Subaru Ascent Forum banner

Battery issues

72K views 117 replies 43 participants last post by  misikoff 
#1 ·
Left car parked at a hotel a week at Christmas. When arriving back to hotel on Christmas night, the battery was dead. Waited a couple hours for repairman to come and start car. (Never will be without jumper cables again) Finally got car started to discover we must have bumped side door light, as it came on after jumped. Figure this was our fault, as it was there for a week. A few weeks later we drove to FL and spent the night in another hotel. Coming out in the morning, the car barely started. I checked to make sure I had not left anything on. Nothing was on. Car is normally parked in garage and didn't have any more problems. A month later, I was searching for papers in the glove box around 6 in the evening. Forgot to close lid. Next morning around 7:30, I ran out to leave, and the battery was dead. Just doesn't seem right that the battery should be dead from a light in the glove box being on for 13 1/2 hours. Thoughts?
 
#3 ·
I'm guessing that the week with a light on drained your battery to the point of damage. The jump start and drive brought it back to charge, but the effective Cold Cranking Amps may have been impacted permanently. Then normal starts succeeded, but with little headroom. Then for whatever reason the night at the hotel was stressful, and showed as a struggle to turn over the next morning. Then the glove box pushed an already damaged battery over the edge. IMO.

You can have the dealership test the battery capacity / effective CCA. Running down car batteries (as opposed to something like marine batteries) is really bad for them.

F.S.
 
#4 ·
The OEM battery is pretty bad to behind with. Im looking to purchase a replacement as soon as I figure out what I can upsize in there from Costco. I usually get 4-5 years out of them.

I believe its a Group 31 currently in there.

I've noticed it dropping under 12 volts after a few days of sitting which is 40%-50% full. Its just waiting to strand me somewhere.
 
#5 ·
I believe the Ascent has an unusually large parasitic current drain. It's normal these days for cars with sophisticated electronics to have parasitic drains, but my Ascent's battery voltage routinely drops to 11.5 volts after several days of non-use. I've had to charge it several times over the last few months. I'm now keeping a close watch on it. This weekend, if I get a chance, I'll measure the current drain when the car is turned off. This is fairly easy to do with a good multimeter.

Once I measure the parasitic drain, I can then easily calculate the rate of battery discharge if the battery's amp-hour rating is available. I will post the findings here.
 
#6 ·
Nice, I’m going to attach my trickle charger (Optimate 4) on it, while I’d prefer not to, it definitely helps my batteries last a longer.

Just need to figure out where to put the quick disconnect where if I forget it, it will detach as I back up.
 
#8 · (Edited)
If the issue is a high parasitic current loss, which is what I believe to be the problem, then a different battery won't help much, if at all, unless it has a significantly higher amp-hour rating than the OEM battery. In most cases with lead-acid batteries, physics dictates that to get a significantly higher amp-hour rating, a physically larger battery is required. This may not be possible fitment wise. And don't be thinking that an expensive Lithium-iron battery is the answer, they're even worse with parasitic loss than lead-acid batteries. However, there may be an ultra-premium lead-acid battery out there with a better amp-hour rating than the OEM. We won't know until we do the research. But simply buying a different battery with the same or similar amp-hour rating is most likely not going to help.

Unless the OEM battery has an unusually high self-discharge rate or is defective, which is doubtful since none are older than a few months, then it's all about the amp-hour rating. So unless the OEM battery has a poor amp-hour rating for its size, again doubtful, a new battery won't help much. Given the same amp-hour rating with the same current draw, virtually any battery will discharge at the same rate.

If you wait until I measure the Ascent's parasitic loss, then I'll also supply a simple discharge rate calculation for how long any battery will last without a recharge based upon its amp-hour rating. Then you can decide if a replacement battery will be worth it.

I plan to measure the Ascent's parasitic current loss this weekend if my business doesn't call me away. But if anyone else who knows how to do this can do it earlier, then that would be great. In fact, the more Ascent owners who can do this the better, because then we'll know for sure the real parasitic current draw based upon more than one Ascent.

