgrade under the warranty, but I kind of doubt they'll go for it.

Regardless, a brand new battery shouldn't be going dead on me with normal driving. And, I should be able to sit and listen to my radio for more than 30m while I wait for my kid at soccer practice. No other vehicle I have owned ever required me to buy a battery backup so my wife wouldn't be stranded on the road somewhere. It's been getting a lot of use.

I'm mostly convinced the problem is charge related. After a hard start the other day, I drove it for an hour around town, then after returning home, I checked and the battery was NOT fully charged. I completely disconnected it, popped the charger on it and it took more than a few amps until it eventually topped off a little over an hour later. I cleaned the terminals so they were nice and shiny and then 2 days later, hard start again.
 

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You may be right, but even after a new battery, I'm still having problems. And, there is a lot (again anecdotal) information about this problem online. Enough so that leads me to believe the problem is not isolated. There's even a class action lawsuit now that has combined separate lawsuits on this issue.

Yep, lots of those out there, but they rarely seem to get very far.

Thanks for the link. (I also found it just after I posted.) However, there does seem to be some anecdotal evidence that some folks don't see an improvement even after the update. Anyone with real experience to share with before/after update results?...
Not sure I recall anyone claiming the update didn't help, but I do recall one or more posts detailing an improvement in alternator voltage. The ECM update (which includes the new charging logic) is covered under the emissions warranty, plenty of reports here about service advisors using that.

It may also be possible to disable the charge logic entirely, but that seems more problematic (again based on anecdotal evidence online.)
Simplest thing to do is to leave the headlight setting in the ON position, but you really shouldn't have to do that to run the radio for a few hours if you're driving the car regularly (and not just a few miles at a time).
 

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2020 Onyx
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Do you have access to 2020 outback wiring diagrams of the same circuit?

Edit - another question - is it true that the Toyota charging system doesn't get to 14.4 volts? My 2020 Outback definitely does, with no mods.

 

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Do you have access to 2020 outback wiring diagrams of the same circuit?
I sent you a PM.

Edit - another question - is it true that the Toyota charging system doesn't get to 14.4 volts? My 2020 Outback definitely does, with no mods.
I seems most newer ECM controlled charging systems use a variety of input parameters to control what voltage the alternator outputs. Not sure about specific voltages or makes/models, but it certainly can vary during operation for any particular system.
 

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2020 Onyx
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The 2020 comes with an "EFB" battery that supposedly has the same charging characteristics as an AGM according to battery manufacturers so maybe the 2020+ won't benefit from the diode?
 

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2016 Outback Premium 2.5 CVT w/EyeSight+SRVD
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I seems most newer ECM controlled charging systems use a variety of input parameters to control what voltage the alternator outputs.
Yes, that's true for the "battery management system" in the 2015-2019 Legacy and Outback. The voltage regulator itself is still embedded in the alternator, but the voltage setpoint for any given set of conditions (e.g. battery voltage, charge/discharge current, and temperature, road speed, throttle position, engine load, etc.) is determined by firmware in the ECM.
 
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The 2020 comes with an "EFB" battery that supposedly has the same charging characteristics as an AGM according to battery manufacturers so maybe the 2020+ won't benefit from the diode?
Sorry, can't really answer that for you. I do know that AGM batteries require different charging characteristics to prolong battery life and giving the ECM a different voltage than actual is not doing your battery any favors. EFB batteries sound like they are closer to standard flooded LA batteries, but that doesn't mean they don't also require something special.
 

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2016 Outback Premium 2.5 CVT w/EyeSight+SRVD
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I do know that AGM batteries require different charging characteristics ...
Some do; some don't. Read the battery manufacturer's detailed specifications to know for sure. (The Deka/Duracell AGM battery I have is fully compatible with the Outback's OE charging scheme, per East Penn [the manufacturer] literature.)
 
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19 2.5i OB LTD w/SSD Strt Twr Brc + OEM 19mm RSB
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It's probable that after taking the battery to a low voltage state, possibly several times, the ability of it to be charged fully ever again is compromised. The battery enters a "death spiral"... I also think it possible that different suppliers of sub-system components, and the lotting of component and module manufacturing, results in modules that don't perform identically, even if they run the same revision of firmware. There's changes to the circuit boards, and the parts used / substituted... On top of that, add in this "intelligent charging". HA!

Get a bigger / better battery, drive the car, and monitor the charging when the engine is running with a 12V USB charger with LED voltage display. You see it indicating less than 14V, you have an issue which will continue to degrade.
 

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I also think it possible that different suppliers of sub-system components, and the lotting of component and module manufacturing, results in modules that don't perform identically, even if they run the same revision of firmware. There's changes to the circuit boards, and the parts used / substituted...
Not at all likely ... at least as long as the battey management system implemented in the ECM is a "closed loop" design.
 
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Not at all likely ... at least as long as the battey management system implemented in the ECM is a "closed loop" design.
Even if closed loop, there are manufacturing differences / sourcing differences on a range of components - even if put through 100% testing can "pass" and ultimately "fail" in the field... If that weren't the case, no one would ever experience module or sub-system failures in any vehicle they've owned, and while I cannot specifically provide incidences in my Subaru Outback, I have experienced issues in other vehicle makes and models over the period I've been a licensed driver. Come to think of it - it's always been in VW assemblies. :oops::LOL:o_O

We don't know the failure modes of this "closed loop" design you are talking about do we? In general, does it fail to a state where charging at a high current is the default? All it takes is an intermittent in one wire, or an out-of-spec resistance because of a cold solder joint or vibration...

I'm still trying to get my head wrapped around someone else's observation that at idle, their battery voltage reads less than 13.8V. That's UMM, C R A Z Y.
 

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2020 Onyx
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I know that this is a Gen 5 thread but the 11.9 voltage I think comes from Gen 6 owners.

Me, @chvvkumar , @ArF193 , @Linkenhoker have all seen 11.9, @weldonjr2001 sees 12.0 so it's not just a spurious result and although I have no documentation on why it happens my theory is that if a car is running and the alternator is turned off, it's a high electrical load and the car is either doing this to 'test the battery' and/or to let the engine consume less fuel at idle, opportunistically engaging the alternator to charge when the vehicle is slowing down. To test this theory we'd need to look at the amps and volts coming out of the alternator under braking and see if it spikes.

But just to reiterate, 11.9 while the car is running doesn't mean that the battery is depleted. When you turn the car off and there's no electrical load you'll see a higher voltage. But I have seen resting voltage as low as 12.1 which is terrible but like many others with low voltage I have not had the car fail to start. Still not happy about it because the battery begins to sulfate when chronically resting below 12.4 volts.

Not sure how relevant this is to the Gen 5 situation.
 

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2015 3.6R Limited w/ES
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Yeah, that's not open circuit voltage, it's under load when the alternator is disengaged. If you search this thread, you'll see the same voltages have been recorded on Gen 5s:

 
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