nmgregoire Posted March 20, 2020 Share Posted March 20, 2020 Our 2019 Legacy's battery has apparently died twice in the past month. The first time, we just thought we had left a light on or something. So the dealership replaced the battery. The second time, we knew it wasn't our fault. The dealership told us that because all "modern" cars have so many electronics, they slowly drain the battery even when everything is "off" if you don't drive it for a few days. Then you've got a dead battery. First of all, that seems like a SEVERE design flaw, if I actually believed. We don't drive our car very often, so not driving it for a week isn't unheard of. Having to go out and drive it for no reason every other day seems ridiculous. I've had "modern" cars (2016 Civic with plenty of electronics) and never experienced or heard of anything like this. What if I have to leave the car in an airport parking lot for a week? Am I just screwed? I suspect there's a real issue here and they either can't find it or are too lazy to. Am I crazy here? Has anyone else dealt with this? Any help is greatly appreciated! Link to comment Share on other sites More sharing options...
Yoda_One Posted March 20, 2020 Share Posted March 20, 2020 (edited) First... You need to drive the vehicle enough to fully charge the battery. When the dealership replaced the battery the high probability it wasn't fully charged and you needed to trickle charge or drive it. When my wife and I retired, our vehicle use dropped considerably and we needed to change the routine so I purchased a trickle charger to compensate for loss of use. I use it as needed since the vehicles are not being started and driven often. I've had "modern" cars (2016 Civic with plenty of electronics) and never experienced or heard of anything like this. What if I have to leave the car in an airport parking lot for a week? Am I just screwed? I suspect there's a real issue here and they either can't find it or are too lazy to. Am I crazy here? Has anyone else dealt with this? Any help is greatly appreciated! I believe you are not fully informed... The alternator is not charging when idling, at stoplights or when at rest. The reason is to save gasoline. With all the electronics, Air-conditioning running directly off the battery instead of the alternator constantly recharging, you need to be aware of the differences and adjust your habits. Edited March 20, 2020 by Yoda_One Laughing at Oneself and with Other is good for the Soul Link to comment Share on other sites More sharing options...
PHDRPH Posted March 20, 2020 Share Posted March 20, 2020 See my post on my 2016 Legacy. I was on my third battery. Even though I only have about 12,800 miles, there is NO REASON THAT SHOULD HAPPEN!! The subaru battery CC is terrible. I finally replaced the battery with a CC over 700. Between the poor batteries and Subaru windshield, I don’t think I would purchase another subaru. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
nmgregoire Posted March 20, 2020 Author Share Posted March 20, 2020 I guess I'll just have to take it for a lengthy drive once a week. I still believe this is a design flaw. Modern engineering can certainly account these shortcomings. Link to comment Share on other sites More sharing options...
ammcinnis Posted March 20, 2020 Share Posted March 20, 2020 (edited) I still believe this is a design flaw. If it were a design flaw, everybody would be experiencing it. Everybody isn't. Even at Subaru's published maximum "dark current" drain (a.k.a. "parasitic draw"), a healthy and fully-charged OE battery will last more than three weeks of inactivity before it is fully depleted (i.e. unable to start the car). You do have to begin with a fully charged battery, though, and an inexpensive "smart" battery charger (a.k.a. battery minder, battery tender, etc.) is a good investment. There are many things that can cause higher than normal current draw while the car is sitting. Besides lights left on, there are several common "operator problems" associated with pushbutton start, if your Legacy is so equipped. There is a lot of information already available on the topic in this forum; Search is your friend. FWIW, in more than 5 years and 50,000 miles I have never had the battery in my 2015 Legacy Premium discharge to the point that it wouldn't start the car. Same for the OE battery in my 4 year old, 42,000 mile 2016 Outback Premium. (Full disclosure: Both OE batteries have now been replaced, but in both cases it was due to electrolyte leakage from case seams.) Edited March 23, 2020 by ammcinnis "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
nmgregoire Posted March 20, 2020 Author Share Posted March 20, 2020 I had a brand new battery. Fully charged. I don't have a pushbutton start. Link to comment Share on other sites More sharing options...
ammcinnis Posted March 20, 2020 Share Posted March 20, 2020 (edited) Ask your dealer to perform a "dark current" test on your Legacy. That will narrow the search for a cause. There are also several threads on this forum about replacing the OE battery with higher-capacity aftermarket batteries. The OE battery is BCI Group 25; both Group 24 and Group 34 are well-known drop-in replacements, usually with substantially higher capacity. For the problems you describe, Cranking Amps and Cold Cranking Amps ratings are far less important than a battery's 20-hour Capacity (stated in amp-hours) and Reserve Capacity (stated in minutes) ratings. Edited March 20, 2020 by ammcinnis "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
nmgregoire Posted March 20, 2020 Author Share Posted March 20, 2020 :Sigh: Why can't cars just work correctly without having to purchase aftermarket items.... Thanks for the info everyone Link to comment Share on other sites More sharing options...
