Dead Batteries and Extended Parking

A few years ago, I owned a 1980 Mercedes 450SL.  Despite the criticism the R107 platform garners, it was a good car.  It did, however, have one very maddening problem: if allowed to sit more than 2 weeks or so, the battery would drain flat.  In the 3 or 4 years I owned that car, it bricked at least 2 lead acid batteries- which, at more than $100 a pop, were not cheap.  I figured there was some electrical issue with the car, but never had time or inclination to track it down.  After the second battery, the battery either got disconnected if the car was to sit idle for more than a week, or a trickle charger got put on it.

In this weekend's Wall Street Journal (no link - Paywall) Dan Neil wrote a piece about this very issue.  Except, the focus wasn't on 30-year-old Teutonic coupes.  Apparently, just about every new car has this problem.  2017 Mercedes left at an airport for a week?  Call "Triple A".  Ford Expedition?  According to _Ford_, you might get 10 days of grace out of a battery- if it's fresh.  But plan on more like, um, seven.  Toyota is among the most frugal with the joules, claiming a new Toyota can be parked for "2 or 3 weeks" and still have enough charge to re-motivate the ICE.  

I know most people drive their cars every day- but a lot of enthusiasts have weekend or seasonal drivers that are very much be affected by this.  And what about even the average user who - like the Mercedes driver above - leaves on a week long business trip or vacation, only to return to Detroit at 11PM in January and find the electrons all gone?  

My Corvair sits in a garage- sometimes for a month or two at a time, battery connected, no charger- and still has plenty of juice to spin the flat 6 over vigorously.  I understand new cars place infinitely more demands upon essentially the same lead-acid lump wedged into the engine compartment, but at the same time, shouldn't they also have some technology that senses battery SOC (State of Charge) and soft-powers off the vampire draws on the battery as the car sits?  After all, which is preferable: That your car forgot it's learned transmission shift points and engine calibration, and has to run in default mode for a few miles before getting back up to speed, or, you're stranded somewhere at a very inconvenient time with a car that slurped everything out of the battery to reatain those precious power seat position presets?  

Good points, I don't know how average Joes put up with this stuff. My mom's '06? 1-series will drain its battery to the point that it needs a jump start after about 2 weeks. And if you disconnect the battery, you need to either hook up external power to the front jump connectors or crawl into the very back of the trunk through the dropped rear seats to access the battery again! The "vampire" draw on the car is enough that you'll get a big juicy spark at the terminal when you reconnect the battery.

Edit: Oh also the rechargeable keyfob battery (charges when in the car) will completely drain itself within 2 weeks.

Something else to consider: if the battery drains itself to the point where it "bricks", and the car won't take a jump start, the option may be then to flat tow it to a garage.  And a modern car cannot be taken out of gear without a charged battery.  What do you do then?  Drag the car up onto a flatbed?  Maybe put dollies under the drive wheels?

GameboyRMH: Yes, the modern Bimmers and Merc's are notorious for putting the battery in a decidedly inconvenient place to connect/ disconnect.  Maybe the solution is one of those big red racing battery disconnect switches somewhere?  My R107 used to arcy-sparky when you'd connect or disconnect the battery, too.  

volvoclearinghouse said:

GameboyRMH: Yes, the modern Bimmers and Merc's are notorious for putting the battery in a decidedly inconvenient place to connect/ disconnect.  Maybe the solution is one of those big red racing battery disconnect switches somewhere?

That's what I did for my family's early-2000s Pontiac Montana in Ontario, before that the choice was whether to pay a mechanic to disconnect and reconnect the battery, or to pay a shop to install a new battery. I don't think it has high "vampire" draw, but it sits for a whole year sometimes.

I bought some Harbor Freight chargers for $14 and mounted them on the roof of the golf carts we use to move sailplanes around (no engine - no taxi).  The carts are driven very short bursts and the battery never really gets back to 100%.

Could you place one in a window of the garage where the car is stored?  Mount it outside the building and run a wire?

In reply to 914Driver :

These only work if your cigarette lighter is switched on when the car is off.  On many modern cars, this is not the case.  And if the battery isn't readily accesible, then the alligator clips aren't going to do much good.  

I'm not so much thinking of me, but the other people out there who might be non-car folks and having to deal with this issue.  

