roger23

Which draws less electrical power ? :
-when the car is off and parked, or parked with the alarm/security system armed ?

mobster600

Thread has already been discussed, see below

https://mbworld.org/forums/e-class-w...ndby-mode.html

roger23

That thread doesn't really answer the question :
-if the car is being left for a couple days in a locked garage, regarding the continual electrical power drain, is it better to lock the doors, or leave the car unlocked (no alarm on ) ?

mobster600

Hypothetical- What if for some crazy reason someone broke into your garage and ransacked your unlocked car OR stole the car.....IF that was the best option to provide the best battery life over the couple days......would you be ok with that outcome? I assume the answer would be no. SO wouldnt it be worth the extra battery use IF considering it used more energy (idk if it uses more or less) to provide security to your vehicle?

rbrylaw

+1

bytemaster0

From things that I've observed on my own cars, there is less power draw when the car is locked and alarm is on. Keep in mind the following: 1) When the car is unlocked, it's in standby, and so several systems come on. On the old W212 facelift, that also included the LED headlamp fans, which you could hear. 2) The alarm system draws no more power when armed or disarmed. Its sensing and capabilities are, in part, a byproduct of all other existing systems. Those systems are operative regardless. So, best is to keep it locked, should allow most systems that are in standby to power down, at least for those systems that are able to do so.

threeMBs

Use CTEK (or MB branded) trickle charger - problem solved. I use one for every car in the garage and always leave them unlocked.

cetialpha5

Not a fan of trickle chargers. When they go bad, they can kill the battery. Plus it also cuts into the total charge and discharge cycles you get out of a battery. You're probably better off charging the battery completely before leaving and then giving it another charge afterwards for long term storage. For just a couple of days, I wouldn't even bother. Maybe give it a full charge once every couple of months to make sure it stays fully charged.

JTK44

Just my $.02:

I have a 2008 Porsche Boxster which has less than 9,500 miles - needless to say it is not driven often. Even in the summer, it can go 10 days to 2 weeks without being driven and in the winter it is basically in storage and driven once every 30 days.

In the first 18 months of ownership the battery failed and it was replaced under warranty. Within the next 24 months it went bad again - but it was out of warranty. Thereafter, I replaced it with an equivalent battery from Auto Zone and Porsche of America gave me a trickle charge. I have been using the trickle charger ever since. The charger cycles on and off as necessary - when on a LED red light indicates it is charging. The charger keeps the battery fully charged.

The battery is now 5 plus years old and is working properly.

I gave a similar high quality charger to my friend to use when he puts his Porsche 911 into storage for the winter. The battery is now three years old and is working properly.

I have a Generac 20 KW whole house charger. It too has a built in trickle charger. The battery is now four years old and works perfectly.

While your observation that t trickle charge may "cuts into the total charge and discharge cycles you get out of a battery" may be applicable to the lithium ion battery found in a smart phone, it is not applicable to the batteries found in cars.

To the contrary, letting a car battery fully discharge, actually shortens the life of the battery.

The use of a high quality trickle charger, which keeps your battery fully charged, actually lengthens the life of your battery. I highly recommend its use.

bytemaster0

Absolutely. Lead-acid batteries far prefer being left on a charge maintainer.

cetialpha5

It's still true even for lead acid batteries, but the ones in the phones have much less cycles before they go bad. The problem where the trickle charger goes bad is that if it keeps charging it too often, it ends up baking the battery and the water boils out which ends up frying the battery. That's how those trickle chargers fail.

Never suggested fully discharging a battery. Just give it a full charge every few months. AGM batteries don't lose their charge as easily as regular flooded batteries. The popular thing with manufacturers these days is to tweak their algorithm so that they don't fully charge the battery to get better CAFE numbers.

The battery in my 2008 is 11 years old at this point.

JTK44

Not to go completely off topic but what do you mean when you say:

cetialpha5

BMW is well known for it, that their batteries tend to die early. If you don't fully charge the battery, less output from the alternator gets you better gas mileage which is what CAFE is all about. Replacing the battery early isn't part of that calculation. All about using every trick in the book and they're starting to run out of tricks. Lots of people had their batteries last 10-12 years on the W211 platform. On the W212, lots of them seem to die in the 4-6 year range. Part of it could be due to the location back to under the hood or just a worse charging algorithm. Just a guess, it's not like that's a published thing.

Which is why I recommend giving the battery a full charge once in a while. Not sure if you can get the voltage displayed like you could on the previous generation.

JTK44

I have never heard or read about this: Charging a battery to less than full 100% to achieve better CAFE: Is this your opinion or do you know this for a fact? (I never had a battery failure on the 4 BMW's I owned, two 740i's and two 535i's)

For example, if you charge to 90%, (rather than 100%) and then charge again when it reaches 80% to again go to 90% that will be "10 energy units". If on the other hand you charge to 100% and then recharge to 100% when it reaches 80%, then would be 20 energy units - twice as much. But thereafter, by only charging to 90% rather than 100%, you would be charging twice as often, - so the actually time of charge is exactly the same. If the time of charging is the same, there is no energy (CAFE) savings.

