Charge a really dead battery, even if it damages the battery.

June 8, 2009 9:32 PM

How can I recharge my nearly-completely-drained car battery so that it will work long enough to drive it to get crushed? I'm hoping to avoid buying a brand new battery just to have it crushed.

My car qualifies for a $1,000 rebate if I crush it, due to some "gross polluter" laws. To qualify, I have to drive it to the crusher under it's own power, and it has to demonstrate that it can start up and run on its own. But I've been letting it sit unused for months. Battery worked before, but now it's dead. I tried jumping it, with the hope that after a 45 minute drive to the dismantlers, it would be charged up enough to start again.

But even revving at 3,000 rpm, I could barely get it to turn over once! And the jumper cables were hot after-wards!

I have to do this on Saturday, or I won't ever get to do it. Is there a tricky way to charge a battery, maybe a way that will ultimately destroy it but will work for a week or two? Can I get some old AC adapter and use it as a trickle charger? How much voltage can I run through it? If I overcharge it overnight, will the battery explode in my room?

posted by brenton to travel & transportation (30 comments total)

I don't know what kinds of cars you're working with here, but I've often revved higher than 3K for a jump. Beyond that, why not do the drive yourself before you need to? 30-60min is fine, and when you get home you can see how well it starts up after you turn it off.
posted by rhizome at 9:39 PM on June 8

I'd suggest avoiding a lot of headache and going out to WalMart or Costco and buying one of those air compressor/battery charger/DC inverter units. You can use that to get the engine turning, at least. They're usually on sale for around $50-60 and might come in handy in other occasions.
posted by Burhanistan at 9:42 PM on June 8

I'd check a junk yard or craigslist for a cheap old battery that works well enough.

If I overcharge it overnight, will the battery explode in my room?

Potentially, yes.
posted by knave at 9:47 PM on June 8

maybe try and find a friend that has a real charger (the sorta big type) and use it on the long / deep charge cycle over night.

On that note maybe your alternator is not working? Do you hear a whining noise after you jump the car?
posted by Black_Umbrella at 9:48 PM on June 8

Revving a car at 3K RPM for a few minutes does almost nothing to charge it. If the alternator still works, drive it on the highway for 30 minutes or so. If that works, then you can plan to drive it on the highway for 15 minutes before heading to the crusher, so you can be sure it'll turn over when they try to start it.
posted by fatbird at 10:03 PM on June 8

The problem is definitely the battery. It is completely dead. While connected to the other car, it tries really hard to turn over, but doesn't quite make it. Everything worked fine before I stopped using the car. There is no whining noise.

@rhizome: that was the plan, and the reason that I tried to jump it today, a week before I need to take it in to be crushed. However, I can't get the car to start at all, the battery is so dead.

I found a 12v 4 amp AC adapter that I am planning on splicing into a sort of makeshift charger. I'm a little worried that it's going to blow up, since I have no way to test it, but I get the feeling that this battery can take 4 amps all night and still be nearly dead.
posted by brenton at 10:04 PM on June 8

Just to clarify: it was my other car that was revving at 3k--while jumping. Not the car that is getting crushed. The car that is getting crushed would not start.
posted by brenton at 10:06 PM on June 8

found a 12v 4 amp AC adapter that I am planning on splicing into a sort of makeshift charger. I'm a little worried that it's going to blow up, since I have no way to test it, but I get the feeling that this battery can take 4 amps all night and still be nearly dead.

The Car Talk guys say that a 6 amp charger will take all night to charge a car battery, so you may need to give it 36 hours?
posted by Burhanistan at 10:08 PM on June 8

just get a cheapo new battery, which is going to cost much much less than the crushing premium that you'll get for the car. I think based on the car I had junked a couple of years ago, that your battery is terminal (if you pardon the pun).
posted by singingfish at 10:16 PM on June 8

You can probably take the battery to an auto parts store or service center and have them test it for you. They can probably charge it for you for a small fee. This is probably cheaper than buying a charger yourself and safer than charging it in your room, and their charger will likely give it a deeper charge.

If it works, disconnect the battery until Saturday in case you have a drainage somewhere. Start it a few times on Saturday morning to make sure the starter OK.
posted by Yorrick at 10:45 PM on June 8

Check the fluid level in the battery. Even so-called "maintenance free" batteries often have removable caps (though they may be well-hidden or flush with the top). Top up as necessary.

