Car didn't start after sitting with a/c and radio on

Now in my case it's a 2016 Subaru Legacy.


Yesterday I drove a relative to the DMV and while sitting waiting about 30 minutes, I had the car turned off with the key in the 'on' position so I could get a/c going as I listened to the radio.



And as the radio and a/c kept running when it was time to go, the car wouldn't start.



So I turned off the radio and a/c and tried again. And again. And again. Each time, I got fewer electronic signs of life as if the last bit of power was draining from the vehicle. I figured the battery was shot or something.



I bought the car Certified Pre-Owned a year ago this month. It has an OEM Subaru battery dated 3/20 and I've only put 6k miles on it. I called for a jump. While waiting for him, I decided to try the car again after sitting about 10 minutes. It began showing more electronic signs of life (the chimes and more dash electronics came on) and I even heard the engine try to turn when it didn't before and it was just dead quiet. I didn't try starting again after that.



So after I got a jump (thankfully free courtesy of the CPO roadside assistance package from Subaru), I went straight to a Subaru dealership and had it inspected. I pulled in, turned the car off and told them what happened. The service agent gets in and immediately starts the car without issue. They test the battery and electric system and do the all-around inspection of the car that Subaru dealerships offer (all free thank goodness), and tell me the battery is showing 100% charge and all electronics are fine. They didn't want to change the battery because although it is covered on warranty, I didn't have the original paperwork from the Subaru dealership that installed it so I took it home and it's been fine since, though I haven't sat with electronics and a/c on with the key turned in the 'on' position.



The guy who jumped my car says he encounters a lot of Subarus with battery draining issues relating to something about the car's onboard computer not directing the battery to recharge properly. He said some people go through a battery a year. Being a complete layman about such things, I was wondering if anyone else had heard of something like this.


The car is fine but apparently I cannot sit with the engine turned off and radio and a/c running for any length of time.



Until I can get more a grip on this, I'm going to buy a portable jump starter and battery charger. It seems to me like there has to be a flaw in the car to where it has difficulty running electronics with the engine off and retaining enough power to turn the ignition as if it's not recharging appropriately.



I've never seen something like this in my life.

This is simple. You killed the battery by sitting with things on and the car not running. The alternator needs to turn to recharge the battery. The alternator can only turn if the engine is running. Also your A/C wasn't doing anything. You simply had the fan on. The only way your A/C is going to work is, again, if the engine is running.

The reason the car started for the tech was that it is relatively new, and once you got a jump the alternator recharged the battery.

Sitting with the radio and fan on, and the car not running is going to kill any battery. This isn't some crazy Subaru only thing.

Agree with above--

That's why there is an "accessory" position on most ignition switches, to run only the radio and things that don't draw big amps- like a blower motor.

Agree with above--

That's why there is an "accessory" position on most ignition switches, to run only the radio and things that don't draw big amps- like a blower motor.


Well it does have an accessory position but I advanced it to on because accessory didn't offer the option of any kind of fan.



So another question I am researching is the OEM battery's reserve capacity. I'm seeing Subaru owners saying the OEM batteries are garbage in that sense and also in terms of cold cranking amps (odd for cars marketed as snow beasts) that have a CCA rating under 400. I'm having a hard time finding the specs on mine, Subaru parts websites don't say and I can't see what it is when I pop the hood.



I'm thinking I need an upgrade, especially with the multiple complaints I'm finding about lackluster power ratings of Subaru OEM batteries.


