OT: My car battery died, can I charge it with a 12V supply?

[nirvanas silence]

I'm in a pinch so sorry for the OT post.  No one around to jump my car and I need to be somewhere soon.  I have a benchtop 13.8V power supply from Radio Shack rated at 10A.  Can I connect this to the battery and charge it up?  Any resistors or anything needed?  Any ideas?

[Ed G.]

Now, I'm no expert but I think it would charge it, but not too quickly. I've seen some 'trickle chargers' that keep a slow charge on batteries, and they look no larger than most wall-warts. People keep these hooked up to their boats, RVs or lawn mowers so they keep charged, but not overcharged.
My charger has three settings, I think 2, 6 and 12 amps are the settings. Most wall warts are about 1 amp max.

[j0shua]

Well is slow like hell , you need about  12v - 6A  if you wana charge in about 8 hours, but most of all 12v power supply are 1A or 1.5A ....  that take about a week to charge hehe


cheers

[nirvanas silence]

Well my battery is at 8V right now and the power supply is 10A.

[petemoore]

Should charge kwik enough @ 10amps...DONT Overcharge...
 We got charged for a battery that was then put on the charger by 'dude'...at the gas station [we paid for the battery up front] ...battery was fried...no charge at all. He said "New battery, been on "Start' all morning"...there was 'steam' coming out when I got there and he took it off the charger...hardly any spark when I touched across the terminals, the good battery we drove there on threw huge sparks....anyway these things CAN [but will get damaged[ by overcharging.
 One way to tell if it's charging is look at the voltage of the 'dead' battery, then with the charge current applied [whatever amps that is] and then after a while on the charger what the difference is.
 I think most these car batteries hold about 18V before they get damaged by overcharging.

[niftydog]

Well my battery is at 8V right now

Jebus that's low! That's below the typical cutoff voltage for lead acid... it might be shafted.

Is it a sealed one or do you need to add distilled water to it? If so, chances are it's dry as hell and consequently will be almost entirely dead.

Helpful link

[mikeb]

http://duet.harmony-central.com/forums/showthread.php?s=&threadid=895782

:?

Mike

[Paul Perry (Frostwave)]

8v is certainly a very very bad sign, if your car isn't an early Beetle with a 6v nominal battery!
Personally I'd connect it up anyway & watch to see it doesn't bubble violently (stop if it does).
Might have failed through a cell shorting out (crystalline threads of lead can grow & short out cells).

[RobB]

Your psu is perfect for charging car batteries.  At 13.8V you can’t over charge a healthy battery.  Assuming a capacity of about 50 amp hours it should take around 5 hours to recharge it (in rough terms).  

When lead acid batteries fail usually one of two things happen, a cell will either go short circuit or open circuit.  In the open circuit case it won’t draw current when a charger is connected and also will not supply current when a load is connected.  

In the short circuit case it will draw current and over heat.  Some times a domino effect will occur where the heat will destroy cell after cell loosing 2V of potential at a time.  12, 10, 8, 6, etc

If you’ve had it on charge for 5 hours or more and it’s only presenting  8V at the terminals then you’ve probably lost a couple of cells.

[petemoore]

I think all of these newer batteries are sealed?...the old ones could be cleaned out and new electrolyte put in and get a good bit more mileage that way...IIRC it was alot of messing around, involved baking soda and alot of heavy battery shaking...worked good for a while....not recommended, it's Hazmat's dream, I don't think newer batteries allow the 'refurbishing' process....cleaning the crud off the cell plates, that caused the shorts in the battery.
 ANyway something about hydrogen gas appears, and is Highly Explosive...when Charging or discharging fast ...one of those two..if you're using jumper cables and value your health, when connecting the two conductor jumper cable circuit...complete the circuit [make the last connection] at the battery that IS good, connecting it to the bad or dead battery [actuallly Disconnecting it when the hydrogen gasses have built up as it charged real fast] makes for spectacular explosions and almost always causes severe acid burns.

[MattAnonymous]

Well, if you're in the US and can get to an Advance Auto (Discout Auto) or Autozone, they'll charge it for free.  A good solution that I've found works really well is to make sure that the battery has enough water (as long as the battery has removable caps, take off the caps and fill to the bottom of the little holes).  My battery was presumed dead, but I added water, jumped it, and drove around and it hasn't quit since.  When presumed dead, it registered 9v.  Good Luck.

[guitarhacknoise]

ahhhhhhhh,  the benefits of a manual transmission, jumper cables need not apply.

[vanhansen]

ahhhhhhhh,  the benefits of a manual transmission, jumper cables need not apply.

Yup, find a hill or no hill, a couple buddies to push.  I miss my manual transmission.

[Ge_Whiz]

If there's no good reason for failure - like you left the lights or heated rear screen on without the engine running for hours - chances are the battery is unrecoverable. Modern batteries are like that. It's called 'progress'.

[petemoore]

Kicking the battery just before load testing may knock bubbles off the plates, and get more current to flow...

[guitarhacknoise]

- chances are the battery is unrecoverable. Modern batteries are like that. It's called 'progress'.

:lol:

Kicking the battery just before load testing may knock bubbles off the plates, and get more current to flow...

interesting, I will try to remember that.
been trying to convince my dad to write a book on what I call "grandpa tricks" you know like filling the crankcase with diesel to unstick a lifter, or buffing up your work boots with spent motoroil, DON"T GET ANY ON YER SOLES!
or my favorite one from my old "sconie" days, on nights when its gonna drop way down dere -10 , -30 (F) bring the battery inside the house, NO LECTURES PLEASE, you gotta do what ya............fer cripes sakes!

I've been pushing the Title : "Beater With a Heater vs. The ShitRod Deluxe"

-matthias

Oh, I think you can still get 12v & 16v wet cells, check out the nearest marine supply store, BUT.....I think it best not to tell them its for a car, laws and stuff will vary.

[Hal]

Kicking the battery just before load testing may knock bubbles off the plates, and get more current to flow...

and even if it doesn't fix the battery, it'll take out some frustration :-D :-D