See below on how to do it. However, I would add that it's important not to break the battery connection because this may cause the ECM to go into a mode which may draw more current while it resets. You can keep the power alive while you disconnect the primary battery terminals by using a backup battery, then remove the backup battery after the meter is in the circuit.

https://www.youtube.com/watch?v=KF1gijj03_0
 
#9 · (Edited)
I was able to measure the parasitic current drain on my Ascent and I'm happy to report that there does not appear to be a problem. This is good news because if there was a problem here, it would be next to impossible to fix. The Ascent draws only between 15-25ma when powered down, (i.e. no accy, no ignition, doors closed, all lights off). This is well under the 50ma acceptable limit. 15-25ma is not an unreasonable parasitic load on a battery and should not draw down the charge for any reasonable length of time. I could not find the amp-hour rating of the battery so I could not calculate specifically how long it would last with this load, but a battery of the size used in the Ascent is typically around 37 amp-hours. With a parasitic current loss of only 15-25ma, such a battery should last for many weeks before being fully discharged.

That said, the Ascent can still be tough on a battery. As soon as you open the door, the amperage draw goes up to around 4 amps. And since the lights are delayed before they go off after the door is closed, this adds to the drain. Also, when you turn off the ignition, the headlights stay on for a while as well. All of this can add up. I assume the alternator can keep up with the high powered HK amp, the heated seats, the heated mirrors, the rear window defrost, etc., but the battery may not get the best charge when all these high powered accessories are being used.

I used a 500A battery load tester to test the OEM Subaru battery and the results were not great. The battery is rated for 530 CCA, so to test it a 250A load was applied for 15 seconds (the battery was fully charged just before the test). This was repeated three times within 5 minutes. It passed, but just barely. The tester was right on the line between "OK" and "Replace". This is not impressive for a new battery. The battery is manufactured by Johnson Controls. They usually make decent batteries, but Subaru may have specified a cheaper design to save money, who knows.

Considering all of this, I would probably recommend purchasing a better battery if you have issues with the OEM battery going dead or discharging repeatedly. The question is, are better batteries currently available in the size required? I'll dig into that next.
 
#11 ·
I have come to be a fan of Noco products. I too dealt with early battery drain issues and sometimes had rough starts. I bought a 4bank charger and currently hook up my ATVs to it to keep the batteries up to charge. Once every couple months, or before a long trip, I will connect the Ascent to condition the battery and get it back up to charge. It will occasionally read around 50-75% when connected. I have not had any starting issues since. I leave the quick disconnect under the hood but leave the hood slightly propped so I never forget to disconnect. I also keep a Noco genius in the trunk to jump on the go without the need of anyone’s help. It has proven to be a great investment for helping others but I have yet to need it myself. I realize people don’t want to spend money on an item to keep you battery charged, but I look at it more as a maintenance item. I used an optima battery conditioner previously on my other Subaru’s. I’ve always had a slightly higher draw due to my dash cam setups.
 
#12 ·
I’ve been trying to figure it out with this

https://www.jegs.com/Sizecharts/bcigroup.html

Looks like a group 27 might be a good fit to replace our group 35 it has same height and width so our tie down works but1.5” longer on each side. If the terminals are on the right spot I’d give it a shot with a Costco version
 

Attachments

#22 ·
A group 27 battery will have the terminals reversed. Group 27F has the correct terminal locations. Would be nice if it still fits with the extra 3" length. Group 24F is another alternative that may fit better. Either one will be a nice boost in CCA/reserve capacity compared to the OEM though.
 
#14 ·
I had a bad battery but didn't really have issues without a secondary cause. 1. Camping with the hatch open. 2. Listening to the radio on ACC. Or others leaving a light on. Just not turning on the car for two weeks may not be that big a deal. You can always buy a simple battery tester you plug into the car outlet to see the current capacity.
 
#17 ·
Just a FYI, the replacement group 35 battery at Costco is $75. I believe it’s 660 CCA vs the stock 550.

Was gonna get one so I’m not stranded somewhere, but thought it was pretty ridiculous I’m getting a new battery for a 6 month old vehicle. I’ll see if they’ll give me a new one when I bring it in for service after showing them my data (2-3 days it’s under 12v)
 
#18 ·
Just wondering. I’m not up to speed on batteries but there are several types of batteries out there- lead acid, deep cycle, AGM, lithium, etc. if one is upgrading and one wants a bigger power reserve to run an aftermarket sound system and other accessories, what’s the best choice?
 