I have noticed the installed OEM battery looked small and is about 1/5th smaller than the size of the battery tray.

hey soobie, welcome to Automotive Forums..
Stealthee is correct. without the engine turning the A/C compressor,
the clutch was not spinning; or compressing anything, so just the blower
was moving what was left of the cool air through the ducts, but not 'making'
anymore.. so the blower motor was using alot of amps, as well as the infotainment
console, and possibly your lights were on (as many of your newer vehicles immediately switch either daytime running lamps, or full headlights on) with the key to ON; as opposed to ACCessory..
the minimum ColdCrankingAmps for your subie should be about 450-540..
Cranking Amps is what the battery has to start the car at freezing: 32deg/0 celsius.
CCA is measured at 0degrees/-17.8C
here in colorado you would do better with a 650/700+ in CCA.
you mention the reserve capacity.. this is a minutes amount that the battery can function w/o dying; while running some accessories, to get you home, or to a service station..
a 400cca will be fine for the rest of the summer, but before we get into oct., plan on upgrading.. Subaru tech, may have put a smaller battery into your battery box..
your "Group Size" of battery for your Legacy is a #26; and their are many aftermarket batteries with a superior amount of CCA and reserve cap.; since the 400 probably was a 50-65min. reserve, and an 600 CCA battery will produce volts and amps for 80-90min.
hope this helps..

Much appreciated. So am I even OK running on this battery for now until I decide what to replace it with? I used it today for some shopping and it ran normally. I work a 16 hour shift tomorrow and I assume it won't conk on me. I ordered a portable battery charger/jumper but that won't come until about Thursday.



Also... should I go for an old fashioned acid cell battery or an AGM? It seems that old school is better for Colorado weather.

AGMs are better for cold weather.

soobie,
Stealthee is right again.
while old school batteries are ok (and affordable) as most all people still use them,
AGMs and Gel cells are superior for hot and especially cold weather..
Absorbed Glass Mat batteries cost more; however, they also can last potentially 1-3 yrs
longer in a vehicle (3-5 yrs in a solar home), so this outweighs cost hike..
also, they have the woven mat material inside; as opposed to a lead plate, so
temperatures do not affect them, they do not leak the sulpheric acid if cracked, and
they do not vent harmful chemical vapors; which is why racers love them, as they can mount in trunk, farther away from engine, yet will hold a 100% charge after six plus months with no sulfation, and a higher amp/hour (and usually reserve capacity) ratings, at extreme high or low temps; and 15 times more resistant to vibration (colorado roads anyone)..
i have been using Gates Optima batteries off south broadway since '91; until the rubber company closed their doors, and then i will buy optima or interstate (whichever amazon has on sale); and then rotate my car battery into a solar/wind project (as i've had some optimas last for 15yrs)..
they are definitely worth the money; if you can afford..
and just FYI, autozone (and sometimes others) have a policy:
WITTDTJR (wit-uh-jer)
what it takes to do the job right; and will offer free battery changes, with purchase..
walmart i think is about $7-10..
hope this helps..

I appreciate you guys! AGM it is.

The Subaru OEM is 550 CCA btw.

I'm eyeballing this 850 CCA Odyssey AGM with a 4 year warranty.

if you are shopping locally, o'reilly usually carries optima.
part# red25
about $200.
725 CCA, almost 1000 CA, with a 90min. reserve..
amazon, same pt#, same price, delivered to door; and no core charge..

I'm quite amazed the car's manual doesn't say what size batteries will fit. I see some saying on web forums that the Outback will take a size 34. The Legacy has the same engine.

yes, but the legacy has a lower slung hood..
while the group 34 might fit, it is slightly taller than the 25..
you do NOT want to close the hood and build an arc welder..
go to walmart, or auto store, and measure, as those top posts
do sit a little higher..
25- LxWxH - 9 1/16 6 7/8 7 7/8
34- LxWxH - 10 1/4 6 13/16 8 7/8

it should work; just double check prior to purchase; or install..

yes, but the legacy has a lower slung hood..
while the group 34 might fit, it is slightly taller than the 25..
you do NOT want to close the hood and build an arc welder..
go to walmart, or auto store, and measure, as those top posts
do sit a little higher..
25- LxWxH - 9 1/16 6 7/8 7 7/8
34- LxWxH - 10 1/4 6 13/16 8 7/8

it should work; just double check prior to purchase; or install..


