Charging a car battery

tcawley29

Hi guys,
Trying to charge my car battery as there was a light left on inside which drained it.
Battery charger got battery to 10v.
When I came back instead of it reaching 12v it went down to 6v while charging.
Anyone any ideas on this?
The battery was at 0 when I started as this happened two months ago and I never done anything about it.
Thanks

BabyGM146

Are you sure you had the charger set up correctly? Lots of them have multiple modes, for cars or bikes etc, and this would affect charging voltage.

tcawley29

BabyGM146 wrote: »

Are you sure you had the charger set up correctly? Lots of them have multiple modes, for cars or bikes etc, and this would affect charging voltage.

I think so. Its hard to understand. Had it on 12v boost mode. Is it ossible it overcharged the battery while I was away and ruined it?

tcawley29

Okay so this is a sealed battery. I picked it up there and it sounds like a half full bottle of water.
I assume this is bad?

alta stare

If a car battery gets below around 9 - 10v it usually means it's a gonner. No amount of charging will sort it.

tcawley29

alta stare wrote: »

If a car battery gets below around 9 - 10v it usually means it's a gonner. No amount of charging will sort it.

funny enough I tested it there in the car and it started straight away.
Still concerned that it sounds like a bottle of water when lifted now as it wasnt like that

Renegade Mechanic

tcawley29 wrote: »

I think so. Its hard to understand. Had it on 12v boost mode. Is it ossible it overcharged the battery while I was away and ruined it?

Boost...? As in the thing you switch on, to put a "cranking" current to the battery to start the car, instead of charging it?

Some chargers are labelled differently, but if you left the battery on a cranking current while you were away, that battery is cooked

Cerco

How are you measuring the voltage?
What do you mean when you say it sounds like a bottle of water?
Batteries are silent and no way would 6v start a car designed for 12v battery.

pablo128

If it's starting the car, drive the car for a few days, then have the battery tested. Most tyre centres would be able to test a battery for you. If its ok after a few days, great. If not, it's bolloxed and you need a new one.

Giacomo McGubbin

tcawley29 wrote: »

Hi guys,
Trying to charge my car battery as there was a light left on inside which drained it.
Battery charger got battery to 10v.
When I came back instead of it reaching 12v it went down to 6v while charging.
Anyone any ideas on this?
The battery was at 0 when I started as this happened two months ago and I never done anything about it.
Thanks

The battery is done.

Battery Voltage and State of Charge:

12.66v . . . . . . . . . . 100%
12.45v . . . . . . . . . . 75%
12.24v . . . . . . . . . . 50%
12.06v . . . . . . . . . . 25%
11.89v . . . . . . . . . . 0%

coylemj

You left a lead-acid battery lying flat for two months, it's a goner. They gradually deteriorate when left flat, it's a one-way street. It might just about hold enough of a charge to start the car soon after you connected it to a charger but chances are that it will be flat again in the morning.

tcawley29

coylemj wrote: »

You left a lead-acid battery lying flat for two months, it's a goner. They gradually deteriorate when left flat, it's a one-way street. It might just about hold enough of a charge to start the car soon after you connected it to a charger but chances are that it will be flat again in the morning.

got me from Sligo to Galway and back.
Gonna leave the work van at home this week and use my car and see how I get on.
By sounds like a bottle of water I mean I can hear liquid swishing inside it like that when I pick it up.

Any luck and it'll be grand because everything else seems to have come up millhouse today so hopefully this does too :pac:

Thanks for all the help guys

corglass

Renegade Mechanic wrote: »

tcawley29 wrote: »

I think so. Its hard to understand. Had it on 12v boost mode. Is it ossible it overcharged the battery while I was away and ruined it?

Boost...? As in the thing you switch on, to put a "cranking" current to the battery to start the car, instead of charging it?

Some chargers are labelled differently, but if you left the battery on a cranking current while you were away, that battery is cooked

A device only draws as much current as it needs. Providing extra current capacity won't harm anything, it just means it's available to the device if required.

Voltage is a different matter. Any variation here and you can of course cook a battery. Current... no

Renegade Mechanic

corglass wrote: »

A device only draws as much current as it needs. Providing extra current capacity won't harm anything, it just means it's available to the device if required.

Voltage is a different matter. Any variation here and you can of course cook a battery. Current... no

Not if its a cranking current. On the off chance you need to move the car you're charging, and the battery has some to offer, you can switch on a mode that delivers enough current to crank the vehicle's engine. A hundred amps - enough for most average engines with whatever is in the battery.

Batteries can discharge at that rate for a little while, but absolutely will not sustain a flow that size in the other direction without frying.
Trust me

I think we need clarification on the charger though... Is is a yellow yoke on wheels or is is something less "workshop" duty.

Something smaller/ordinary likely doesn't have that function and the battery might be simply stuffed, or mabye it has a desulphation programme that can restore sulphated batteries.

Giacomo McGubbin

tcawley29 wrote: »

got me from Sligo to Galway and back.
Gonna leave the work van at home this week and use my car and see how I get on.
By sounds like a bottle of water I mean I can hear liquid swishing inside it like that when I pick it up.

Any luck and it'll be grand because everything else seems to have come up millhouse today so hopefully this does too :pac:

Thanks for all the help guys

If your voltage figures are accurate, your battery is toast, if you don't get a new one soon, you're going to need a new alternator as well.

visual

The comment that it sounds like a 1/2 full bottle of water would suggest it's been over charged and evaporated 1/2 the battery acid away.

It could be topped back up with distilled water but it's pointless as nearly all batteries are maintenance free these days plus the cell electro plates have most likely suffered deterioration.

A fully discharged battery needs a slow charge over longer time. Quick charge or boost charge is really suitable for topping up a previous charged battery or a fully charged battery that hasn't been used in a while.


Like others have suggested the battery is toast and won't hold its charge over time. While your driving it might be fine as your car is charging it but if left standing it will discharge and eventually won't have enough power to start car.

New battles aren't that expensive sooner or later it will have to be replaced. It warm now so starting is easier but once temperature drops a duff battery will catch you out.