How long to charge Dead Car Battery

  • Automotive
  • Thread starter russ_watters
  • Start date
  • #1
russ_watters
Mentor
20,288
6,869
Just got a jump start due to having left my trunk ajar last night. Battery was pretty dead ~8.5V. Dead enough that we had to let the jumper car charge it for 10 minutes before it would start. So now it is running in my driveway. How long do you think it will need to charge before it will be safe/charged enough to turn off?
 

Answers and Replies

  • #2
Doug Huffman
Gold Member
804
111
As many hours as you can afford. I am informed that the on-board charging will not restore a dead battery to full charge in reasonable time, demonstrated by a ~5 watt load killing the battery. What is the temperature? Here it's about 10F.

All of my vehicles are diesel. Their batteries are fully charged and watered before the temperatures start to drop.
 
  • #3
nsaspook
Science Advisor
1,016
1,533
If you want the battery to last it needs a full charge cycle to move the sulfate complete away from the plates to recover full capacity. Running your car for hours is not the best way to do it. Buy or borrow a good multi-stage battery charger of at least 15A but not too much current or it will warp the plates and let it run full cycle. I have this, it works great: https://www.amazon.com/dp/B000H961YI/?tag=pfamazon01-20
 
Last edited by a moderator:
  • #4
phinds
Science Advisor
Insights Author
Gold Member
16,741
7,430
Just got a jump start due to having left my trunk ajar last night. Battery was pretty dead ~8.5V. Dead enough that we had to let the jumper car charge it for 10 minutes before it would start. So now it is running in my driveway. How long do you think it will need to charge before it will be safe/charged enough to turn off?
Uh ... do you mean the car would not start WHILE the jumper car was providing juice? I've never heard of a battery that dead. If that's the case, I think you may have other problem, although it does sound like you identified the culprit in the battery discharge.

Answer to your question depends on how cold it is out. If not too cold, 1/2 hour should be plenty. If frigidly freezing out, I don't know.
 
  • #5
russ_watters
Mentor
20,288
6,869
It's 30F. I'm going to stop it at half an hour. I'll look into a charger. Tonight I'm going on an hour drive, which should get it as charged as it is going to get on its own. And I'll make sure my jumper battery is charged this time...

[edit] 13.0V after I shut it off. So I think it should be ok for now...
 
  • #6
Borg
Science Advisor
Gold Member
1,889
2,434
It's 30F. I'm going to stop it at half an hour. I'll look into a charger. Tonight I'm going on an hour drive, which should get it as charged as it is going to get on its own. And I'll make sure my jumper battery is charged this time...

[edit] 13.0V after I shut it off. So I think it should be ok for now...
I was going to suggest driving around for a half hour or so. That usually does it for me.
 
  • #7
Doug Huffman
Gold Member
804
111
XRP Series 7-Stage Battery Charger — 12 Volt, Model# 60109
Serves me well.
 
  • #8
nsaspook
Science Advisor
1,016
1,533
XRP Series 7-Stage Battery Charger — 12 Volt, Model# 60109
Serves me well.
Nice charger.
It's very important in cold weather for the battery to get a complete cycle charge to completely reconvert the plate sulfates back to plate oxides. At 8.5 volts some capacity might be lost permanently but most can be recovered with a good charger.

Car charging systems are designed to maintain a good battery not recharge a dead one.
 
  • #9
dlgoff
Science Advisor
Gold Member
3,914
1,865
I'll look into a charger.
This thread could go in the EE forum and since this is a Science Forum ... I have to post this:

clead1.jpg


Image compliments of Battery University.
 
  • Like
Likes Doug Huffman
  • #10
OCR
898
767
If you want the battery to last it needs a full charge cycle to move the sulfate complete away from the plates to recover full capacity. Running your car for hours is not the best way to do it.
Most every thing you need to know about a lead-acid battery ... charging and discharging, sulfation, and freezing, just about every battery failure mode is metioned...

If you do not like Wikipedia[1], then look here...



Always remember[1] ...
Wiki isn't a credible source, since wiki pages can be edited by anyone.
Even by me ...lol
 
  • #11
67
166
Heat really gets to car batteries here in AZ.

It will be interesting to see batteries start to evolve, so to speak, when more and more new cars automatically shut off the engine when the vehicle comes to a stop. Then the engine restarts "instantly" when the driver presses the gas pedal.

The auto industry will also have to improve starter motors to a great degree I presume. There are glass mat batteries and gel batteries now but they cost a lot more, especially gel batteries.

I wonder if we will ever get away from lead acid batteries? Buying lithium ion batteries of that size would require a bank loan.
 
  • #12
6,265
1,280
I have an old battery charger I bought a few years ago at the swap meet for $10. It has served me well the times I've left something on overnight.
 
