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Anonymous Poster #1

Car Battery

10/31/2017 12:46 AM

Is it normal to read a 1.5 A on the car battery circuit when the car is shut down with only the RF lock is on?

What's the best lifespan of a car battery?

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#1

Re: CAR BATTERY

10/31/2017 12:54 AM

Depends on the amp hour rating of the battery.

1.5 amps discharge = 1.5 amp hours. That sounds a little high to me. Look at your battery specs. A single 12 V car bulb will draw about 1 amp. Typical batteries are somewhere around 100-200 amp hours.

Does the car start OK?

The Top 5 Things That Will Drain Your Battery | YourMechanic Advice

Battery life depends on a LOT of factors. General rule of thumb, 3-5 years. Extreme heat will kill them sooner.

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#2

Re: CAR BATTERY

10/31/2017 1:18 AM

No 1.5 amp draw is high as a parasitic load with key off....you should wait about 30 min after the car is shut off to be sure all systems have powered down.....if it's still high you probably have a relay stuck or a short...trace it out...you might try with the engine cold an rf thermometer and search for a hotspot...

https://mechanics.stackexchange.com/questions/3786/how-many-amps-should-my-car-pull-while-it-is-turned-off

Time for parasitic load to kill battery calculator...

https://planetcalc.com/2283/

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#3
In reply to #2

Re: CAR BATTERY

10/31/2017 2:42 AM

Typical amp draw for automotive components...

http://www.hotrod.com/articles/0804rc-electrical-current/

How to test the battery...

How to test the alternator...

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#19
In reply to #2

Re: CAR BATTERY

11/01/2017 8:12 AM

Depending on the year/model, it may take longer than 1/2 an hour for the thing to fully go to sleep. And if you need to have the door open, you may need to pull all the bulbs...

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#4

Re: CAR BATTERY

10/31/2017 4:25 AM

A1) No.

A2) Can be tens of years.

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#5
In reply to #4

Re: CAR BATTERY

10/31/2017 10:41 AM

On the tens of years point, seems they make better batteries in the UK, than here in the States. My battery usually lasts until the day after the 3 year warranty expires.

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#24
In reply to #4

Re: CAR BATTERY

11/01/2017 1:07 PM

Here in the US, a car battery will last between 3-6 years. In the hot southwest, life is shorter due to the heat. I grew up in the midwest, where it rarely got over 100 degrees. Our car battery would last 4-6 years.

Tens of years is a very long time for a car battery, but I don't live where you do.

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#30
In reply to #24

Re: CAR BATTERY

11/01/2017 3:19 PM

Totally true.

Battery life is very dependent on ambient temperature (of the battery).

In Australia, I have had battery retailers say to expect 2 years due to the 40 deg C heat they endure over summer.

Goodness knows why they keep putting them in the engine bay.

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#31
In reply to #30

Re: CAR BATTERY

11/01/2017 3:37 PM

Embedded design and copper costs money.

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#32
In reply to #30

Re: CAR BATTERY

11/01/2017 6:02 PM

A couple of reasons they put the battery in the engine compartment :

1. Shortest distance between two points. By having the battery as close to the starter as possible, manufacturers can use the smallest gauge cable possible to carry the required current.

2. If the battery were placed in say, the trunk or boot, then the cable would need to be of larger gauge as required and the cable would need to be fed through a tunnel for protection. In addition, once the cable is fed through the tunnel, lugs would need to be crimped on each end.

The service department would need to charge more for the cable, to crimp on lugs and to feed the cable through the tunnel.

The home mechanic would need to have expensive crimping tools.

Today you can go to any auto parts store, anywhere in the world and either get a replacement that fits exactly for your car or you can get a universal cable that will work satisfactory that will bolt on without needing any special tools other than a few common wrenches and maybe a screwdriver.

As for the the battery wearing out quickly in extremely hot or cold environments,

In America we say, " that's the cost of doing business " , or " you can't play if you don't pay " .

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#33
In reply to #32

Re: CAR BATTERY

11/01/2017 6:29 PM

A few cars I've owned have the car battery in different locations:

BMW E34 has the battery under the rear seat.

BMW E36 has the battery in the trunk - very hard to pull out!

BMW E32 has the battery under the rear seat.

