How long to fully charge a battery?

[djwimbledon]

Hi Guys

I havge got my Tuscan started this morning after a full drain on the battery due to a light left on in the boot.......how long do i need to drive it to get the battery fully charged up? I took it for 20 mins this morning and it then wouldnt start again so I am guessing this wasnt long enough!

Hope one of you guys can help....

DJ

[NCE 61]

Sometimes when a battery has totally discharged it can't recover it's full capacity. May be best to disconnect the battery and charge on trickle charger for at least 12 hours.

[chris watton]

NCE 61 said:

Sometimes when a battery has totally discharged it can't recover it's full capacity. May be best to disconnect the battery and charge on trickle charger for at least 12 hours.

yes, you're right, if the battery is fully discharged, not only will it not recover its full capacity, I won't recover at all; this has happened to me, only solution, had to buy another battery! (and an accumate charger!)

[GreenV8S]

It will take a good twelve hours or more of driving (more to allow for time with the lights on, stopping/starting the engine etc) to fully charge a healthy battery. But in twenty minutes it should have picked up enough charge to start the engine. Maybe you have a charging fault. Also may be that the battery has been killed by the deep discharge, it always does some damage but in some cases can be the final straw that kills a battery.

[Mr.Cerbera]

I thought recharge values were determined by the amp/hourage rating of the battery.

If I've ever had a totally flat battery, I disconnect it and mix-charge with 8 hours at a high rate and a further 16 hours on trickle. Only times this hasn't worked was when the plates were clogged with deposits.

Given the general running costs of a Tiv, I would recommend a new battery every autumn and thereby remove all those nagging worries.

PJ

[T66ORA]

In my experience the battery doesn`t last that long on any Tiv, if you have recently bought the car, your history file should tell you when the battery was last changed? Any thing over two years and change it, for £50 it aint worth all the hassleThen change every two years, agree with the autumn

[djwimbledon]

Had a new battery fiutted on Xmas eve! Hence my frustration at possibly having a new one put in!! :-(

[richb]

I recon an a new one every 3 years. Get an Accumate and use it... Once flattened they never recover these days. They don't make em' like they used to!

[philip_cooke]

As I understand it with alternators and batteries, you can't fully charge a flat batttery from an alternator. Here goes the techie bit (might have some of it wrong). When the alternator 'sees' the flat battery, it pushes up the current to charge accordingly. This causes a rise in the voltage which then make the alternator think the battery has more charge that it really does. If the battery is not fully decharged, the alternator works fine - which is why we all have them on our cars. A dynamo, on the other hand, charges by sensing current and not voltage, so you can always charge a flat battery on a car with a dynamo. Best bet is to stick it on a charger overnight and try again 8-16 hours later. The alternator will be able to pick up the battery from this point as long as you're using the car regularly.

Also, if you ever need a jump start - don't disconnect the jump cables straight away. Leave both cars connected for a good 10 mins as it helps to equalise the charge. If you disconnect the leads straight away, the alternator will raise the voltage rapidly which could cause a voltage spike to blow your ECU. If you ever call the AA out for a flat battery, DO NOT tell them you've tried jump starting as they will probably then not touch the car (advice from an AA man about 3 years ago).

Hope all this helps