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 Post subject: One for the car guys
PostPosted: Jun Wed 19, 2019 3:47 pm 
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So quick battery question that I’m sure has a short answer: I have a deregistered vehicle in my driveway that hasn’t been driven in 9 months. The battery will certainly be well below firing capacity at this point. I suddenly need to move the car (like tomorrow): I could give ‘er a jump but am not going to be able to drive around for a few hours to allow the alternator to top it up (might take more than that at this point.) I do not have a battery charger but DO have a DIY 12V DC supply, built with a transformer I salvaged from...a battery charger! Can I just take the battery out and give it a jolt? How long should this take? I know that a lot of old school battery chargers were nothing more than what I have & the contemporary devices just add some automation, just want to get some best practice advice.

Thanks

CaptQ
Paul

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 Post subject: Re: One for the car guys
PostPosted: Jun Wed 19, 2019 3:54 pm 
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What was the current rating of the charger that transformer came from?

You need to charge at a rate of several amps for at least several hours (preferably longer) if the battery is just partially discharged in order to have any hope of starting the engine. If it's really low, it might take longer than you have unless that power supply is capable of putting out 10 amps or more.

I'd start by measuring the battery voltage before charging it. Also note that if you do get it started, even at idle sitting in the driveway the alternator will probably put out more than your power supply does, so it might bring the battery closer to an acceptable charge faster than you would expect.

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 Post subject: Re: One for the car guys
PostPosted: Jun Wed 19, 2019 4:58 pm 
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If you just need to start the car in order to move it once, I would just jump it using another car (battery). If you want to continue to move the car around over the next few weeks/months , you need to fully charge it, and in order to do that, you need to put it on a charger for at least several hours, perhaps overnight. Several amps as was suggested. Depending on the discharge state of the battery, it could just need "topping off", or if fully discharged, it might take a while. Sometimes I've jumped a dead battery to move a car, but the next day, the battery was too weak to start the car again, although after a good (proper) long-term charge, the battery was fine from that point on.

You could try your DIY 12 volt transformer, but note that to fully charge a battery, you need to charge it with a voltage of at least 13 volts and preferably closer to 14. 12 volts might get you there eventually, but it could take longer. Monitor your DIY supply periodically to make sure it's not overheating.

Another idea is to take the battery to an auto repair shop and see if they'll charge it for you. Even places like a Walmart auto service center might be able to do this for you. Might not be free, though.

-Bryan


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 Post subject: Re: One for the car guys
PostPosted: Jun Wed 19, 2019 10:24 pm 
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Depending on how long that battery has sat unused it might not take a charge at all. That would give you cause to move a battery from another car to the one you want to move.
But first of all determine whether the battery is indeed dead at this time. If the vehicle doesn't put drain on the battery it should still work unless it has too much internal leakage. If you're going to be moving it around on a long term basis buy a battery maintainer and plug it in. That will save the battery if it is still good and it will be ready to run to move it.

When you move it, run the engine at least fifteen to twenty minutes at various RPM's and add a bit of a load for short terms. You do that by putting it in drive, hold the brake pedal with your left foot and add a bit of power with the right foot. That makes the engine work harder. Don't hold it too long because that could harm the transmission.

Best long term sitting isn't good. You should go out and run it up about once a week or at least every two weeks.

Mark D.


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 Post subject: Re: One for the car guys
PostPosted: Jun Wed 19, 2019 10:54 pm 
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The battery has basically had its day so no harm if you do whatever you need. What I have found is that a really flat battery that has a lot of time on it will often not draw many amps when you put a charger on it. But after a few hours, I have seen them start to take more and more charge. That is not to say that it is still good. But it can get you where you need to be. No harm in just putting your home made charger on it for as long as you can.

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 Post subject: Re: One for the car guys
PostPosted: Jun Thu 20, 2019 5:19 am 
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Alternators don't like dead batteries. A dead battery will require 12+ hours on a typical home automotive battery charger to reach full capacity. It will start the engine after 3 or 4 hours on the charger, maybe.


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 Post subject: Re: One for the car guys
PostPosted: Jun Thu 20, 2019 7:01 pm 
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Ted wrote:
Alternators don't like dead batteries
"Alternators don't like dead batteries", indeed. I was helping my sister move a dead Subaru, jumper cables to my Ford Ranger, engine at a fast idle, trying to start, no go, let the truck charge the battery for a while, about the 3rd try, the Subaru sputtered into life.
Next day, my Ranger had the battery idiot light on, dead alternator. :x

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 Post subject: Re: One for the car guys
PostPosted: Jun Thu 20, 2019 8:04 pm 
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Depending on the vehicle, some of the newer charging systems read the battery voltage and won't do anything if it's below a certain number. Battery chargers can be made the same way and not all of them will work with a really low battery.

