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After experiencing a dead battery as a result the hatch being left open, I have been monitoring battery voltage. The voltage of the battery when rested is today 12.31 V. A fully charged battery in my experience should be in the neighbourhood of 12.8. Would the on board parasitic draw be as much as 0.5 volts ? Perhaps a couple of you could check and report your battery voltage. Thanks.
 

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After experiencing a dead battery as a result the hatch being left open, I have been monitoring battery voltage. The voltage of the battery when rested is today 12.31 V. A fully charged battery in my experience should be in the neighbourhood of 12.8. Would the on board parasitic draw be as much as 0.5 volts ? Perhaps a couple of you could check and report your battery voltage. Thanks.
There's a decent amount going on if you're in your car, especially if you have keyless and more so with the capability for approach lighting. The car is half awake whenever the FOB is there, including pre-booting the head unit, which draws current, turning on various lights, and being in a higher "ready" state.
 

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12.31v is almost exactly what mine has been after parking in my driveway. My battery has 31k mi on it now.
The best way to check your battery’s performance is at an auto parts store (autozone, advance, etc). Theyll be able to tell you if your battery is delivering the appropriate # of CCAs.
You can also check your voltage while running and stopped using the head unit’s ‘secret menu’ (hold home while double pressing the tune knob).
 

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After experiencing a dead battery as a result the hatch being left open, I have been monitoring battery voltage. The voltage of the battery when rested is today 12.31 V. A fully charged battery in my experience should be in the neighbourhood of 12.8. Would the on board parasitic draw be as much as 0.5 volts ? Perhaps a couple of you could check and report your battery voltage. Thanks.
 

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I am getting 12.35 volts car has 12000 miles on it. It's a 2019 subaru ascent, took it to dealership and they blamed the lift gate and changed it under warranty. No change in voltage or drop in voltage after the change out. I already got stranded once and had to jump start from my 10 year old car, what a shame. Also the battery used in this car is discontinued I wonder why. Dealership is not changing the battery though.
 

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After experiencing a dead battery as a result the hatch being left open, I have been monitoring battery voltage. The voltage of the battery when rested is today 12.31 V. A fully charged battery in my experience should be in the neighbourhood of 12.8. Would the on board parasitic draw be as much as 0.5 volts ? Perhaps a couple of you could check and report your battery voltage. Thanks.
 

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After experiencing a dead battery as a result the hatch being left open, I have been monitoring battery voltage. The voltage of the battery when rested is today 12.31 V. A fully charged battery in my experience should be in the neighbourhood of 12.8. Would the on board parasitic draw be as much as 0.5 volts ? Perhaps a couple of you could check and report your battery voltage. Thanks.
Parasitic draw is measured in current (milliamps), not via a voltage drop. Parasitic draw is typically around 20-50 mA, anything over 100 mA is generally considered excessive. If you wish to measure your parasitic draw use this method.

A parasitic draw can eventually cause a voltage drop over time as the battery slowly discharges, but is not measured by one.

The battery voltage can be used to determine the battery charge (provided you have an accurate Voltmeter). Here is a table showing Voltage vs Charge:

4208
 

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Parasitic draw is measured in current (milliamps), not via a voltage drop. Parasitic draw is typically around 20-50 mA, anything over 100 mA is generally considered excessive. If you wish to measure your parasitic draw use this method.

A parasitic draw can eventually cause a voltage drop over time but is not measured by one.

The battery voltage can be used to determine the battery charge (provided you have an accurate Voltmeter). Here is a table showing Voltage vs Charge:

View attachment 4208
Right, but, when you apply a load, the measured voltage drops. When you remove the load, the measured voltage increases. Thus, the table works for a battery in isolation. Especially because the Ascent is quite awake by the time someone walks up with a keyfob or opens a door or goes into the diag screen on the head unit.
 

