Modern cars and batteries

[Deschodt]

Serious question, how do you check voltage on a modern car battery ?
My answer: pigtails, apparently... But I'm open to discussion...

I have 2 modern ones at home, with 6 mo old batteries and zero apparent problems, yet both seem to indicate low voltages when checked.

One was showing 12.15 the other 12.35V or so, in the car... In the "old car" world that meant it was toast... However, once out of the car (that sucker is heavy), the battery showed a normal 12.65 ! It seems modern cars have too many doodads and computers sucking volts to give a correct reading... Just open the trunk to access the battery and it's already too late, you've awoken the beast: the computer fires on, the dash probably does its checks, the interior/exterior LEDS come on, mirrors unfold, who knows what else ?

In one case a few months ago I took the battery out and even replaced it pre-emptively based on the voltage - I almost regret it now but it was older - the old battery once sitting in the garage went back up to 12.6V as soon as nothing touched it ! As a side note I'm wondering if that is why batteries seem to live shorter lives these days, lots of draw after shutdown, repeatedly getting to a lower Voltage and higher recharging.

Today I wired in pigtails for a CTEK charger on both, it's weatherproof and will allow me to have the connector exit by the wipers when I plan on recharging with the car sleeping and locked down (otherwise it stays in the engine compartment). Sure enough if I let the cars "sleep" and use this pigtail to check voltage, it appears more normal (takes a *long while* for the cars to go to full sleep though)...

Anyway, wondering if others have similar experiences... Seems you cannot trust voltage across terminals like in an old 911 anymore and get an accurate reading, too much draw already buy the time you get to it, unless maybe you wait for the car to shutdown again...

(and don't get me started on the stupid keyless fobs that will open the car when you touch the handle but never lock it the same way - stuff is getting too high tech to be reliable!)

[KNS]

And a lot of this battery-draining tech we didn’t ask for but it shows up in new cars whether we want it or not.

[manbridge 74]

When you put a new battery in a Panamera you have to code it to the vehicle. The car needs to know the AH rating so the water cooled alternator doesn’t over or under charge it. Tis a bit silly.

[fanaudical]

Water-cooled alternator? AAAAACCCKKK!

[R K T]

I just got rid of a 14 month old 2016 VW....the battery went completely dead and I bought a new battery from autozone. Somehow blew fuses when the new battery was installed and VW voided the warranty because it wasn't a "vw" battery. It was on a Sunday and NO vw parts dept was open at the dealer!

[908/930]

BMW has been using some stupid "Intelligent battery monitor" since at least 2004, and when it fails it drains the battery. Absolutely useless systems that make the cars too complex for the dealers tec's to figure out. The battery also has to be coded to the vehicle, just crap.

They should get there electronics manufactured by Honda or Toyota, at least it would work.

[hardflex]

I've read somewhere that some MBenz cars drain a fully charged battery in 8 days or the like, they can go completely flat in the parking lot of the airport on a long trip. That's just nuts. Also read that 4 or 5 total discharges will kill many batteries on the market.

On some of my 'hobby' cars I actually disconnect the batteries for charging and reconnect when I want to start them, but I've also heard doing that on some of the later cars will cause problems as well. It's just stupidity at work. Who thought that was a good idea.

[Aerkuld]

Funny, I was just thinking about this today. We have two cars in the garage which are about as opposite as one could get from that perspective.

My wife's car is a Ford Fusion Plug-In Hybrid - an amazingly nice car to drive, but so packed full of computer wizardry that it takes a week to go through all the on-screen menus and set up the hundreds of personalized features to where you want them. I was washing it this afternoon with the key in my pocket. It didn't like that. I was close enough for it to sense the key, so whenever the water sprayed on the door handle it would try to unlock the car. As the OP said, unlocking the car means turning on all the interior lights, powering up the dashboard and touch screen, and turning the exterior lights on. My exact thought was "This must be killing the battery"

The other car is the 1964 Morris Mini. In stock form it has a speedometer and a fuel gauge. In it's current form it now has a engine temperature gauge and a tachometer. It has no interior light, and everything else is good old manual toggle switches. Most of the time it sits in the garage with the kill switch off, so the battery isn't even connected.

Cars have come a long way. Sure, they're really nice now and far more reliable, but do we really need all this clutter?

[Bill Douglas]

CTEK knows what's best. Just plug it in and don't worry. they do all that draining full charging stuff and really look after the battery. I hook mine up if I won't be using the car for a week or two.

[john70t]

Hey Motion, why not use this thread as a template and make a "car dumbengineering/hate/omg/petpeeve/whatweretheythinking" website?
Mostly text based for easy overhead.
Have people fill in their own categories.
No responding to others or chit chat.