But a really heavy load like trying to start a car with a nearly dead battery can damage an alternator in the vehicle used to jump start the dead one. I have seen that happen many times. If you are going to do that, you are often better off using a loose battery that's not in a vehicle.

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 Post subject: Re: One for the car guys
PostPosted: Jun Thu 20, 2019 8:47 pm 
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That stuff about the alternator being a wimp is true.... For today's alternators, or most of them. But back in the day those things would more often than not way out live the rest of the car. And if it did fail, they were relatively cheap to replace.
Now? Well, I've taken the chance a lot of time and have been 'lucky' because so far I haven't destroyed an alternator in cars newer than 1995. My biggest worry is my wife's car. It's probably pretty safe because it has to carry the load that all the accessories G.M. could put into that Cadillac STS-4 and I think they made it tough enough to run all that crap all at once. If it can do that, it should be able to charge the battery if she doesn't turn all that crap on. (electric seat warmers and seat back warmers and other similar crap that most cars come with these days and I don't use most of them. I like heated rear windows. But heated windshields? That's what defrost is for!
Mark D.


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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 1:27 pm 
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Along similar lines (I think), I have an 07 Mustang that will kill a battery if you don't run it frequently.
So, the last time that I tried to start it, no-go. I put a 6-Amp charger on it and left it for 24 hours.
It took a long time for the amperage to drop and it continued to "trickle" charge at 2-amps for a few hours.

I agree, if you have the time and are not stuck in a parking lot somewhere, slow, complete charging
is the key. For that matter, if you are giving a jump start, maybe with today's alternators and computers,
sitting for awhile, charging and then shut off the jump vehicle before trying to start may be the key?

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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 2:21 pm 
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Location: 18424 PA
Simple, put a disconnect on one of the battery terminals, they sell them at most auto parts stores.


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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 3:15 pm 
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Don Cavey wrote:
Along similar lines (I think), I have an 07 Mustang that will kill a battery if you don't run it frequently.
So, the last time that I tried to start it, no-go. I put a 6-Amp charger on it and left it for 24 hours.
It took a long time for the amperage to drop and it continued to "trickle" charge at 2-amps for a few hours.



That's a common issue with recent Mustangs and one that no one that I am aware of has successfully diagnosed. Some people hold the theory that it's the radio amplifier killing the battery as it apparently doesn't completely power off when the ignition is turned off unless you manually turn the radio off while the key is still on. Others say it's the alternator itself, still others say it's the computer. We have a 2010 and it's always been iffy whether it will start after even 2-3 days sitting, definitely won't after a week or so, and that's with a new battery. I tried checking for parasitic drains but the results are inconclusive, although you would think that 100ma or so isn't going to kill a battery in 3 days.

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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 3:22 pm 
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n3uvt wrote:
Simple, put a disconnect on one of the battery terminals, they sell them at most auto parts stores.


That works well on older vehicles, so does just disconnecting the battery.

On some newer vehicles it's not a good plan to disconnect the battery and leave it that way because too many things can lose their memory. You have to provide backup power to keep the memory alive even if you are just replacing a bad battery. I have read reports of owners having to have the vehicle towed to a dealer after just an hour of being disconnected, they have to reset something with a computer before it will ever run again.

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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 3:58 pm 
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What can lose the memory besides your radio presets and the transmission learning how you drive, everything else will go to defaults and relearn very quickly. Maybe GM has another scam running to bring money to dealers.


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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 4:52 pm 
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I have a 2000 Cadillac ETC that will sometimes shut off all power as it should, but most of the time something keeps on drawing current. I have torn my hair out (so to speak) trying to find the culprit. Finally I just gave up and installed a heavy duty switch just behind the grill in a manner that I can just shut it off or turn it on without even having to raise the hood.

My next thought is to have a solenoid switch that I can control with just a small switch under the dash to shut all power off or back on. And I might actually do that one of these days if I find the time.
Mark D.


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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 5:25 pm 
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It depends on the specific car make of course, but it's wise to consult the operator's manual before disconnecting the battery in late model vehicles. Luxury cars in particular, may require a trip to the dealership for a "reset", before the AC will work again, or electric windows function. Nice, huh? Even cars that don't need a dealer visit will probably have a specific procedure to follow once the battery is re-connected, be sure to follow this exactly.