Today's modern cars, draw power from the battery when not being used, far more than cars of even 5 years ago and certainly much more than 15 years ago. By not having the batteries fully charged at all times, the life of the battery decreases.

But I must say, and I have driving since 1957 (OMG that is over 60 years) I never had a battery in old car that lasted 5 years never mind 10-12 years as you posted. Batteries back then lasted 3 to 4 years tops. Today's batteries, if properly maintained, i.e., kept fully charged, last much longer.

This is why I recommend using a high quality trickle charger - one that shuts off automatically when the battery is fully charged.

cetialpha5

The fuel economy for CAFE is a specific drive cycle and test. If you don't really charge the battery during the test, then that will give you slightly better fuel economy.

There was an article a while back on how BMW batteries were failing early and dealers were just replacing the batteries while they were in for service without even telling the owners at one point.

The newer batteries are AGM ones that should last longer than regular flooded batteries. Battery life is also a function of the climate you're in, hot climates will bake the battery, they last longer in colder states. I had a regular flooded battery last me about 8 years at one point. I only replaced it because I didn't think it could last much longer, but never actually had it tested, could have lasted longer I suppose.

JTK44

Without beating this horse to death, if what you say is correct, "If you don't really charge the battery during the test, then that will give you slightly better fuel economy." then all BMW would have to do before the CAFE test is charge the battery to 100% - the CAFE test is relatively short and during this test the battery would not need charging!

Would you give us a link to:

1. The article a while back on how BMW batteries were failing early and dealers were just replacing the batteries while they were in for service without even telling the owners at one point.
2. The popular thing with manufacturers these days is to tweak their algorithm so that they don't fully charge the battery to get better CAFE numbers.

If BMW actually uses an algorithm that does not fully charge the battery, which then leads to early failure of the batteries, then we should all be using a trickle charger to keep our batteries fully charged - as a fully charged battery will last longer!

Just again my $.02: I think the opposite is true: modern electrical systems keep our batteries fully charged, which then leads to a longer battery life (of course there are other reasons including temperature, drain and better materials) - much longer than batteries 15 to 20 years ago!

ua549

Batteries on my BMW regularly fail at 18-24 months of service. BMW regional office said that the car needed to be driven at least 10 miles per day to maintain battery health. I average 3 miles per day. My BMW is the only car that has needed a trickle charger to stay alive in the Florida summer when the electrical draw is the highest.

ygmn

What happens is the alternator output Voltage is lowered to 12Vdc during certain periods so battery is not charge and power is enough to run the car.
This saves Fuel as less load on engine.
GM does this too.
Watch a voltmeter on car.
In old days alternator would output 14.2Vdc and gage would stay there - maybe drop when headlights and blower on high would come on.
But today they hover around 12VDC most of the time
his 12Vdc is not enough to actually charge battery so for certain perdiods of time computer allows alteranator to output over 12v to charge battery.

CarFan1

I haven't locked a car while in the garage for nearly 15 years. Now that I've moved and have a 3.5 car garage I leave the fobs on a hook in the garage and occasionally in the car itself. It has nothing to do with battery draw or saving the battery. Purely for convenience. The only time I carry the fob out of the vehicle is when I get out of the car away from my house. Would love it if I could do away with the key altogether.

CarFan1

I've had a similar experience with my Cayman S. After 2 replaced batteries and the associated hassle I purchased a trickle charger and now I've gone 5 years without a problem. I even keep a discreet sized USB charger in the cigarette lighter 24/7 (the cigarette lighter stays active whether the car is on or not.) The trickle charger is your friend.

ua549

With Keyless Go just put the key in your pocket and forget about it. I haven't used my key since the car was new. You should not leave your vehicles keys in a readily accessible place near/in your car. If a car is stolen and the keys are in it the owner may be charged with a crime depending on jurisdiction. Here police are known to walk the streets looking for unlocked cars or those with visible keys. They'll leave a note and sometimes lock the car.

rbrylaw

In addition, if you don't lock your car and you leave your key in or near the car, the key fob battery will need to be replaced far sooner. When you lock your car, you should double tap the lock button (make sure the red light lights for a moment) so the car and fob stop communicating. This will keep the battery in the fob from running down in just a few months.

Cao Black

I'm with you. I haven't locked a car in my garage since before there were key fobs. So far I haven't had to deal with dead batteries even after leaving them unattended (not on trickle charge) for extended periods like 10 to 14 days. Maybe just lucky, but still...

I have used trickle chargers on other vehicles that sit for even longer periods (months) and had no adverse effects that I know of. I would tell the OP to leave his unlocked unless he has security concerns. Modern cars always use some electricity, even when parked, but it doesn't amount to much on a day to day basis. Except for BMW apparently....

78degrees

Some people do actually live in safe places.
I don't care to lock the car, apartment or snowmobiles where I live. However, I even leave the keys in my snowmobiles (but not in the AMG)

mobster600

It depends where you live. Unfortunately people target homes where I live. In neighborhoods by me, there are dozens of cars on driveways and teenagers used to find open car doors and steal things from them. I wouldnt be naive just because the area is safe, if you are leaving for a few days as the OP mentioned, wouldnt you lock up before you left?