Pull the plugs. Jump it & see if will turn over easier with the plugs out, or if any oil / water spurts out the plugholes (given that it's a junker, you may have leaking gaskets or stem seals letting oil or water into the cylinders & making it hard to turn over).

Beg/borrow a BIG charger. Trickle-charging is fine but, for various reasons both physical & chemical, slamming a high rate of charge into a flat lead-acid battery can often rejuvenate it enough to get a few starts out of it. If you can't get a big charger, try jump-starting it again (put the plugs back in first ;-) - if it starts, run it on the highway for at least an hour at as high revs as you're comfortable with e.g. by keeping it in 1 gear lower than normal.

If you can't get it started by charging or jumping after that, or it won't hold a charge at all, you've got a totally shagged battery or bigger problems.
posted by Pinback at 11:20 PM on June 8

Go get yourself a jump box. ( Google jump.box battery ) So you are not throwing money away as you will use it again. Then drive the car under load. Go find some hills to drive up and then stop and start the engine. You should be fine. If you live anywhere near a marine shop go get them to deep charge the battery if you want to go that way,
posted by stuartmm at 11:21 PM on June 8

If the above tricks don't work, go to Pick-n-pull and get a cheap used battery from the front. They usually have them by the counter where you pay for parts. Either that, or go to Wal-Mart or Sears or Costco and get the cheapest battery they have that fits your car.
posted by zippy at 11:47 PM on June 8

Could you get the new battery and take it out when you leave it at the crusher to treat your existing car to a new battery?

And are you 100% that you don't have a warranty on the battery? Even buying a cheap battery at Wal-Mart you get a pretty substantial battery.
posted by moojoose at 11:59 PM on June 8

Uh, substantial warranty. (God...)
posted by moojoose at 12:00 AM on June 9

I found a 12v 4 amp AC adapter that I am planning on splicing into a sort of makeshift charger.

This probably won't work if it is a true 12.0 volt adapter. Lead-acid batteries won't even begin to charge at less than 2.15 volts per cell or 12.9 volts for a 6-cell auto battery. You really need at least 13.5 volts to do the job over night.

You need to borrow an auto battery charger and leave it hooked up for a day or two. Maybe you can find a local gas station with a repair shop that will charge it over night for a few bucks.
posted by JackFlash at 12:20 AM on June 9

Borrow somebody else's battery for a little while. I'm sure you can find somebody else with the same battery in their car.
posted by jabberjaw at 12:29 AM on June 9

The problem is definitely the battery. It is completely dead. While connected to the other car, it tries really hard to turn over, but doesn't quite make it. [...] my other car that was revving at 3k--while jumping. Not the car that is getting crushed. The car that is getting crushed would not start.

Let me get this clear: When you try to start the car to be crushed, it won't start; and when you try to jump start it from another car (with a good battery and the engine running), the car to be crushed still won't start. Is that right?

Because it's my understanding that being jump-started is a lot like having a good battery - if the car won't start when being jump-started, it also not start with a good battery.
posted by Mike1024 at 12:29 AM on June 9

Mike1024: If the battery is very old and completely discharged, the internal resistance of the bad battery could be enough to keep the car from starting, even while connected to a good battery during a jump start.
posted by knave at 12:48 AM on June 9

on review, try what pinback says, check the fluid levels if possible in the battery. If low (you should not see anything above water level), pour in some bottled water...
posted by Black_Umbrella at 1:05 AM on June 9

If I were you I'd find the vehicle with the oldest working battery I or somebody I knows owns, put it in the junker. Buy a new battery for the good car that'll need one soon anyways.
posted by floam at 2:23 AM on June 9 [1 favorite]

I question the battery premise (it may be a problem too), but if you have a car with a dead battery, you are using another car's battery via jumper cables to start your car. At starting time, your battery is irrelevant.

There should be nothing stopping you from diconnecting the [dead] battery, connecting jumper cables to the battery terminals from another car and starting your car. If it won't start, it's not the battery. It's more likely your starter motor. If it does start, hie thee to the junk yard because once the engine stops, you're dead without another jump.
posted by plinth at 2:51 AM on June 9

The problem is definitely the battery. It is completely dead. While connected to the other car, it tries really hard to turn over, but doesn't quite make it. Everything worked fine before I stopped using the car. There is no whining noise.

