Car struggles to start after having accessories on for 20 minutes

I have a 2014 Nissan Altima, having an issue where I am parked for a little bit but sitting in the car. The car is off but I will turn the accessories on (radio, interior lights, sometimes exterior lights, A/C, phone charger, etc) for maybe 20 minutes and when I go to start my car again it struggles really hard to turn back on. It is almost as if the battery is turning over and it finally musters up the ability to crank after 3-5 seconds of audible struggling compared to the usual 1 second seamless crank. However, I have a brand new battery not even a year old, and when I went to get my new battery I had them test the rest of the electrical system and was told everything was fine. I am just concerned because of how bad it struggles to turn back on after running accessories for ~20 minutes, when I have been told that cars should be able to run just accessories for hours without issues.

Extra note: My high beam headlights have started occasionally flickering for less than a second. It does not happen often at all and seems to be random, however I am including this anyways in case it could be tied to any other electrical issues.

Thanks

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If the car is off, why turn on the AC?

Tester

I only do sometimes when its really hot the a/c will still blow somewhat cold air with the car off. not as cold as when the car is on but it helps.

Just let the car idle . You will not use enough fuel to worry about and that will solve your draining the battery problem.

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Sometime you can’t.

Tester

The A/C blower motor shouldn’t operate with the ignition in the accessory position, you must have the ignition in the “Run” position. With all these things on, the draw on the battery will be 30 to 40 amps.

This heavy discharging and recharging of the battery is hard on the alternator and battery, you are going to shorten the life of these.

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First, headlights are not “just” accessories. And that “they can run accessories for hours” advice was more true in the old days, before cars had things like 15 inch computer monitors displaying high resolution graphics, etc.

That’s not to say that 20 minutes is a normal amount of run time before the battery starts getting weak, but you didn’t mention the age of your battery. If you’re running the original battery, it’s kind of a miracle the thing starts at all, whether you run accessories or not.

I’d have the battery checked and possibly replaced, and then I’d stop running headlights and the air conditioner (you are not actually running the air conditioner, because the air conditioner requires the engine to be running in order to cool its refrigerant - you are running the fan and in most cases would get better results if you just rolled the windows down) when the engine isn’t on. I’d also check the manual, which will tell you how to temporarily turn the main display off - that’ll help keep the battery happy, and then it’ll turn itself back on when you actually start the car.

I stated in the original post that the battery in the car is not even a year old. Probably about 7 months. Also I do turn the display screen off because I have read it drains the battery pretty quick. I did not know this about the A/C so will probably not be running it anymore while the car is off. Thanks for the info

However the battery will still drain in about 20 minutes even with the big display screen turned off. It is usually when i’m just sitting in the car with the interior lights on because i’m doing something where I need to see

What’s the reserve capacity of that new battery?

https://www.optimabatteries.com/experience/blog/battery-reserve-capacity

Tester

What are your driving habits? If you mainly do short trips, you are already running a deficit in terms of keeping the battery topped up.

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If you had run the battery down, then it often won’t take longer to start again. It’ll just crank for a few seconds and if it doesn’t start by then it’ll be too late and it’ll need a jump.

Does the engine crank noticeably more slowly after 20 minutes of accessory use? If so then your battery really is low. Your new battery could be defective and have a partially shorted cell. This will cause one out of the six cells in the battery to stay mostly discharged. This condition is difficult to detect because one cell being 0.2 Volts lower than normal won’t seem like much when measuring the 12V output, but the output will drop a lot when the battery is put under load… The battery also won’t take much of a charge since the 5 good cells are full. You have to use a hydrometer to measure the electrolyte in each cell to properly discover this condition. If this is the case then warranty replace the battery while you can.

Open the hood, turn the car off, and wait for a minute. Then measure the battery Voltage with a meter:
These numbers are for regular flooded lead acid, with balanced cells.
12.65V - full charge
12.25 - about half
12.05 - quarter
11.80 - mostly dead, may not be enough to start car.
You can see if your battery is dead with these numbers, however if the Voltage is high and it still struggles to start, then that indicates the bad cell condition.

If you frequently use the accessories for 20 minutes with the blower fan on, you’re likely going beyond the 10% discharge that an engine starting battery is designed for. You could get a marine deep cycle battery instead. If you don’t live in a cold climate the reduced cranking amps from a marine battery won’t be an issue.

Idling the car can use 1/2 a gallon per hour. That’s 60 cents at today’s prices for 20 minutes. Do that 150 times and you paid for a new car battery. You can watch the average MPG on a trip computer slowly go down when idling!

The display doesn’t consume much, 3 to 4 amps. Having the ignition on draws up to 20 amps, headlights; more than 10 amps. blower motor; up to 10 amps.

Most of my trips are pretty long considering I live in the rural country and a trip to the nearest grocery store is 20 miles.

Yes, the car cranks noticeably slower when this happens. I will for sure try this. Thanks for the info.

Our car was three years old. Stopped for gas and the wife was using the radio. In that short time the battery was dead and had to call for a jump. New battery took care of it.

2000 to 3000 hours is typical for a car battery. Maybe 2000 is high considering how much electrical load a modern car has. How many hours do you think were on that battery?

Who knows? Car probably had 40,000 miles and you gotta figure an average of maybe 35 MPH, so maybe 1500 hours.

Try cleaning battery cables. Both ends of both cables.

I think you are asking an awful lot of a battery to sit there with the key in the RUN position with various lighting (especially external) on and a cabin fan to boot.

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