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Right, but, when you apply a load, the measured voltage drops. When you remove the load, the measured voltage increases. Thus, the table works for a battery in isolation. Especially because the Ascent is quite awake by the time someone walks up with a keyfob or opens a door or goes into the diag screen on the head unit.
Correct, but the point I was trying to make is that parasitic draw can be best accurately and most easily measured by a direct amperage (current) reading, not a voltage drop. Trying to measure or gauge parasitic draw via a perceived voltage drop would be difficult and potentially inaccurate because you would need to account for the internal resistance of the battery which varies by manufacturer, battery type, and even the age of the battery; the ambient temperature of the battery which affects the voltage readings, the current charge on the battery, whether or not there was a surface charge on the battery, the existing load, and the millivolt accuracy of the meter doing the test. Too many variables, far better just to directly measure the amperage.

I didn't want to get too technical because not everyone here understands electrical engineering, lol.
 

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Thanks pro for your comment regarding measuring amperage. The challenge here is not parasitic draw but the overall condition of the battery. The battery is not going over 12.35 even after fully charged and is dropping below 12v within 4 days. This should be unacceptable for a car only 13 months old. Dealership is claiming battery is passing the capacity test and there are no issues. I doubt both.
 

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Thanks pro for your comment regarding measuring amperage. The challenge here is not parasitic draw but the overall condition of the battery. The battery is not going over 12.35 even after fully charged and is dropping below 12v within 4 days. This should be unacceptable for a car only 13 months old. Dealership is claiming battery is passing the capacity test and there are no issues. I doubt both.
Is there another dealership you can take it to for testing? I'd hope they'd do a more extensive test.
 

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Dealership is claiming battery is passing the capacity test and there are no issues. I doubt both.
Advance Auto, Autozone, Oreilly, etc all do a free battery condition check. I'd take it there since you're likely to spend less time waiting for them to test it and you can even watch them the whole time. The Advance Auto Parts where I went used a device that prints out a receipt after the test showing you the parameters it measured.
 

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Advance Auto, Autozone, Oreilly, etc all do a free battery condition check. I'd take it there since you're likely to spend less time waiting for them to test it and you can even watch them the whole time. The Advance Auto Parts where I went used a device that prints out a receipt after the test showing you the parameters it measured.
Good point I will try one of the Autostores.
 

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Thanks pro for your comment regarding measuring amperage. The challenge here is not parasitic draw but the overall condition of the battery. The battery is not going over 12.35 even after fully charged and is dropping below 12v within 4 days. This should be unacceptable for a car only 13 months old. Dealership is claiming battery is passing the capacity test and there are no issues. I doubt both.
My recommendation is to purchase an Everstart MAXX 35N battery from Walmart ($99). It's an exact fit for the OEM battery. This battery is highly rated by Consumer Reports and is reasonably priced.

4218


Save the receipt and then contact Subaru Customer Support. They have been reimbursing people for defective or sub-par OEM batteries up to $300 if the dealer won't help. Call them first if you want to be sure they will reimburse you.

This should resolve your problem. I've had no issues since I replaced my OEM battery with the MAXX 35N, even with extended non-use of my Ascent due to the pandemic. The reserve capacity of this battery is far better than the original.
 

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My recommendation is to purchase an Everstart MAXX 35N battery from Walmart ($99). It's an exact fit for the OEM battery. This battery is highly rated by Consumer Reports and is reasonably priced.

View attachment 4218

Save the receipt and then contact Subaru Customer Support. They have been reimbursing people for defective or sub-par OEM batteries up to $300 if the dealer won't help. Call them first if you want to be sure they will reimburse you.

This should resolve your problem. I've had no issues since I replaced my OEM battery with the MAXX 35N, even with extended non-use of my Ascent due to the pandemic. The reserve capacity of this battery is far better than the original.
Thanks pro10is this is great advice and since you have used it successfully it is even better.
 