A set of these that stay connected to the battery will let you put the plug anywhere convenient. Then you don't need to get to the battery every time. 

Forgot about those.  The battery was under all the Tupperware on my BMW bike (23 screws to open) and that pig tail make life much easier!

volvoclearinghouse said:

In reply to 914Driver :

These only work if your cigarette lighter is switched on when the car is off.  On many modern cars, this is not the case.  And if the battery isn't readily accesible, then the alligator clips aren't going to do much good.  

I'm not so much thinking of me, but the other people out there who might be non-car folks and having to deal with this issue.  

And if you have electronic starting (no physical key to rotate a cylinder), plugging in one of these might put you into IG1 (car turned on) state.. That's what happens with my 2007 Rx-8 when I tried to use one.

 I ve been using these from hft. They are a good anti theft if you hide them in the cigarette lighter holes. The red key comes all the way out and looks like nothing was there.

I'm hesitant to put one on the Prius. I hear it firing up the fuel pump before I even get in from the smart key thing it uses

I've been using the solar charger pictured for a few years now in a vehicle that I usedto store for up to 6 months. It  never had a starting issue. Now I did store it outside so the solar batt. maintainer did have plenty of sun. I now have a much newer vehicle that will be stored in the same manner for the winter. The owners manual did state that you should start the vehicle every 2 weeks or so to avoid a flat battery. I will be testing this by letting it sit for at least a month and then longer if the battery charge is kept viable using this solar maintainer. 

I wired up a solar panel for a geologist customer who got tired of flying home to a dead battery in the airport lot every time he was on site for two weeks.  Plug it in, set it on the dash.  Just enough amperage to keep all the normal parasitic draw under control.

914Driver said:

I bought some Harbor Freight chargers for $14 and mounted them on the roof of the golf carts we use to move sailplanes around (no engine - no taxi).  The carts are driven very short bursts and the battery never really gets back to 100%.

Could you place one in a window of the garage where the car is stored?  Mount it outside the building and run a wire?

 

We ran our whole house(lights and DVD player at least) from one of those and 2 batteries when the power company thought I had to pay the previous tenants bill and shut us off for 7 months. Very much worth the minimal investment. 

BMW/MINI has used that technology for a while now.  They call it IBS (Intelligent Battery Sensor) and it's why you have to pay to have the car reprogrammed when you get a new battery.  It has to at least know the battery is new to adjust charging rate, but more importantly it needs to know if the amp hour rating has changed.  That way it knows when to start shutting down non-essential electrical consumers when the charge gets low.

Luckily most Euro cars have aux power outlets that are always hot, so perfect for a solar charger.

The SL600 MB, R124 I believe had a built in solar panel on the dashboard ahead of the instrument cluster. 

FWIW, I have left a 2015 BMW parked for 3 weeks at the airport and it started right up. 

In reply to RevRico :    I thought those chargers only put out 12V.   12v light bulbs ae available but never heard of a 12v dvd player.

iceracer said:

In reply to RevRico :    I thought those chargers only put out 12V.   12v light bulbs ae available but never heard of a 12v dvd player.

Inverter?

Our Prius has sat for a month in subzero temperatures (though plugged in to a block heater the 12v battery wasn't) and it started right back up.

Keyless ignition…engine start-stop…infotainment interfaces…layers of plastic E36 M3 all over the engine bay…automatic only…wrong wheel drive….and now add this to the list of reasons I can’t get excited about buying a new car.

I propose a 28th amendment to the US Constitution…

Congress shall make no law that prohibits the manufacture, distribution, or use of the super sweet 1980 Porsche 911 SC:

Further, all dog fights will be conducted between F-86’s for the good guys and MIG 15’s for the bad guys because they’re super sweet too.

iceracer said:

In reply to RevRico :    I thought those chargers only put out 12V.   12v light bulbs ae available but never heard of a 12v dvd player.

They sold portable ones before they became standard in the headrest of every minivan, sedan, and show car. $40 or $50, had like an 8 inch screen, and a cigarette lighter male plug.  A car battery at full charge would be good for about 3 hours, so 2 movies most nights. 

We did have a little 200 watt inverter, but I don't think we ever used it. 

In reply to Slippery :

portable dvd player? They have 12v ones for the back seat...