I've seen that someone installed a 34N into a 2016 Outback which is the Legacy's raised wagon twin.

yes, the 34 group battery costs the same, and will have a larger CA/CCA/reserve..
if it will fit; you're gold..
subaru probably installed the same battery tray in vehicles, to keep parts cost down; and
generic means, they are always available, and swappable..
the larger base of the tray is probably for the group 34; and will probably fit;
just make sure of the hood clearance.. a larger, more powerful battery will not do
anything to your vehicle and system; except power it more effectively..
i just haven't worked on a '16 leg; so i cannot tell you what betteries will fit...
.. i did own a '93 subie AWD for many years, and a group 24 (ford) battery squeezed
in to the cavity pretty nice; w/o even needing J-hooks and tie-down bracket..
but then i switched to a Braille Racing battery, that was the size of cigar box, and weighed only 14lbs., and still had over 1000 pulse cranking amps; BUT--
my 93 had WAY less in computized controlled electronics than yours; so stick to
what subaru recommends..

The thing is Subaru lists no recommendations. They have the OEM battery which I think is a 25. The manual says nothing about compatible batteries or max size/height for the battery bay.

No manual is going to have that info for any car. A car is designed for a specific size battery but, but oftentimes other batteries have similar dimensions and post placement and will also work but requires you to do a little research to figure it out.

yes, but the legacy has a lower slung hood..
while the group 34 might fit, it is slightly taller than the 25..
you do NOT want to close the hood and build an arc welder..
go to walmart, or auto store, and measure, as those top posts
do sit a little higher..
25- LxWxH - 9 1/16 6 7/8 7 7/8
34- LxWxH - 10 1/4 6 13/16 8 7/8

it should work; just double check prior to purchase; or install..

I'm not even sure how to check such a thing.

I eyeballed it but have no clue. I'm not sure how to measure or if I can measure. Also the interior of the hood has a heat pad.

I note in Subaru OEM parts, the Legacy and Outback take the same hood and heat pad. I could probably check to see if all body panels are equally shared to get an idea on general dimensions. From what I've seen so far, parts between the two are the same unless it's the rear lift gate or something like that.

Looks like the 16 Outback has the same battery specs as my Legacy.

I'm also seeing different dimensions on different sites. Subaru doesn't list the dimensions for the OEM so I have to use a general Group 25 measure.

Well I found an old school lead Duracell Ultra Gold 34N with 800 CCA for about $150. Not AGM but still... height listed as even 8".

Battery Equivalents website lists Group 35 as having same measurement as Group 25.

Group 25, Subaru OEM is L 9 1/16. W 6 7/8. H 8 7/8
Group 24. L 10 1/4 W 6 13/16 H 8 7/8


I think Subaru puts the smaller choice in to save money but the larger tray gives the option to upgrade aftermarket.

So if this is the case, I'll upgrade to the 34.

Verify terminal/post placement as well.

The Subaru OEM is 550 CCA btw.

I'm eyeballing this 850 CCA Odyssey AGM with a 4 year warranty.

my internet is slower than RTD lightrail to DIA.. just saw this post that came in after other posts.. Odyssey is a very good battery, but slightly over priced..
also, that 850cca is super, but if you decide not necessary; anything above what you have currently: 400-450? it is still working; but anything above 500-600cca would be better for colorado's great 70+degree weather, to -5degree next day drops that sometimes happen more often than we'd like..

and Stealthee is right;
many battery companies make a 24 or 34, and 24R or 34R; meaning the postive and negative posts are reversed for driver or passenger side battery placement; negative posts are almost always placed nearest the fender (ground), so when swinging a wrench you cannot connect POS+ battery post w/ wrench to the fender..

my internet is slower than RTD lightrail to DIA.. just saw this post that came in after other posts.. Odyssey is a very good battery, but slightly over priced..
also, that 850cca is super, but if you decide not necessary; anything above what you have currently: 400-450? it is still working; but anything above 500-600cca would be better for colorado's great 70+degree weather, to -5degree next day drops that sometimes happen more often than we'd like..