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I wouldn't worry about the battery. I have an early production 2019 model. What follows is a post I made in December of 2019 on another thread: I would expect a new, fully charged, “12 Volt” low maintenance automotive battery to have an open circuit (no load) voltage of at least 12.6 volts, I’ve seen some noticeably higher. Unfortunately, batteries in modern cars never see a no-load condition due to the need to keep electronics up and maintain some emissions equipment. These parasitic loads can be significant, especially on higher trim levels with more toys. I connected my trusty old Fluke 77 multimeter to the battery and clamped my Fluke 375 meter onto the bundle of wires on the negative terminal of the battery. After sitting for 24 hours at ~46 degrees, my battery voltage was 12.32 volts. As soon as I opened the driver’s door, the voltage dropped to 11.96 volts and continued to drop slowly. During starting the peak load was 233.4 amps and the voltage dropped to 10.18 volts. Once the engine started, the voltage came up to 14.36 on the fluke and my scan guage indicated 14.4 volts. I ran the engine for about five minutes and shut it down. The battery voltage dropped to 12.5 volts almost immediately and then continued to drop slowly. After I turned everything off and locked the car, the draw on the battery was 3.6 amps. By then it was cold and dark and I didn’t want to wait around to see if the load dropped of after a while. I did check the battery voltage on my wife’s 2014 Forester which has a 2 year old Subaru battery in it. It has also been sitting for about 24 hours, the voltage was 12.45 volts. My conclusion is that my battery is OK, not as good as I would expect a new battery to be, but not near death. Based on my readings, and the parasitic load I saw, if I was going to replace the battery, I would look for one with a higher reserve capacity than the stock battery. I’ll also make sure my NOCO Genius Boost HD GB70 2000 Amp 12V UltraSafe Lithium Jump Starter is stashed in the back.

It is now June of 2020 and my OEM battery is still plugging along.
 

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Get one of these off Amazon for about $50. I use it to test my car, boat, trolling motor and fish finder battery. Works with all types of batteries and gives a reasonably accurate measure of a battery's condition. I'm surprised how often I use it. And as you can see in this photo, it was time to replace this battery even though the voltage was good.

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I wouldn't worry about the battery. I have an early production 2019 model. What follows is a post I made in December of 2019 on another thread: I would expect a new, fully charged, “12 Volt” low maintenance automotive battery to have an open circuit (no load) voltage of at least 12.6 volts, I’ve seen some noticeably higher. Unfortunately, batteries in modern cars never see a no-load condition due to the need to keep electronics up and maintain some emissions equipment. These parasitic loads can be significant, especially on higher trim levels with more toys. I connected my trusty old Fluke 77 multimeter to the battery and clamped my Fluke 375 meter onto the bundle of wires on the negative terminal of the battery. After sitting for 24 hours at ~46 degrees, my battery voltage was 12.32 volts. As soon as I opened the driver’s door, the voltage dropped to 11.96 volts and continued to drop slowly. During starting the peak load was 233.4 amps and the voltage dropped to 10.18 volts. Once the engine started, the voltage came up to 14.36 on the fluke and my scan guage indicated 14.4 volts. I ran the engine for about five minutes and shut it down. The battery voltage dropped to 12.5 volts almost immediately and then continued to drop slowly. After I turned everything off and locked the car, the draw on the battery was 3.6 amps. By then it was cold and dark and I didn’t want to wait around to see if the load dropped of after a while. I did check the battery voltage on my wife’s 2014 Forester which has a 2 year old Subaru battery in it. It has also been sitting for about 24 hours, the voltage was 12.45 volts. My conclusion is that my battery is OK, not as good as I would expect a new battery to be, but not near death. Based on my readings, and the parasitic load I saw, if I was going to replace the battery, I would look for one with a higher reserve capacity than the stock battery. I’ll also make sure my NOCO Genius Boost HD GB70 2000 Amp 12V UltraSafe Lithium Jump Starter is stashed in the back.

It is now June of 2020 and my OEM battery is still plugging along.
The OEM battery is simply not a good choice for the Ascent. It has a relatively weak reserve capacity in comparison with other batteries within the same Group 35 size. The Ascent's circuitry puts considerable demands on a battery's reserve capacity. The existing battery just barely keeps up with those demands with little or no reserve. This is too close for comfort in my opinion. In many situations where additional demands can and do occur, it can fail, leaving the user unable to start the vehicle and potentially stranded. In such cases, it would be advisable to replace the battery with one having a superior reserve capacity or at least have a lithium starter battery onboard.

I would not advise anyone to stick with the OEM battery alone without some means of backup.
 
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