#21 ·
I guess I'm the lucky one. I've left the car parked at our second home unused for more than a month, some sub-zero nights, 12" of snow on the car when we were next up there, and it started fine.
 
#25 · (Edited)
Battery Replacements

Here is some info on possible battery replacements.

The first place to check for a better battery was CR's Car Battery Ratings. CR does expert and exhaustive tests on automotive batteries, far more than any other source. For Group 35 batteries which is the proper size for the Ascent, the EverStart MAXX-35N (North) came out on top with excellent scores for:

Life
Life test measures how a battery endures repeated charge-and-discharge cycles at hot-climate engine-compartment temperatures. The more cycles endured while maintaining a higher voltage, the higher the score.

Reserve capacity
Reserve capacity estimates how long batteries can run a car if the charging system fails. It also estimates how long the battery will last using lights and accessories with the engine off. This is where the OEM Ascent battery appears especially weak so pay special attention to this rating.

CCA
CCA performance reflects voltage at a load of half the average claimed CCA for each group size after cranking for 15 seconds at 0º F.


The EverStart battery is sold exclusively at Walmart which makes purchasing it convenient for almost everyone. Walmart may sell a lot of lower priced items, but their auto department is actually quite good. The Sears DieHardGold 50835 (North) battery also did well. The EverStart or the Die Hard may work appreciably better than the OEM battery. Both of these batteries are reasonably priced.

Specs for the EverStart MAXX-35N (North):
Model: MAXX-35N
C20 Capacity: 42 Ah
CCA: 640 Amps
Width: 6.90 in
Length: 9.10 in
Height: 8.90 in
Warranty: 36 months

Specs for the Sears DieHardGold 50835 (North)
Model: 50835
Weight: 33.5 lb
C20 Capacity: 37.5 Ah
CCA: 625 Amps
Width: 6.90 in
Length: 9.80 in
Height: 8.90 in
Warranty: 36 months

Here are some other batteries which I trust but were not tested by CR:

NAPA Legend Premium
Model: BAT 8435
Weight: 35.0 lb
C20 Capacity: 39.6 Ah
CCA: 640 Amps
Width: 6.90 in
Length: 9.75 in
Height: 8.88 in
Warranty: 84 months

Bosch High Performance AGM™ Battery
Model: S6
Weight: na
C20 Capacity: 50 Ah
CCA: 680 Amps
Width: na
Length: na
Height: na
Warranty: 48 months

Next, are the super premium batteries. These are considerably more expensive but have excellent specs and purported high performance.

Optima YELLOWTOP® D35
The Optima Yellow Top Absorbent Glass Mat (AGM) batteries are designed to provide excellent starting (CCA) and deep cycling capability (AH reserve capacity). They are expensive at around $255. Optima does not list a battery for the Ascent but they do sell a Group 35 battery which should fit. If you're interested in this battery then try to find a local Optima dealer to ensure the fit in the Ascent. You can order one online, but if it didn't fit it would be expensive to return.

Model: D35
Weight: 36.4 lb
C20 Capacity: 48 Ah
Post Type: SAE Post
CCA: 620 Amps
Width: 6.75 in
Length: 9.38 in
Height: 7.69 in
Warranty: 12 months

Odyssey 35-PC1400T
If you thought the Optima was expensive the Odyssey tops it at around $305, but it has one of the best overall specs I've yet seen for a Group 35 battery. If money is no object then this is one of the best Group 35 batteries you can buy.

Model: 35-PC1400T
Weight: 50 lb
C20 Capacity: 65 Ah
Post Type: SAE Post
CCA: 620 Amps
Width: 6.84 in
Length: 9.46 in
Height: 8.69 in
Warranty: 48 months

Again be careful about the fitment. It's very close to the size of the OEM battery but not exact.

Are the super premium batteries worth 2-3 times the cost of a standard battery? Hard to say, some people swear by them others swear at them. I personally wouldn't spring for one unless I had a very critical use.

