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20 Outback Premium; former 19 Outback Premium, 85 GL Wagon, 87 GL-10 Wagon
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My efforts to kill my OEM 620CCA finally succeeded, almost anyway, at 38,500 miles and 21 months. It was still starting, including after shutting down with start-stop, but it was just feeling sluggish. The kicker was that is was constantly charging at 14.1V, never dropping down to the 12.5-12.7V range during long drives like it used to.

Planning a trip to some remote mountains soon and didn't want to deal with a dead battery on the road. Autozone's tester showed it was fully charged but still tested bad, no specific reason. I was considering the "lifetime" battery through AutoNation and my local Subaru dealer, but decided to just go with the 3-year Duralast EFB from Autozone because I like their service and figure it will be easier to find an AutoZone nationwide than it will be an AutoNation dealer that happens to have a battery that will fit a Subaru if it isn't a Subaru dealer themself. Plus, the Duralast EFB I bought from Autozone for my truck has so far outperformed the AGM or any other battery I ever had in my truck, so for now I'm on the EFB bandwagon.

I'm not sure what the rating is on the EFB sold by Autonation Subaru, but the battery I got from Autozone is rated at 650CCA, so a little better than the 640CCA that seems to be doing so well as a replacement from most Subaru dealers. Since I just got the battery I don't really have anything to report on the new one, but I'll be keeping track of the voltage on trips and expect to see it down in the 12.5-12.7 range after achieving full charge, which is exactly what the EFB on my truck has consistently been doing as well. I know many of you don't like that charging profile, but seeing that lower voltage disappear even on long trips in my Outback, combined with what was feeling like sluggish starting, is what prompted me to get a new battery as a pre-emptive strike before my battery totally failed.
 

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20 Outback Premium; former 19 Outback Premium, 85 GL Wagon, 87 GL-10 Wagon
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Yep, that’s the one I got. Autozone does 10% military discount, every little bit helps.

For the do it yourselfer, one of the easiest battery replacements ever, all you need is your 10mm. Nothing needed to be reset in the car, either. I remember having to do the windows after disconnecting the battery in our 19, not so with the 20.

After the battery change it took about a mile for the DTE to register, and a couple minutes for the tpms to display, other than that everything is normal. Now let’s hope this battery lasts longer than 21 months.
 

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2020 Onyx
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13,455 Posts
Are you going to have Subaru of America reimburse you for the battery?
 

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20 Outback Premium; former 19 Outback Premium, 85 GL Wagon, 87 GL-10 Wagon
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Are you going to have Subaru of America reimburse you for the battery?
I’ll ask but they’ll probably say no since I’m at 38,000 miles, even though it’s just 21 months. Replacement batteries are always time with no mileage limit, but it seems that manufacturers like to limit the miles.
 

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Observing the weird alternator patterns mentioned earlier in the thread. Seems like the car likes to push 14.0-14.4 when you’re decelerating, perhaps in anticipation for auto stop (even though mine is not enabled)… I think I will just keep running with the parking lights on.

Typically, I replace my battery proactively after about 5 years of service, so as long as I can make it to that point I will be happy.
 

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2022 OBW, 2008 OBS
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Observing the weird alternator patterns mentioned earlier in the thread. Seems like the car likes to push 14.0-14.4 when you’re decelerating, perhaps in anticipation for auto stop (even though mine is not enabled)… I think I will just keep running with the parking lights on.

Typically, I replace my battery proactively after about 5 years of service, so as long as I can make it to that point I will be happy.
Yep. I noticed that very consistently the voltage spikes to 14.8-15.0 volts when decelerating to a stop. I can only presume it’s in anticipation of the ASS event and the alternator is trying to stuff a quick surface charge on the battery.

Now that ASS defeat has been figured out, we need to figure out a charging system bypass that will force the alternator into staying active so I can have my auto headlamps back. I may start research into this once I get some factory diagrams sorted out.


