Don't disconnect the battery?

[Tom]

I've disconnected bateries on boats, cars and RVs for many years if they were going to sit unused for any length of time. I'd previously disconnected the battery on Chris' rarely used car and, because it was due for a smog check, I hooked up the battery on Friday and drove to the nearest smog test station. Everything passed just fine until the very last test - it does a "check engine light" test - it failed.

The tech explained that, because I'd disconnected the battery, the engine computer lost all the stuff it had learned. The fix? Drive it for 100 miles so the adaptive learning stuff is replaced. Chris is driving the car this weekend, then tomorrow I'll go back to the smog test station.

 

[John From Detroit]

Tom, you might consider putting a smaller (IE: motorcycle) battery in parrallel, use a float charger (one of those 2-4 amp maintainer devices) on it and leave it plugged in, Or use solar depending on where it's parked.

Then disconnect the main battery for storage, and upon return top it off, hook it back up and then unhook the back up battery.

Modern engines need 12-15 vdc all the time

 

[Tom]

Hi John,

I'd recently attached a Battery Minder, but I should have left the battery connected.

 

[woodartist]

I'd be interested in if the engine light goes out after 100 miles. I am paranoid about fire and theft, so if the battery was hooked up maybe some type of small current fuse in line with the battery ( disconnect the main line). Or as John suggested another small capacity battery. ..........Never had the problem or thought about it :

 

[Tom]

I'd be interested in if the engine light goes out after 100 miles.

There's no light on, so there's nothing to go out. The test was apparently a check of information stored in the engine computer and, since it had lost the stored data due to the battery being disconnected, it failed the test. I asked the tech if I'd get any indication in the car that it had regained it's memory, but he said "no, just drive it 100 miles".

I'm also paranoid about fires and was concerned that I might blow out some vehicle electronics with the pulsing that happens with the Battery Minder, so I disconnected the battery for both reasons.

 

[woodartist]

Interesting. I guess if you have a code reader it would show up?

 

[Tom]

Dunno, I don't have a code reader.

 

[woodartist]

Depends on the year of the vehicle but you can one for under $100 at Wal Mart. It helps me in some situations, although the "professional" ones do give better info. AutoZone will read the codes for free...........I've disconnected my batteries for a short time and  didn't see any errors on the reader or dash. Just curious about your situation....always can learn

 

[Tom]

I've disconnected my batteries for a short time and  didn't see any errors on the reader or dash.

I've done it many times, including on this car. I suspect that the reason it hasn't been an issue in the past is because I drove sufficient miles after reconnecting the battery for the adaptive learning to have recorded some data before getting to a smog test station.

 

[Just Lou]

I have and unrelated battery disconnect story.

I had to replace the battery in my '97 Honda Accord some years ago and when I did, and connected the new one, I got a message on the LED display in the radio that said CODE.....  (seems this is an anti theft device feature)  Radio won't work without the code.I consulted the owners manual and was instructed that I needed to enter this 4 or 5 digit code from the sticker supplied with my new owners package.  I'm the second owner so, of course, there is no owners package except for the manual.

I read further in the manual and determined that an alternate procedure (in the event that this sticker with the security code was not available) was to obtain the serial number from the rear of the radio and call my nearest dealer, who could then supply the code.

After staring at the dash for about thirty minutes, I determined that the only way to remove the radio was to;

Remove the ash tray, remove an accessory tray directly above that opening, remove bolts and brackets holding radio, remove radio, flip it over, record serial number.... (about a 45 minute total process with a few bent brackets and broken plastic pieces)

OH yeah!!!!

Now I had to reverse the procedure and make it look good in spite of bent brackets and broken plastic tabs.  (another 45 minute process)

As I was reaching for the ash tray to reinstall it (it was laying on the seat upside down) I saw a number written on the bottom that looked familiar.  It suddenly dawned on my gray matter that it was, in fact, the serial number of the radio.  How was I to know? 

More than a little perturbed at what I had just endured to retrieve that number, I prepared to call the dealer with my new found information so I could reactivate my radio.  But wait!!! there's another set of digits on the ashtray bottom.  Could it be?  Yes it was.  It was the actual code it's self.  (4-1-5-5)

I keyed it in and Willy Nelson was singin' On the Road Again.  true story.... 

 

[caltex]

Tom, when I put the battery minder on my car for storage, I didn't even think of possible damage to the cars electronics.  So I left the battery hooked up.  No problems so far, but if someone knows why I shouldn't do that please let me know.

 

[woodartist]

Great story ;D

 

[Just Lou]

Back on topic....

I had my timing belt replaced in the Honda a while back along with an oil change.  I asked the shop to do the emissions inspection before I picked it up and they said (without hesitation) that they couldn't do that because the battery had been disconnected and I would need to drive it for a hundred miles for the computer to retrain and develop a history.  They said this is so people couldn't fool the inspection process by dumping the computer history so their vehicle would pass.  i.e. a check engine light that only comes on every 30 miles or so......

The computer can actually tell the tech how many miles have been driven between resets. (I'm told)

 

[Tom]

Robert,

Since the car was in your garage, I was concerned about the possibility that your garage and house might burn down 

 

[John From Detroit]

The moral is you shojuld all move to Michigan, we did away with the exhaust pipe sniffers some years ago (1995 I think)

 

[2006F350]

Here is something that may solve your delima about disconnecting the battery

http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=40445&CategoryName=&SubCategoryName=

Larry

 

[Tom]

Interesting Larry, thanks. I won't be installing one of those on any of the cars though. I'll either leave the Battery Minder in place with the battery connected, or just disconnect the battery and make sure I drive 100 miles or more before the next smog check is due.

 

[Tom]

.... I didn't even think of possible damage to the cars electronics.

Robert, thinking about it, the battery is one big capacitor which should protect the vehicle electronics. Yours has worked fine.

 

[Clay L]

caltex

Not exactly the same but close; when we are parked for more than a week or so, I connect a Battery Minder to my MH battery.
I have been doing that for about 3 years and it has been connected for as long as 3 months.with no harm to anything .

My MH battery will discharge due to parasitic drains in about 3 weeks if I don't use the Battery Minder

 

[rubysamm]

I believe 100 miles is just a mileage given based on whats called a "drive cycle"  What has to happen is a specific number of stops , idles, a certain amount of miles drive at a specific RPM etc... A "drive cycle" can occur in as little as 30 minutes if done to manufacturers specification.  Since all may be different they default to 100 miles calculating that all of the above requirements "should" happen within 100 miles.  Sorry to get so technical just wanted to "share"