Even with a totally dead battery, or no battery at all, a car with a good starter should be able to start when connected to another car.

If you do get the car started, you need to drive it for a half hour or so to finish charging the battery.
posted by delmoi at 4:49 AM on June 9

Even with a totally dead battery, or no battery at all, a car with a good starter should be able to start when connected to another car.

Not necessarily, as noted.

The revs aren't really the issue - 3000 rpm is producing current, yes, but it sounds like teh current drain was huge (hence the leads getting so hot). I imagine they were not really thick enough leads. The thicker the jump leads, the better. I've had cars that get hot leads and won't start on relatively thick looking cables, only to burst into life with heavy welding cable used instead. A better solution for a dead battery is to leave the cars connected and with the good engine running at a fast idle (1200-1500rpm) for 5 minutes or more to at least get enough into the battery to cope with the initial current drop of turning the engine. Just adding more revs doesn't make it any easier to transfer the current.

If this car is worth $1000 to you, just buy a cheap battery charger - they're pennies to get and any bodged up solution is stupid when a proper one is so cheap. Check the fluid level, if you can, and charge the battery for a long period (overnight is fine) and try and start it. If the car doesn't even crank over after that, then it is screwed inside and nothing else will save it. Batteries sometimes die if they are left discharged for long periods - especially if it was cold.

In short, don't bodge, just charge the thing and try again. It may be possible,. however, that the battery is too far gone to allow the car to run, in which case it's borrow a battery or you have to buy a new one.
posted by Brockles at 5:31 AM on June 9

Most national autoparts stores will test your battery for free to tell you if it will even hold a charge. If it has too many dead cells, you will never get enough cranking amps out of it.
posted by wrnealis at 7:40 AM on June 9

Please try jumping the car again, but take your dead battery out of the car. You should hook the jumper cables directly to the leads that were hooked up to the battery before. It should start no problem. If it does not, something else is wrong with your car.
posted by odinsdream at 8:26 AM on June 9

Even with a totally dead battery, or no battery at all, a car with a good starter should be able to start when connected to another car.

This is absolutely positively not the case. if you have a battery in your car, and hook up another car, you get the average of the two. It might work that way if you took the battery out of your car and just used the battery in the other car.

I've had old cars for years and too many times I've been out in the cold and unable to start a car with a jump until after it had charged for 5-10 minutes. When first hooked up, no go.

As to the question, why not take the battery from your good car, use it to take the car there and have a friend give you a ride home, then reinstall the battery in your car again. Call the scrapyard and ask if you can switch the bad battery for the good one after they verify that the car will start. You never know they might be OK with it.
posted by Antidisestablishmentarianist at 8:28 AM on June 9

Nthing checking battery fluid level as well. I have revived two batteries I thought were dead simply by filling up partially drained cells with more distilled water.
posted by MonsieurBon at 12:47 PM on June 9

Nth checking to see if there is a way to check the fluid levels in the battery. And using/borrowing a real charger for it. (they aren't too pricey and could be handy down the line).

really curious about the debate around cars starting, running, being jumped on dead batteries.

i've used the dirty cheap trick of disconnecting the battery cables to diagnosis a bad alternator in the past. and i'm pretty darn sure i've started cars with good alternators without batteries in them. (not idea, since the battery acts as a buffer for the juice, but doable in a pinch).
posted by jeribus at 6:02 PM on June 9

I will take the battery in to be charged by a mechanic. I made sure I found a mechanic that has one of the automatic ones, so it starts out at 300 amps and then as the battery gains a charge it decreases the amps until it is just topping it off at like 1 amp. If that doesn't help then I guess I'll have to buy a new battery.

Thanks for all the ideas!

By the way, I also made a 12V 1 Amp trickle charger out of a random AC adapter that I found. I cut the copper wire out of an old computer power cable, stripped the ends, shoved one inside the little socket and electrical taped the other to the ring, then taped it all up and connected the other ends to the battery (the "tip" or inside is positive, the ring or sheath is ground). I'm hoping it will "prime" the battery for it's real charge tomorrow morning. :) It should be useful in other situations as well. :D
posted by brenton at 9:31 PM on June 9