Sent from my iPad using Tapatalk
 

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Could there be any negative consequences by driving with parking lights on all the time? (Not including forgetting to turn actual headlights on at night)
 

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2021 XT Touring Popular package #2 OEM Hitch
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399 Posts
Could there be any negative consequences by driving with parking lights on all the time? (Not including forgetting to turn actual headlights on at night)
I keep my lights on with everything i drive. Only issue is bulbs and leds burn out faster. But if it prevents a head on crash its worth a few bulbs. Plus state law construction zones you havev to have them on. PA Roads take 15 years to fix then they start over.
 

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20 Outback Premium; former 19 Outback Premium, 85 GL Wagon, 87 GL-10 Wagon
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Second day doing local driving with the new EFB 650CCA from Autozone and the battery is already showing fully charged based on the alternator dropping down to the 12.X range while driving instead of 14.1V; near the end of its life my OEM battery always charged at 14.1V even after hours of driving, that was one of my clues it was dying. Voltage readings at the initiation of start-stop are significantly higher than the original 620CCA ever showed, usually in the 12.7-13.1V range versus 12.2-12.5 with the original battery. After being stopped with the engine off I've seen voltages as low as 12.2 after about a minute, but the engine still re-cranks very quick and strong. I used to see as low as 11.7V with the OEM battery after a minute of start-stop and it used to start strong as well. So basically I'm seeing comparable if not better performance than when the OEM battery was new, but the voltages from the aftermarket battery are about 0.5V higher.

I have to give Subaru's system credit for sensing the weaker OEM battery as it aged and inhibiting start-stop, because with the new aftermarket battery start-stop is activating much more frequently. When I replaced the battery a couple days ago it had never actually failed, but just felt weak like it was barely turning the engine over, so I did a preemptive replacement. As an added bonus, the stronger cranking from the new battery makes start-stop even smoother because the engine restarts so quickly, no delay whatsoever starting from a red light and immediately accelerating, actually ahead of traffic in adjacent lanes.

I know many of you don't use start-stop at all, so it will be interesting to see if the battery life is better or worse for those who do let start-stop do its thing and those who don't. Mine lasted 20.5 months using start-stop; there seems to be many on here who have replaced batteries much sooner whether they use start-stop or not.
 

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2020 Limted XT Black/Ivory
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Second day doing local driving with the new EFB 650CCA from Autozone and the battery is already showing fully charged based on the alternator dropping down to the 12.X range while driving instead of 14.1V; near the end of its life my OEM battery always charged at 14.1V even after hours of driving, that was one of my clues it was dying. Voltage readings at the initiation of start-stop are significantly higher than the original 620CCA ever showed, usually in the 12.7-13.1V range versus 12.2-12.5 with the original battery. After being stopped with the engine off I've seen voltages as low as 12.2 after about a minute, but the engine still re-cranks very quick and strong. I used to see as low as 11.7V with the OEM battery after a minute of start-stop and it used to start strong as well. So basically I'm seeing comparable if not better performance than when the OEM battery was new, but the voltages from the aftermarket battery are about 0.5V higher.

I have to give Subaru's system credit for sensing the weaker OEM battery as it aged and inhibiting start-stop, because with the new aftermarket battery start-stop is activating much more frequently. When I replaced the battery a couple days ago it had never actually failed, but just felt weak like it was barely turning the engine over, so I did a preemptive replacement. As an added bonus, the stronger cranking from the new battery makes start-stop even smoother because the engine restarts so quickly, no delay whatsoever starting from a red light and immediately accelerating, actually ahead of traffic in adjacent lanes.

I know many of you don't use start-stop at all, so it will be interesting to see if the battery life is better or worse for those who do let start-stop do its thing and those who don't. Mine lasted 20.5 months using start-stop; there seems to be many on here who have replaced batteries much sooner whether they use start-stop or not.
I usually turn start stop off and mine died in 18 months and 18k
 

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2020 Outback Premium Dark Grey V4 cyl
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I keep my lights on with everything i drive. Only issue is bulbs and leds burn out faster. But if it prevents a head on crash its worth a few bulbs. Plus state law construction zones you havev to have them on. PA Roads take 15 years to fix then they start over.
I do this too. Considering that its becoming more commonplace to not look when changing lanes or pulling out of lots. You can see the lights before hearing the horn or seeing me coming up.
 