Have a page with audio feedback buttons "submit your thoughts to the manufacturer".
Choices could be "fu" "arrrgh" "areyastupidboy" and other fine expressions of gratitude.

[pwd72s]

Originally Posted by R K T

I just got rid of a 14 month old 2016 VW....the battery went completely dead and I bought a new battery from autozone. Somehow blew fuses when the new battery was installed and VW voided the warranty because it wasn't a "vw" battery. It was on a Sunday and NO vw parts dept was open at the dealer!

So much for that TV ad showing all the happy hippies at Woodstock then touting how much VW cares about it's customers...

I've noticed the same when measuring voltage at the posts of both the Mustang and Cindy's Camry. Makes the regular use of a battery maintainer almost mandatory in cars not frequently driven.

[enzo1]

OBD2 Memory Saver.....

[R K T]

Originally Posted by pwd72s

So much for that TV ad showing all the happy hippies at Woodstock then touting how much VW cares about it's customers....

Exactly! Company policy added to the attitude of the dealer service manager was TWO strikes you're out.

Still have one vw though......

[pwd72s]

Originally Posted by R K T

Exactly! Company policy added to the attitude of the dealer service manager was TWO strikes you're out.

Still have one vw though......

Somehow, I doubt that one ever drives into a VW dealership service area.

[R K T]

Never!

[onewhippedpuppy]

Don't you have to test modern batteries under load to determine their true life remaining? Almost like a stress test? I know I have heard that simple measurement of voltage at the terminals really doesn't tell you much.

[Deschodt]

Originally Posted by onewhippedpuppy

Don't you have to test modern batteries under load to determine their true life remaining? Almost like a stress test?

I don't know but that makes sense. I do have a load tester but I assume this would require unplugging the battery from the car, it really does stress the battery. In most modern cars the toal unplug that causes a lot more work (reset windows, ECU stuff, my cars anyway)... I like the pigtails idea while the car is asleep... Lazy ;-)

I guess my point was that once you open a door/hood, a modern car is already sucking at the teet and reading are indeed meaningless..

[BlueWing]

My wifes MB 350SLK is a nightmare if the battery drops below 11.5 volts. Car is totally disabled. Happened to her once when we were away for a couple of months.
Doors were dangerous to open due to the weather strip. When the door handle starts to move the windows drop a quarter of an inch to clear the rubber. The ignition plug (key) and steering wheel are locked by a motor as opposed to mechanical means, everything in the car is personalized and attached to each keyholder. Once the voltage drops all is reset including the car thinking it has an automatic tranny.

I don't know of the others but there is also a specific procedure to remove and attached the battery due to so much of the computer controled systems. It is essentially like a rolling PC.

I fortunately found a dealer 45 miles away that was willing to let me buy a battery over the phone and leave it in the showroom for me to pick up that night.

Some kind if silver hydride very specific battery. Battery tender has been installed since then.

I would keep my basic 911SC or My 85 Grumman Kubvan over this one anyday.

Just for the record I had to buy her this car for me to take over her Porsche.

[pwd72s]

Originally Posted by BlueWing

My wifes MB 350SLK is a nightmare if the battery drops below 11.5 volts. Car is totally disabled. Happened to her once when we were away for a couple of months.
Doors were dangerous to open due to the weather strip. When the door handle starts to move the windows drop a quarter of an inch to clear the rubber. The ignition plug (key) and steering wheel are locked by a motor as opposed to mechanical means, everything in the car is personalized and attached to each keyholder. Once the voltage drops all is reset including the car thinking it has an automatic tranny.

I don't know of the others but there is also a specific procedure to remove and attached the battery due to so much of the computer controled systems. It is essentially like a rolling PC.

I fortunately found a dealer 45 miles away that was willing to let me buy a battery over the phone and leave it in the showroom for me to pick up that night.

Some kind if silver hydride very specific battery. Battery tender has been installed since then.

I would keep my basic 911SC or My 85 Grumman Kubvan over this one anyday.

Just for the record I had to buy her this car for me to take over her Porsche.

Does the car have an always live 12V female plug in? Would a fully charged 12V motorcycle battery hooked to a male pug in keep all those memories long enough for a battery change? Not familiar with Mercedes, but a 9v set-up works on my Mustang..

[enzo1]

Originally Posted by pwd72s

keep all those memories long enough for a battery change? Not familiar with Mercedes,

From post #12....OBD2 Memory Saver.....edit:also may be called an Automotive Presets and Computer Memory Saver