My current Subaru OEM is 550. I did note it took longer to start when the temp was about -6 back in late February. As a Denver native, I've seen a cold as -24 straight temp though that cold is rare but I would question the car's ability to turn with that cold.

and Stealthee is right;
many battery companies make a 24 or 34, and 24R or 34R; meaning the postive and negative posts are reversed for driver or passenger side battery placement; negative posts are almost always placed nearest the fender (ground), so when swinging a wrench you cannot connect POS+ battery post w/ wrench to the fender..

Right. This is driver's side so standard.

I'm going to have to call a mechanic about this.

I find this website that says upgrading above OEM can fry components early.



You would rarely find yourself using a battery outside of the specified group size for your car. Nevertheless, with the different car battery varieties and the requirements of a car’s aftermarket audio component, there are some people who might consider a battery with larger dimensions than what is specified for their car. But, group sizes are strictly followed for a reason.

When installing a larger one, the least of your problems would be the battery not fitting the vehicle’s battery tray. Bigger batteries would most likely come in contact with the other metal parts in your car, which increases the risk of a fire. It would also*wear out the original alternator of your car*faster sinceit requires a longer time to keep it charged. Not changing the other electrical components, your wiring, CPU, fuse box, and*the starter would break faster due to the higher amperage running through the circuits. * *

For batteries smaller than the specified group size for your vehicle, there is also a higher rate of wear and tear for your electrical components – particularly the alternator. This is due to the smaller battery using more energy to start the engine, which would have the alternator charge it for a longer time. You would also have to consider if it would have enough power for the underlying electronics on your vehicle – on-board computer, radio, AC, and lights.*

soobiedoobie, it would be great if you posted this other website that had the functions posted about the workings of a battery..
like here:

https://www.autobatteries.com/en-us/how-car-batteries-work/how-a-battery-starts-your-car

but FYI-
(kind of reader's digest)-
when key is turned, battery energizes starter momentarily to crank engine; then that's it.. an alternator then runs your vehicle's components,- AND charges back the battery; it basically keeps a fully charged battery, fully charged.. IF the alternator fails, this is when the battery's 'reserve capacity' kicks in, but seldom ever used..
just like the 'cold crank amps' .. most days (and most city/states) it is above 32degrees. but when it is minus 10, i would much rather have this batt:

https://www.walmart.com/ip/EverStart-Maxx-Lead-Acid-Automotive-Battery-Group-Size-34N-12-Volt-800-CCA/16795242?wmlspartner=wlpa&selectedSellerId=0&wl13=3805&adid=22222222420449455996&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=501107745824&wl4=pla-293946777986&wl5=9028987&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=local&wl12=16795242&wl13=3805&veh=sem_LIA&gclid=CjwKCAjwmv-DBhAMEiwA7xYrd15oeMyMIDLTzu7HSbzIZubHgqwQ5Gm8U7u6L lH76d6AQHMGTujRmxoCuKUQAvD_BwE&gclsrc=aw.ds

than this one:

https://www.walmart.com/ip/EverStart-Plus-Lead-Acid-Automotive-Battery-Group-Size-34/28275671

same size.. same 12V.. different starting/charging characteristics..
i also do not think we ever said if your subie was a 4 or 6 cyl..? i do not recall..
but this could be why bigger battery tray; for a #34 as opposed to a #25; regardless here are some selections of same size batt. w/ different attributes:

https://www.autobatteries.com/en-us/battery-finder-results?recommendationId=68d61830-58ab-4c70-585b-08d8fd2b5900&postalcode=80235

i hope this helps; but still, go to a service center;
or autozone, as they install free with purchase..

That website doesn't know anything. CCA has nothing do with your electrical components. A higher CCA will be better for your alternator because the cranking should be reduced, therefor reducing the voltage drop in the battery, therefor reducing the load on the alternator.