BMW E90 has the battery in the trunk.

Porsche 911 (996) and Boxster (986) have the battery under the hood (right in front of the windshield and centered (left/right). The motor is behind the passenger compartment.

Jaguar XJ has the battery in the trunk.

Porsche 912 has the battery under the hood in front of the right tire. The motor is out back.

Alfa Romeo Spider has the battery in the trunk.

Here's the explanations I've heard.

1. Weight balance - They want the f/r balance to be as close to 50/50, so they put the heavy battery on the end opposite of the motor.

2. Space - have you ever looked inside the trunk of a 911? There's no place to put a battery. Ditto for the other cars listed above.

3. Heat - the compartment the engine is in gets hot. They put the battery in places that will stay cooler = longer life.

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#6

Re: Car Battery

10/31/2017 10:42 AM

If that drain is continuous, and even if you've got a great big chunky 200Ahr battery (typical capacity is more like 70Ahr), your battery would be dead if the car wasn't used for about 6 days. With 70Ahr, that comes down to 2 days.

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#7

Re: Car Battery

10/31/2017 10:43 AM

It seems 1.5 amps would drain a battery in a week or two. It's definitely too much leakage. Maybe it's something simple like the trunk light not going off when the trunk is shut.

An interesting, off-topic story I heard on Car Talk: A certain car company was having trouble with 1 out of 6 cars arriving at the dealer with a dead battery. It turned out that the trunk light switch was a mercury switch that turned on at a certain angle of the trunk lid. The cars were transported on car trucks that held six cars. The car on the back was facing downward at an angle which turned on the trunk light.

https://www.cartalk.com/content/problem-ford-plant

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#8
In reply to #7

Re: Car Battery

10/31/2017 10:59 AM

I suspect at least one Darwin Award candidate decided to check the trunk (boot) lid light, by climbing in and closing the lid.

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#10
In reply to #8

Re: Car Battery

10/31/2017 1:53 PM

I hope I'm not responsible for that!

I would just set my cell phone up to record video and shut it in there.

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#22
In reply to #8

Re: Car Battery

11/01/2017 11:02 AM

Cars are required to have an inside release in the trunk these days.

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#23
In reply to #22

Re: Car Battery

11/01/2017 12:45 PM

Now that's what I call newer!

..slow day..

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#37
In reply to #22

Re: Car Battery

11/02/2017 9:03 AM

Yes, but if dumb enough to climb in the trunk, and close the lid, what makes anyone think they could or would find the internal release?

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#38
In reply to #37

Re: Car Battery

11/04/2017 1:06 AM

The release glows in the dark. Another reason for the release is if someone is thrown in the trunk - carjack victim.

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#39
In reply to #38

Re: Car Battery

11/04/2017 6:31 AM

One night my car broke down and I was in a remote area with no cell signal so I couldn't call AAA. I slept in the trunk because it was warmer than inside the cabin, in the morning I pulled the release, climbed out, walked a few miles to where I could get a cell signal, called AAA and i was soon on my way again.

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#40
In reply to #38

Re: Car Battery

11/04/2017 3:47 PM

I doubt there is any danger of getting locked in the trunk of my Miata!

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#25
In reply to #8

Re: Car Battery

11/01/2017 1:08 PM

I bet he didn't own a Miata!

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#9

Re: Car Battery

10/31/2017 1:49 PM

Make sure you wait the 30 minutes before testing. Some cars have little cooling fans and condensation pumps that run on for a bit after you shut down. Remember, modern cars have as much computing power as old desktop PCs had 10 years ago, and computers produce heat that must be dissipated. My Ford will pump out the A/C condensation about 5 minutes after parking. Freaked me out the first time I saw that puddle on the ground. I figure it out one day while sitting in the car writing emails after turning it off, I heard the little pump engage and then heard the water dripping out.

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#11

Re: Car Battery

10/31/2017 1:55 PM

Usually I get 4 year batteries, and change them before the warranty expiration...I don't like to wait for them to go bad and leave me having to jump the car....although I do carry a backup battery pack in the trunk....

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#12
In reply to #11

Re: Car Battery

10/31/2017 2:18 PM

I have one also, but leave it at home, for wifey's 6 month Nissan outing. She isn't driving any more (bad shoulder), so I take it out for a spin about twice/year.