  • #13
russ_watters
Mentor
20,288
6,869
It got me to Harrisburg, so I'm good for now...
 
  • #14
nsaspook
Science Advisor
1,016
1,533
Most every thing you need to know about a lead-acid battery ... charging and discharging, sulfation, and freezing, just about every battery failure mode is mentioned..l
All good sources of information. As a hobby I design solar energy battery status monitor systems.
That hunk of lead and acid is a lot more complicated than most people think.
 
  • #15
RonL
Gold Member
1,097
215
It will be interesting to see batteries start to evolve,
I wonder if we will ever get away from lead acid batteries? Buying lithium ion batteries of that size would require a bank loan.
Why get away from something so cheap to make? Just make it so that it doesn't fail. (this would be kinda like thinking inside the box:) )
It can be done, just saying...:D
 
  • #16
67
166
Why get away from something so cheap to make? Just make it so that it doesn't fail. (this would be kinda like thinking inside the box:) )
It can be done, just saying...:D
They have to fail or the companies couldn't sell new ones. :D
 
  • #17
nsaspook
Science Advisor
1,016
1,533
I wonder if we will ever get away from lead acid batteries? Buying lithium ion batteries of that size would require a bank loan.
For just starting an ICE engine once every few hours lead acid batteries are hard to beat. They can designed to be extremely robust and tolerant of charging abuse when used as traction batteries in things like fork-lifts where they are run flat everyday and recharged at very high charge rates.
 
  • #18
256bits
Gold Member
3,319
1,361
Dead battery --> half hour on the charger --> car starts. Cold weather needs more time. Bring the battery indoors to warm it up.
( oh. Phinds already said that )
Been there. Done that.
You won't notice it now, but a discharged car battery takes something like 6 months, or so, off its useful life, but since you don't know how long it was going to last anyways you will never reflect back on the time it was discharged.
Sulfication is never fully recovered. Each start of the car discharges the battery a bit. They finally have to be replaced.
 
  • #19
67
166
For just starting an ICE engine once every few hours lead acid batteries are hard to beat. They can designed to be extremely robust and tolerant of charging abuse when used as traction batteries in things like fork-lifts where they are run flat everyday and recharged at very high charge rates.
No doubt about that. But they do have to be maintained. Car batteries used to have cell caps that screwed in and out. It was no problem to add water, or check specific gravity. Now some batteries (maintenance free) don't even have a way to check anything. Others have to have the tops pried off.

We lose water rapidly here in the heat yet even with an oil change most shops don't touch the battery. I have never had a battery make the full warranty period in AZ.
 
  • #20
dlgoff
Science Advisor
Gold Member
3,914
1,865
Car batteries used to have cell caps that screwed in and out.
My first car was a '51 Chevy (~16 yo). Remember the 6 volt batteries? One cold snowy winter night some friend and I were parked out in the country drinking beer in large quantities. When we were ready to leave, the battery wouldn't turn the engine fast enough to start and stopped trying in about 3 seconds. Well ... went out, popped the hood, unscrewed the 3 caps, observed no water, and being drunk and needing to relieve myself, ... Amazing how fast the engine turned over with new hot electrolyte.
 
  • Like
Likes nitsuj
  • #21
nsaspook
Science Advisor
1,016
1,533
My first car was a '51 Chevy (~16 yo). Remember the 6 volt batteries? One cold snowy winter night some friend and I were parked out in the country drinking beer in large quantities. When we were ready to leave, the battery wouldn't turn the engine fast enough to start and stopped trying in about 3 seconds. Well ... went out, popped the hood, unscrewed the 3 caps, observed no water, and being drunk and needing to relieve myself, ... Amazing how fast the engine turned over with new hot electrolyte.
I wonder that the storage capacity is for a lead uric acid battery?
http://www.halfbakery.com/idea/Uric_20acid_20oxidation_20battery
 
  • #23
nsaspook
Science Advisor
1,016
1,533
Lol. I should get some credit for it's discovery. :mad:
Too late, a better battery is made with #2.
 
  • #24
dlgoff
Science Advisor
Gold Member
3,914
1,865
Too late, a better battery is made with #2.
:oldlaugh::oldlaugh::oldlaugh:

So are those the ones you are designing this around?

As a hobby I design solar energy battery status monitor systems.
:devil:
 

Related Threads on How long to charge Dead Car Battery

Replies
12
Views
2K
Replies
7
Views
640
  • Last Post
Replies
11
Views
2K
  • Last Post
Replies
5
Views
5K
Replies
39
Views
2K
  • Last Post
Replies
8
Views
2K
Replies
8
Views
3K
Replies
3
Views
1K
  • Last Post
Replies
3
Views
4K
Replies
28
Views
2K
Top