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[Mr Skrunts]

My 3.0 Elite has a totally flat but brand new Vx Go battery, the car hasnt been used for ages and therefore will have to enter via doorlock/key and then jump start it.

How many miles would it take to put enough charge in the battery to

A.  Restart the car under it's own power.

B.  Fully charge the battery.

I would base the recharging speed on a 40 mph drive arround local dual carriageways.

TIA.  

[Andy B]

......
B.  Fully charge the battery. .....

I have read in the past that you're looking at about 200 miles! Also depends whether you have lights, heater fan, heated seats, heated rear screen etc etc. Stick it on charge!      
Quicker & cheaper in the long run.

[Markjay]

In my experience, a battery that is too weak to turn the starter (but not completely flat) will have reasonable charge after around 15 minutes normal drive, i.e. fast urban. Obviously it will charge better if this is done on Motorway, and in daylight and good weather so no need for lights/wipers/demister etc. Hope this helps.

[Ian_D]

If its a new battery, I would think 20-30 mins would be enough to allow the car to start under its own power.

However it all depends on how flat the battery actually is, and what condition its in. My vectra had a flat battery (car had been sat for +6 months), jump started it and left it running for a good 35 mins, and it only just had enough power to lock the central locking! Went back to it a week later, and it was totaly dead again!

[ngrainqey]

i think that battery was dead ian!

[hotel21]

Once its jump started, really needs a fair few miles to get it fully back, and thats without any electrical load such as headlights, heater fans, stero and the like.  No doubt someone will quote electrical sums somewhere along the line, but I would prefer to put it on an overnight trickle charge, if possible....

[Mr Skrunts]

If its a new battery, I would think 20-30 mins would be enough to allow the car to start under its own power.

However it all depends on how flat the battery actually is, and what condition its in. My vectra had a flat battery (car had been sat for +6 months), jump started it and left it running for a good 35 mins, and it only just had enough power to lock the central locking! Went back to it a week later, and it was totaly dead again!

Wont open central locking, so flat enough.

Am actually surprised is has gone flat, will fully charge it, but if it goes flat again, will get the battery and charging system chacked out, if the battery shows any sign of weakness then am off to Vx for a replacement.

Will be checking all the connections as well.

[Mr Skrunts]

Once its jump started, really needs a fair few miles to get it fully back, and thats without any electrical load such as headlights, heater fans, stero and the like.  No doubt someone will quote electrical sums somewhere along the line, but I would prefer to put it on an overnight trickle charge, if possible....

Sadly not.

I was allways of the understanding that the car electrical system would run the car on its own with out the battery connected (this may well have been on older cars , and of course once the car was running.) and in theory does if the battery is flat any way.

Therefore isnt the charging system capable of running the whole car and charging the battery at the same time even with the headlights on.

Just a thought as I know someone will know the proper logic to it all.

TIA.  

[hotel21]

Yup, charging system runs the car once started and the excess output runs the lights and stuff then whats left, recharges the battery...

Therefore running the car with the others loads - lights etc - off, then the more thats there for charging the battery...

[willyboy]

My 3.0v6  has new VX battery on it hasnt been used for about 2 mths , it just let me in the central locking yesterday mind -3*C here all day but nothing else just had it on charge overnight its fully charged now, I reckon they will go flat if not used in 2 mths normally coz the alarm jobby uses it ...so reckon there wont be much wrong with your charging system  IMO

[Lizzie_Zoom]

Once its jump started, really needs a fair few miles to get it fully back, and thats without any electrical load such as headlights, heater fans, stero and the like.  No doubt someone will quote electrical sums somewhere along the line, but I would prefer to put it on an overnight trickle charge, if possible....

Sadly not.

I was allways of the understanding that the car electrical system would run the car on its own with out the battery connected (this may well have been on older cars , and of course once the car was running.) and in theory does if the battery is flat any way.

Therefore isnt the charging system capable of running the whole car and charging the battery at the same time even with the headlights on.

Just a thought as I know someone will know the proper logic to it all.

TIA.  

Yes indeed Skruntie, a battery is in the system to purely restart the engine when stopped, and the alternator is quite efficient enough to keep the engine going with even 'accessory' loads on, but of course the less load there is the greater the amount of power placed in storage within the battery! 8-) 8-) 8-).

[Andy B]

Once its jump started, really needs a fair few miles to get it fully back, and thats without any electrical load such as headlights, heater fans, stero and the like.  No doubt someone will quote electrical sums somewhere along the line, but I would prefer to put it on an overnight trickle charge, if possible....

Sadly not.

I was allways of the understanding that the car electrical system would run the car on its own with out the battery connected (this may well have been on older cars , and of course once the car was running.) and in theory does if the battery is flat any way.

Therefore isnt the charging system capable of running the whole car and charging the battery at the same time even with the headlights on.

Just a thought as I know someone will know the proper logic to it all.

TIA.  

Yes indeed Skruntie, a battery is in the system to purely restart the engine when stopped, and the alternator is quite efficient enough to keep the engine going with even 'accessory' loads on, but of course the less load there is the greater the amount of power placed in storage within the battery! 8-) 8-) 8-).

I think you'll likely opps things up taking the battery off a modern running engine. My understanding is that the alternator needs to be loaded up, and as ECU's require a steady 12 volts rather than the 13.5/14 volts that the alternator kick out. The last car I took the battery off while it was running, was a Cortina.

[Tony H]

You may find that the battery is fubard  . If left in a discharged state for a long period the plates oxidise and prevent the battery accepting a full recharge

[Entwood]

If a battery is completely flat there are 2 major considerations :

1. How long has it been flat ? If a lead-acid is left in an uncharged state for more than a few days the lead start to sulphate, this wrecks a battery PDQ. A "smart" charger that gives higher voltage pulses over a very short time can sometimes fix this, but it is often time to replace the battery

2. A car electrical system has no current control, only voltage control, usualy at around 14 v. The battery "state of charge" forms the resistance that limits the amperage that flows into a battery, the higher the charge, the higher the resistance, so the current flow is reduced. A very discharged battery has a very low internal resistance. This can lead to extremely high current flow through the charging circuit, hopefully fuses will protect the alternator from damage, but there is a risk. The high current flow through the battery can lead to overheating (boiling) of the acid, and/or distortion of the plates. If they touch an internal short forms and the cell dies. This is not recoverable.

For the above reasons it is preferable that a discharged battery is charged "off car" by a dedicated charger. These have internal controls that limit the maximum current to prevent (2), and  "smart" chargers have a chance of fixing (1)

A 60 amp hour battery fully discharged will take about 20 hours at 3 amp rate to recharge. If you let the car charge it up in 2 hours .. you've stuck an average of 30 amps at it !!! The maths is quite simple. But what was the "starting" current flow ... probably much higher  ??

HTH

[Mr Skrunts]

Yup, charging system runs the car once started and the excess output runs the lights and stuff then whats left, recharges the battery...

Therefore running the car with the others loads - lights etc - off, then the more thats there for charging the battery...

Makes sence to me.

Cheers Broocie.