PHDRPH Posted March 20, 2020 Share Posted March 20, 2020 I guess going forward, anyone interested in purchasing a Subaru. Should not buy it blindly. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
chowser51 Posted March 20, 2020 Share Posted March 20, 2020 Do you keep your keyfob near the car when not it use? This caused a drain on my car. I no longer hang the key in the garage with the car and it solved my issue. Link to comment Share on other sites More sharing options...
gathermewool Posted March 23, 2020 Share Posted March 23, 2020 I’ll second getting a cheap battery maintainer. They usually come with a ring-connector harness, so that plugging in and disconnection is as easy as for a table lamp. No settings to deal with on the simpler ones, either. Just don’t start the car and/or back out with it still plugged in! Do you keep your keyfob near the car when not it use? This caused a drain on my car. I no longer hang the key in the garage with the car and it solved my issue. I noticed the same. It never drained our batteries fully, but enough to be noticeable with a simple voltage check. We now keep our key fobs in a metal box in the kitchen island. '15 FB25 Magnatec 0W-20 + FU filter (70,517 miles) RSB, Fr. Strut Bar, Tint, STI BBS, LED er'where Link to comment Share on other sites More sharing options...
ammcinnis Posted March 23, 2020 Share Posted March 23, 2020 :Sigh: Why can't cars just work correctly ... :Sigh: I keep forgetting: It's always the car's fault. "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
WILLINH Posted March 27, 2020 Share Posted March 27, 2020 My 2016 legacy battery died and the car would not unlock with the key. So I went through the trunk.I replaced the battery with a group 34. I then called Subaru to see if they would cover having a tech see why the door would not unlock with the key, after explaining what happened they told me to scan a copy of the battery sales receipt and send it to them they also called my dealer of choice to check on the door and do battery update, So I received a refund for the battery and had everything else taken care of. I had 44,000 and was out of warranty. GREAT CUSTOMER SERVICE!!!! Link to comment Share on other sites More sharing options...
gathermewool Posted March 27, 2020 Share Posted March 27, 2020 That is amazing to hear! '15 FB25 Magnatec 0W-20 + FU filter (70,517 miles) RSB, Fr. Strut Bar, Tint, STI BBS, LED er'where Link to comment Share on other sites More sharing options...
KennyWRX Posted March 28, 2020 Share Posted March 28, 2020 I believe you are not fully informed... The alternator is not charging when idling, at stoplights or when at rest. The reason is to save gasoline. With all the electronics, Air-conditioning running directly off the battery instead of the alternator constantly recharging, you need to be aware of the differences and adjust your habits. Hmmm, nope you are way off. Alternator output is proportional to engine rpm regardless of whether the vehicle is moving or at rest. At idle, the alternator is still providing current, however, it does charge slower. Whether the battery is charging or discharging depends on other electrical loads on the car and whether the sum of those loads exceeds what the alternator is currently providing. If the alt is putting out more that the loads, it is charging the battery, otherwise, the battery is discharging. Link to comment Share on other sites More sharing options...
waldguy Posted March 28, 2020 Share Posted March 28, 2020 When plugged in to an OBDII car monitor, I found the voltage increased to my battery most when slowing down, likely resulting in the most charging during that condition. Maybe someone can comment whether this is indeed the case. My driving style typically avoids short braking times -- I rather allow the car to coast. I don't have the battery update on my ECM, and haven't found a problem with low charges even with the original battery. The car has been sitting for 20 days (some people aren't getting out much lately!!). Voltage on my Redtop is reading 12.15 V. Link to comment Share on other sites More sharing options...
ammcinnis Posted March 28, 2020 Share Posted March 28, 2020 (edited) When plugged in to an OBDII car monitor, I found the voltage increased to my battery most when slowing down, likely resulting in the most charging during that condition. Maybe someone can comment whether this is indeed the case. Yes, that is the way the original (MY 2015-2016) Battery Management System (BMS) was programmed in the ECM. It's a strategy somewhat like regenerative braking in a hybrid or all-electric vehicle: recover some of the kinetic energy in the vehicle while coasting, and use it to maintain battery charge state. You may also observe the BMS allowing the system voltage to drop below 12.6 volts during acceleration. The BMS firmware update per TSB 11-176-17 revises the alternator programming somewhat, resulting in maintaining a generally better battery state of charge without a measurable adverse effect on fuel economy. Edited March 28, 2020 by ammcinnis "If you don't know where you're going, any road will take you there." ~ The Cheshire Cat (Alice in Wonderland) Link to comment Share on other sites More sharing options...
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