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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 6:34 pm 
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Would it be so nice for me to be able to own a car that new!
The newest car my wife and I own is a 2008 Cadillac STS-4 and it doesn't need anything done after the battery is disconnected.
The one thing I really dislike about that car is that if all power is dropped, the doors default to locked. So, if you are in a wreck and a heavy short circuit results, or a necessary cable is cut the passengers are locked in the car. I have inquired to G.M. about this, but they didn't have enough interest to reply.
I put a chipping hammer under the drivers seat so at least she can knock out the window for just in case.

Mark D.


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 Post subject: Re: One for the car guys
PostPosted: Jun Fri 21, 2019 7:15 pm 
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Mr. Detrola wrote:
Don Cavey wrote:
Along similar lines (I think), I have an 07 Mustang that will kill a battery if you don't run it frequently.
So, the last time that I tried to start it, no-go. I put a 6-Amp charger on it and left it for 24 hours.
It took a long time for the amperage to drop and it continued to "trickle" charge at 2-amps for a few hours.



That's a common issue with recent Mustangs and one that no one that I am aware of has successfully diagnosed. Some people hold the theory that it's the radio amplifier killing the battery as it apparently doesn't completely power off when the ignition is turned off unless you manually turn the radio off while the key is still on. Others say it's the alternator itself, still others say it's the computer. We have a 2010 and it's always been iffy whether it will start after even 2-3 days sitting, definitely won't after a week or so, and that's with a new battery. I tried checking for parasitic drains but the results are inconclusive, although you would think that 100ma or so isn't going to kill a battery in 3 days.

Thanks for your reply Dennis. The radio is a definite problem. My cousin has an '06 and the CD player died and it sits there and clunks groans and won't spit out the CDs. Then, you get a display "CD ERROR" or something like that. He got another one and it worked for about a year. Then, same problem. My '07 now has the exact same problem. What I wanted to do was pop the fuse for the radio. I have the entire three part dealer service manual. Still couldn't find the specific fuse.

Yes, the radio will play for 10 minutes after shutting off the ignition... until you open a door. I did measure the drain but forget what it was. It does last more than three days, but a month? No way.

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 Post subject: Re: One for the car guys
PostPosted: Jun Sat 22, 2019 2:25 am 
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Well thanks for all the replies-this one got quite a bit of activity for a simple question and glad to see. I took all advice and decided to give the ol' lead pile a good chance at rejuvenation: 12 hours+ on the power supply to top up before attempting a jump. Tested voltage went from an initial 1.4 (getting smoked by a D cell!) to 12.6 so there was serious improvement. In the morning I hooked up the jumpers and gave it a minute before cranking--took a couple of turns but that baby started up! Coughed up a lot of really nasty fumes: yeah, the ol' girl hasn't been run in a while and that gas is pretty old. Well that's why the advice is to keep battery topped up and run the car regularly. :D

Thanks for the advice: I neither blew up a battery nor demolished an alternator and was able to move the vehicle, and that's the critical part. BTW, for all you DIY types (hah) here's the home-brew power supply. The design was nicked from a 50s EICO charger (1060 think), I wanted to assemble this out of 100% spare parts from the junk box and nearly succeeded. I will say that whatever I didn't have already was purchased at steep discount (30A bridge on surplus, 5-way binding posts from a local Radio Shack fire sale.) All wire was either recycled from other projects or reclaimed from my favorite source, dead vacuum cleaners. It's not the prettiest but you can knock it about and it keeps on ticking. I normally use this as an electrolysis supply, at which it performs admirably, but it clearly also has enough oomph to bring a big array back to life.

Thanks to all & happy Friday!

Paul
CaptQ

ps: when the wife and I looked at a new car, all the vehicles had options for heated everything, which sounded really silly. Then we moved into Winter and heated steering wheel sounded like a good idea!


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 Post subject: Re: One for the car guys
PostPosted: Jun Sat 22, 2019 7:21 am 
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n3uvt wrote:
What can lose the memory besides your radio presets and the transmission learning how you drive, everything else will go to defaults and relearn very quickly. Maybe GM has another scam running to bring money to dealers.


It may be a scam, but it's true. Even my 2003 Denali has a half dozen computers that communicate with each other. It goes to the garage about once a year and sometimes comes back with several dozen settings back at the default. I got rid of my Crossfire when it had problems between the computer and a relay board. It took 2 months for the dealer to fix it. When I took it in, I told them it was the relay board. Their factory trained mechanic thought it was the engine computer. I had to send it to Illinois to prove it was OK. They finally believed my diagnosis that the relay board was bad and replaced it. Some vehicles are too complicated these days for a dealer to repair. My wife's solution is to replace her Murano whenever it has a problem. I think we are on number 6.

John


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