So these batteries are some examples of replacements for the OEM battery. I think I'll give the EverStart a shot. I've used EverStarts before and I've generally had good luck with them. When I didn't, Walmart gave me no problem returning them for a full replacement within the warranty period, so be sure to save your receipt. Sears is on the way out so I wouldn't recommend the Die Hard battery, but you may be able to find them on closeout at Sears stores which are closing.

All of these batteries will probably be a superior replacement to the OEM Ascent battery. But before you buy a replacement also consider a Battery Jump Starter. If your OEM battery ever is too weak to start the car, one of these will get you going again. I just picked up a Duracell Powerpack Pro 1100 from Costco for only $89. Not only is it a battery jump starter, but it also has dual 120VAC outlets, dual USB outlets, an air compressor, and an LED light.
 
#26 ·
Thanks for doing the research. I can personally vouch for the Walmart battery. When my Porsche battery died the dealer wanted near $400 for a replacement. I followed the recommendations of the folks over on Rennlist and installed the Ever-Start Maxx. I’ve had no issues with it since and the price was excellent.
 
#27 ·
walmart shows this doesn’t fit the ascent, but I assume their “database” isnt accurate. Autozone also doesnt show any batteries fitting the ascent. How long does it take for these retailers to have accurate info? The Ascent had been out for almost a year...
 
#39 ·
The Odyssey 35-PC1400T arrived about a half hour ago and I’m already done installing. Easy breezy using the VSTM OBD II Vehicle ECU Emergency Power Supply Cable Memory Saver that I connected to my boat battery parked next to the Ascent. It’s a Group 35 size so it fit perfectly with zero mods.

Again, my past experiences with Odyssey batteries have been wonderful. I would rather do it right the first time. If Subaru replaced the battery it would have been with the same problematic one. It’s better to spend a few bucks.

Have a great day everyone.
 

Attachments

#41 · (Edited)
I’m getting my windows tinted tomorrow so I am gong to tell the guys to leave it off the charger (which they normally hook up) when they do the install due to having all the doors open. The battery will be more than fine as I’ve used these before. Amazing batteries. Optima’s use to be pretty good as well but then they sold out years ago their quality went to crap.

I’m expecting the hard starts to be fine if they were battery related which I believe they are. We will find out!
 
#48 ·
#43 ·
Odyssey 35-PC1400T update: had the windows tinted on Wed. Asked the Installers to leave doors open and interior lights on. Tint took a few hours and she fired up immediately. Starts have been quick and strong as expected. It’s overkill, however; I will never worry about battery drain issues again.

I will update if Ireceive another hard start but I expect they were battery related. If you don’t hear back from me on this thread, all is good.
 
#46 ·
Odyssey 35-PC1400T update: had the windows tinted on Wed. Asked the Installers to leave doors open and interior lights on. Tint took a few hours and she fired up immediately. Starts have been quick and strong as expected. It’s overkill, however; I will never worry about battery drain issues again.

I will update if Ireceive another hard start but I expect they were battery related. If you don’t hear back from me on this thread, all is good.
Thanks for all the info on this battery. It's the one I'm looking at having installed. My tailgate needs to be open 4-8 hours on one or two days a week for my dog training. Drive home is an hour. Occasionally, I have several days of workshops where the drive afterwards would be only 15 mins. I've been using a battery disconnect switch each time I train b/c the first time my battery died, the dogs were locked in the back and I was alone in a remote training area. Do you think this battery can handle the 4-8 hrs once or twice a week, or occasionally several days in a row?
 
#44 ·
Does anyone know if leaving the key fob near the vehicle (or inside) will cause measurable additional drain on the car battery? I imagine the car has some sort of RF receiver that remains on all the time to pick up an eventual remote key press, but that's got to be very low drain right? And then there must be a system to sense when the key fob is inside the car vs outside... and I would hope that is low drain as well.

But if people are finding that keeping the key away from the car is good for the car battery (hmm and maybe the key's battery too), I'd like to know that! My car is garaged, and the driveway is gated, so I'm not too worries about theft - and I'm more likely to lose the key in the house than in my car.

F.S.
 
#45 ·
Another update: Yesterday I cleaned my vehicle out extensively since I am getting ready to go on a long road trip. I left all of the doors and rear hatch open while cleaning it out for a few hours, and made sure the interior lights were on. She immediately fired up after the detail with the Odyssey battery as expected.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top