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#1
Old 04-07-2012, 02:58 PM
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How long should I charge my car battery? Need answer fast

Ooops. Left the lights on for a couple of days. Battery is completely dead; no horn, no lights, no nothing.

I have it hooked up to a charger my dad left in the garage but I can't find any info on the charger. Atlas Battery Service, Model PC-9.

It appears to be working; switch set for 12 volts -- little green light comes on and needle on meter moves to 30 amps. I have no idea how to long to set the timer.

Don't see any identifying numbers on the battery. It is original equipment on a Scion Xa.

Cupboard is bare. Got to go to the store sometime today. Help
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#2
Old 04-07-2012, 03:04 PM
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If your charger has a "start" mode, you can attempt to start the engine immediately. If not, I'd try to start it after an hour or so. If you're lucky, and if it does fire, put some miles on it, freeway speeds best. If not, you'll have to charge longer. As to how long...just long enough to start it.

Last edited by SanDiegoTim; 04-07-2012 at 03:04 PM.
#3
Old 04-07-2012, 03:19 PM
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No "start" mode. The only controls are the 6V/12V switch and the timer. Needle on the meter has dropped down from 30 amps to near zero.

So if it will start now it's better to drive it right away than to leave it on the charger for a while? I'd much rather be stranded in the garage than 30 miles from home with a load of groceries.

Last edited by Turble; 04-07-2012 at 03:21 PM.
#4
Old 04-07-2012, 03:23 PM
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If you are not in a position to run it for at least 20-30 minutes, I'd let it charge for at least a couple of hours before taking it out.
#5
Old 04-07-2012, 03:28 PM
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Ok, I'll let it go for a couple hours. Thanks.
#6
Old 04-07-2012, 03:31 PM
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Isn't the ammeter telling you it's charged? I'm assuming the 30 amp measurement meant it was pouring charge into the battery (for want of more accurate terminology) at a very high rate, and now that it is almost completely charged, that has been reduced to a trickle of nearly 0 amps.
#7
Old 04-07-2012, 03:31 PM
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Quote:
Originally Posted by Turble View Post
No "start" mode. The only controls are the 6V/12V switch and the timer. Needle on the meter has dropped down from 30 amps to near zero.

So if it will start now it's better to drive it right away than to leave it on the charger for a while? I'd much rather be stranded in the garage than 30 miles from home with a load of groceries.
if the needle goes down near zero then it has a the charge it will get.

don't leave on the charger, does no good and will start to damage it.

drive around the block for 15 minutes.

i have not looked up any specifics on your charger.

Last edited by johnpost; 04-07-2012 at 03:33 PM. Reason: added not knowing about that charger specifics.
#8
Old 04-07-2012, 03:57 PM
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It was so much easier when there was only one answer. My knowledge of cars is very near zero and my knowledge of electronics dates to the time of vacuum tubes.

I thought trickle charging was better for batteries ... but that might not apply to car batteries?

So now I'm confused. Do i leave it on the charger, trickling for an hour or two? (The timer goes up to two hours.) Or do I take off now, driving around aimlessly for half an hour and then risk showing up on Nancy Grace in a police standoff where a crazy old guy is shot down while throwing tomatoes at passersby on a Wegman's parking lot while screaming about damn dopers?

The only reference for this charger I find on the net is one for sale as a collectible for $200. Guess it was made in the 1960s.

Last edited by Turble; 04-07-2012 at 03:58 PM.
#9
Old 04-07-2012, 04:19 PM
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if the is a voltage switch and the meter goes to 30A and it was made in the 1960s then likely it is not a charger with a trickle charge mode.

if the needle started at 30 and came down to zero it indicates the battery took the charge that the charger could provide. to leave it on longer is not good for the battery considering what that charger seems to be.
#10
Old 04-07-2012, 04:21 PM
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I used to trickle charge my 120ah batteries overnight at 2-3 amps. 30 amps is a very high rate (for what i imagine is a car battery) and will probably charge the battery quickly 2 hours or so. The trickle will fill it totally. No need. Start it up and drive it a bit.
#11
Old 04-07-2012, 04:26 PM
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Ok. I'm off. If I don't report back within a couple hours watch for me on Nancy Grace.
#12
Old 04-07-2012, 06:19 PM
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It worked. Thanks all.

PS: Anybody wanna buy an antique collectible battery charger?
#13
Old 04-07-2012, 08:28 PM
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If the battery is good you should trickle charge it overnight. A trickle charge is a very low amp charge and will fully charge the battery. Most chargers these days have a setting for a low amp charge. Chargers also now have a "start" setting and a "fast charge setting". These are higher amp charges that get the job done but won't fully charge the battery. If you want to get the longest life possible from your battery you will trickle charge it about every 6 months. Of course, hardly anybody does that.

If the battery is not good, charging will do little good. You might be able to get it to start the car but you are looking at more trouble in the near future. Get a new battery ASAP.
#14
Old 04-07-2012, 08:43 PM
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Quote:
Originally Posted by Turble View Post
I'd much rather be stranded in the garage than 30 miles from home with a load of groceries.
Where the heck are you located that you have to drive 30 miles for groceries?
#15
Old 04-07-2012, 11:19 PM
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Actually, there is a small grocery store one mile away but they told me I had to drive for half an hour at highway speed. Now, I can't get up to highway speed on local roads so I started figuring if I go six miles north or nine miles south to get on the freeway do I still have to drive another half hour because the store there would only be a couple more miles or should I get on the freeway to the north and drive to the store in the south because by then the local store will be closed but the big Wegman's store (to the south) has a much bigger selection and a good bakery.

So I guess I started off taking things too literally and went stream of consciousness when I got to the part I understood.

And yes, I took the magical mystery tour, went north to get on the freeway and doubled back to go the long way. I told you I don't understand cars. Scored a nice loaf of ciabatta, though, and a chunk of real Parmigiano-Reggiano.
#16
Old 04-08-2012, 09:48 PM
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With that type of charger, the battery is typically fully charged when the amperage reading is about a third of what it read when charging was started. In this case, your charging was done before your first post. Leaving it on the charger longer is counterproductive -- overcharging is harmful to the battery.

Using the alternator to charge the battery (by driving the car) is not wise. It usually doesn't fully charge the battery, and it puts extra stress on the alternator. The alternator is not designed for charging a low battery, rather for topping up and maintaining the charge under normal conditions. Assuming the battery was already charged by the time you drove it, it didn't hurt anything, but you wasted a half hour for no good reason, accomplishing nothing.
#17
Old 04-09-2012, 07:05 AM
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If your battery is of the type where you can still unscrew the caps and get access to the electrolyte, you can test the specific gravity of the acid with a hydrometer to assess whether it is fully charged. If, however, it is of the sealed type that seem to be all too common these days, this will not be possible. Fully charged batteries gas freely as the charging current flows. Overnight used to be my criterion for charging, in the days when I drove a beater that had a ground-continuity problem somewhere.
#18
Old 04-09-2012, 04:51 PM
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30 amp is serious charge, my charger is 6amp for large battery setting,4 for medium 2 amp for small.

dead battery is damaged battery theres little you can do about that, so you can't expect that battery to last as long anymore. but yea at 30 amp i wouldn't let it charge all that long. slow is safe, and generally better for battery longevity, but in a pinch you can fast charge so you can get on with it.

but yea if you have the time, over night on a low setting tends to be the best route.

Last edited by Woodenspoon; 04-09-2012 at 04:52 PM.
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