The only thing you have to be conscious of is the height/dimensions so things don't come into contact. That's it. Anyone that says it could fry things has zero proof and is just repeating something their dad's friends brothers friends dad said. A 12v battery is a 12v battery regardless of its size. The CCA is literally the only difference.

soobiedoobie, it would be great if you posted this other website that had the functions posted about the workings of a battery..
like here:



So what I have is a 4cyl 2.5 liter but I'm seeing it takes the same group 25 as the 6 cyl.


The text I posted above came from Curateview by a guy who supposedly has a degree in mechanical and electric engineering. (https://curateview.com/upgrade-car-battery/)He seems quite convinced that getting a larger battery than came with the car is going to cause damage. I don't have that technical background but offhand to me that doesn't make sense. Manufacturers are going to put little batteries in to keep costs down. That doesn't mean anything larger will kill the car.


I've eyeballed the group 25 red top Optima and I decided against it firstly due to the bad reputation they've gotten for quality since moving manufacture to Mexico and secondly, the red top 25 is taller than the one I have right now so I'm not certain of the fit. Third, geez is it overpriced.



I've found AGM and non-AGM in 24 and 24N that fit the height and width of the current battery and are longer but not so long they take up the whole spare approximate 2 inches of room that are vacant in my OEM battery tray.


My list includes:


Bosch S5 non-AGM or S6 AGM

Duracell Ultra Gold non-AGM 34N (WalMart MAXX 34N replacement which others have put into Outbacks)

NAPA Legend Premium AGM



Just started looking into AC Delco or Motorcraft.



I really don't want store brands.

My AGM in both my Stealth and my DD Lancer are Autocraft/Carquest Advance Auto brand batteries and have been great.

As for the article, that guy is literally just a blogger. He has no idea what he is talking about. The fact remains a 12V battery is a 12V battery. Putting a bigger battery in doesn't stress your charging system. The battery is literally just to start the car, and to take big hits/spikes to the system. Once a car starts the alternator keeps it running.

The fact he tries to say amperage is higher with a bigger battery proves he doesn't know anything about cars/car batteries. You'll be 100% fine.

My AGM in both my Stealth and my DD Lancer are Autocraft/Carquest Advance Auto brand batteries and have been great.

As for the article, that guy is literally just a blogger. He has no idea what he is talking about. The fact remains a 12V battery is a 12V battery. Putting a bigger battery in doesn't stress your charging system. The battery is literally just to start the car, and to take big hits/spikes to the system. Once a car starts the alternator keeps it running.

The fact he tries to say amperage is higher with a bigger battery proves he doesn't know anything about cars/car batteries. You'll be 100% fine.

Stealthee uses CarQuest (now Advance Auto) batteries.. i worked for CQ for many years.. their private label oil; on the back (just like NAPA oil) says:
manufactured by Ashland Oil= Valvoline..
same with their batteries; CarQuest= East Penn, which = Deka who makes (among others) Deka, for Harley-Davidson, Deka, for NASCAR, Batteries Plus are Deka, Exide is a sub-company for them, Deka is also Duracell..and more.

naturally their gels are priced steep, AGM is a little better (but they still know it and show in price), and your subaru has been doing fine with lead acid upto now, (is it snowing there? we are getting another foot behind Pikes Peak; and 8 degrees this morning, and my walmart M/C battery will start my Arctic Cat to plow in the a.m.) so; that technology is still in most all vehicles..
and they'll be fine for 5-7yrs in colorado climate..

interstate is still a great battery as well..
there is nothing against a walmart brand; just like all others, will either work, or won't; and will still last 5-6+/-years.. and a $7-10 install in 15 min..
entirely up to you..

yes Optima (since Gates restructure) is more a 1 in every 12/15 batteries is bad, as opposed to the old Optima 1 in every 125 batteries; but the benefit of "store buying" is the store is on the corner wherever you drive..
amazon and 'boutique' batteries are not; but again, most batteries, if they work, are going to work for AT LEAST 3-5yrs maintenance free..
hope this helps.

AGMs are better for cold weather. (https://vehicleconstruction.com/john-deere-1020-for-sale-specs/)


Why did you say that? Can you explain a little bit? I do not know much.