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I was curious to compare alternator battery charging between my 2020 Outback with AGM Battery and my wife's 1998 Legacy Wagon with standard lead acid battery. I used my Lascar EL-USB-3 data logger to record voltages on a short trip for both. Both batteries began and ended fully charged. Attached are the graphs for each.

A difference that stands out is when charging, the Outback hovers around 14.3V with peaks to 15V while the Legacy hovers around 13.7V with peaks below 14V.

My wife drives less than an hour a week and the battery remains at or near fully charged. Batteries have been lasting about 5 years in Pennsylvania so not a lot of high temperatures reducing battery life. This 1998 Legacy Wagon has 125K miles with no major repair. Just a little rust we had fixed and the head gasket weeps a little oil. She doesn't want a new car.

I've been driving my Outback several times a week for at least 2 hours a week total. The battery remains at or near fully charged. On some longer drives, the voltage drops to about 13V presumably to protect the battery from over-charging. On a 1.5-hour trip with the battery starting at 12.5V, after 20 minutes of charging at 14.3V, the voltage dropped to 12.7-12.8V (with several spikes to 14V) for the remainder of the trip. This implied that the alternator was supplying all the power to the vehicle and the battery was neither being charged or discharged.

On a dozen or so voltage logs I've been looking for a pattern of voltage drop when the battery is fully charged but have not found one. On one highway drive, the voltage was locked on 14.35V for 1.5 hours with no spikes and 80F outside temperature. The car then sat parked for 3 hours at 13.0V. This made me think of the possibility of over-charging.

I once logged the voltage for one week just sitting in the garage unlocked. The voltage dropped from 12.85V to 12.55V. It was a steady but decreasing drop with no spikes (like a spike voltage drop that would occur if the EVAP system kicked in).
 

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2020 Premium Tungsten metallic w/ option pkg 15 and tow hitch, foot illumination lights, skid plates
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OEM battery sat at the airport again, this time for eight days. Started to curse Subaru when the rear hatch did not open but remembered I had put the key fob to sleep. Started right up with no problems. 15 month old battery, 16k mi.

For Daniel, I only use stop/start at long traffic lights and construction zones.
 

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2020 Outback Premier XT (Canada)
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I have the original Suburu battery 620CCA, and only 3528 km's. I have start stop disabled by the device. I drive with headlights on. Everything working ok. But I am wondering 1.5 hour drive at highway speeds, it is always charging at 4.1/4.2. After being stopped at the end of the trip shows 12.1. Just wondering if it is hard on the alternator constantly charging like that? and 12.1 at the end seems to low, headlight and radio off.
 

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2022 Limited Magnetite Gray Metallic
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I have an Outback Limited 2022 and the battery died on me after 3 days. I didn't even have 200 miles on the car. Called Subaru Roadside Assistance and got a jump and went immediately back to the dealer who told me my battery was fine. I drove it home and the battery died again 2 days later. Went through the same experience at the dealer. It was even suggested to me that I remember to put my foot on the brake before trying to start the car!! If looks could kill... After the third time of having the battery die, my temperament went hot and I made them keep the car and give me a loaner so they could track down the battery drain issue. After a week they gave it back to me and finally agreed the battery was bad and they replaced it. I've had it back almost two weeks now and it has started each time but I can't help but have a nervous feeling whenever I press the Start button.
 

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2020 Onyx
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Just wondering if it is hard on the alternator constantly charging like that? and 12.1 at the end seems to low, headlight and radio off.
We're in uncharted territory and only via us owners sharing our own experiences with as much detail as possible can we try to elucidate what is happening.

12.1 is too low, so if you're saying that your battery refuses to charge despite showing 14.x volts for 1.5 hours of driving with your headlights on then I suspect a defective battery instead of one being overcharged. Even a chronically overcharged battery will have a high surface charge but will very rapidly lose voltage under load. I presume your 12.1 test was with no load? Did you use a multimeter with the engine off?

If the car was "on" but the engine not running, and you're looking at voltage via the infotainment system, it's under load because the car's electronics are power hungry even without the radio and headlights and I'm not sure how much voltage sag to expect.

@carjoy do you know if your replacement battery was the 640 or 620 CCA battery? If you're not sure you could take a photo of your new battery and share it.
 
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