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#13
In reply to #11

Re: Car Battery

10/31/2017 2:49 PM

I buy batteries with at least a two or three year free replacement clause. Then I'm pretty sure I'll get more than three of four years out of my battery, even in Arizona. I write the date of purchase on the battery top.

We have AAA premium so if my wife has problems, they'll come and help her. They will replace batteries, on the spot, and they are not overpriced.

I carry jumper cables in my pickup for other people.

I expect that most people who are in tune with their vehicles can tell when it's just not cranking like it should, I can.

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#26
In reply to #11

Re: Car Battery

11/01/2017 1:35 PM

You can also run a load test on the battery to check the condition. I've found running a load test has been a good indicator of battery condition. Foxwell makes a good battery test tool.

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#14

Re: Car Battery

10/31/2017 3:54 PM

The generally accepted max for allowable parasitic drain on a car battery is 50 mA.

Not sure what you mean by "RF lock is on," but I have seen smart keys and transponders cause excessive drain if a spare key is in the car, or the car happens to be parked in an area with a strong enough RF signal at the right freq.

When you test, make sure the keys are far away from the car. lock the car with the hood open and after 30 minutes, measure the current through each fuse in the fuse box. This could be an iterative process because opening and closing circuits could cause your car to 'wake up'. This will help you identify the circuit with the excessive draw.

4-5 years is a good expectation for car battery life in most US climates.

Good luck!

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#15
In reply to #14

Re: Car Battery

10/31/2017 4:59 PM

Too much on new cars that will fail, and leave the motorist stranded. No sale.

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#27
In reply to #14

Re: Car Battery

11/01/2017 1:39 PM

Good analysis. 1.5A is too high for parasitic drain, however the car could be in some sort of shut down mode and the 1.5A is only there for a short time.

I had the same question about "RF lock is on" and I assumed it had to do with the smart key as well.

We don't know what type of car he has, but Honda's have 3-4 year battery lives - the shortest of the manufacturers. Though it's a bit hotter here in So Cal vs other parts of the country.

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#16

Re: Car Battery

10/31/2017 5:10 PM

How to keep neigbor cow from sleeping on hhood?

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#17
In reply to #16

Re: Car Battery

11/01/2017 12:03 AM

1. Switch cars to a Cattle-lack.

2. Mooooove

3. Calf-eine

4. Steak out the area well.

5. Bull-ets (you could just graze them)

6. Using horns cud be the answer.

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#29
In reply to #16

Re: Car Battery

11/01/2017 2:00 PM

Hire some cow wrestlers....

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#36
In reply to #16

Re: Car Battery

11/02/2017 8:59 AM

So that's where Gerty ended up... been missing that old cow.

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#18

Re: Car Battery

11/01/2017 4:13 AM

Check out : priority start . com

Installation in minutes.

No worry about a parasitic drain

No dead battery.

No problem.

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#20

Re: Car Battery

11/01/2017 8:46 AM

A lot of new cars have a light under the hood is it lit? That could be the extra draw.

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#21
In reply to #20

Re: Car Battery

11/01/2017 10:33 AM

Yeah. New cars from the 70's

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#34
In reply to #20

Re: Car Battery

11/02/2017 7:50 AM

Well and then there is that damn light in the fridge. Every time I look in the fridge that light is still on, no one ever turns it out.

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#35
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Re: Car Battery

11/02/2017 8:03 AM
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#28

Re: Car Battery

11/01/2017 1:51 PM

To answer your question.

1. It could be normal, but you'd have to check with the manufacturer. Also, you didn't mention if it's a continuous 1.5A or if it's there only 15 minutes or so after shut down.

2. The best lifespan of a car battery? Depends on your location, is it kept in a cool garage during the summer, etc. Even the type of battery - regular lead acid, AGM, Lithium Ion, etc.

Your term "RF lock is on"; does that mean you've disabled the smart key (locked it out) or did you mean something else?

If you believe your car is drawing 1.5A continuously, my recommendation is to verify that's the case. The easiest way is to let the car sit for 72 hours and then try to start it. If you're drawing 1.5A for 72 hours, your battery will be dead - make sure you have provisions to recharge the battery or jump start it.

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