Charging a discharged battery - never done this before!

shaun_from_Africa

There is one safety related reason for connecting the negative lead to somewhere on the car body or engine rather than directly to the battery terminal.
When a lead acid battery is being charged, it produces hydrogen gas which is extremely flammable and this gas can be vented from the battery for a while after the charging has finished.
You can often get sparks when the first charger clip is removed and if this spark occurs on the battery terminal, there is a remote possibility of the hydrogen igniting.
By having the negative clip away from the battery and removing this clip first, you negate the risk of a spark causing the gas to ignite.

Ectophile

roddydogs said:

What has "diesel" or the engine capacity got to do with the charger?

Bigger engines need bigger batteries to start them.  Diesels have a higher compression than petrol engines, and so also need a bigger battery to turn them over.

So it's a charger for big batteries, rather than little ones.

Edit: Suppose we group car owners into 3 groups:

1. Amateur and professional car mechanics.
2. People who know what make and model of car they drive.
3. People who know that their car is the blue one.

Halfords are catering to the second group.  Asking them how many amp-hours their battery is is liable to result in a blank stare.  Asking them how big the engine is may lead to a better response.

_Jem_

I really recommend getting one of those smart chargers if you plan to use one in the future that way you won't run into any problems. they can be connected all the time, It's definitely been helpful to me during lockdown. 

molerat

Those Halfords battery chargers were aimed at the customer walking in and having an instant guide as to which battery charger they needed to suit the generalisation of their type of vehicle. IIRC they were simply 4, 8 or 11 amp chargers marked as up to 1200cc, up to 1800cc, over 1800cc & diesel and the more expensive fully automatic.

MinuteNoodles

kittykat500 said:

Hi
I've got a Toyota Verso 1300 cc that had the boot left open for a number of days and now there is not a peep out of the engine/lights, etc. so I am surmising that the battery is dead.  I've found a battery charger in my shed that was used on my previous car (I think), a Focus, but it says 'over 1800 cc and Diesel' charger but suitable for all 12v lead acid batteries.  The Toyota has a 12V battery installed.  Is it OK to use this charger?

Don't waste your time. The battery is duff. Once a car battery drops below 11.6V sulphation occurs on the plates inside the battery, meaning crystals form on them which kills it. It may appear to be OK if you charge it and use it regularly but you'll find if you leave it stood for a few days or a week or when we get the first cold nights in winter that you come out to a flat battery again.

Ectophile

But charging it up may be enough to get the car going, so the OP can drive to a local motor factor to buy a new one.

_Jem_

Charge it and see what it's like, I have a 13 year old battery it's great at starting in the winter but doesn't hold its charge for very long max would be two weeks. 

knightstyle

Saying that flattening a car battery will permanently damage it is a bit scaremongering.  My car has is over 7 years old, still has the original battery and I have flattened it several times over the years. It still starts the 2ltr Ford diesel first time and i hope it will last a few years more.
On the other hand the battery on DWs Juke failed after 5 years and I don't think it was ever flattened.

molerat

knightstyle said:

Saying that flattening a car battery will permanently damage it is a bit scaremongering.  My car has is over 7 years old, still has the original battery and I have flattened it several times over the years. It still starts the 2ltr Ford diesel first time and i hope it will last a few years more.
On the other hand the battery on DWs Juke failed after 5 years and I don't think it was ever flattened.

Agreed.  A few years back I was always driving around with a jump starter in the boot as I wasn't using the car much and always flattening the battery over winter.  Never had any problems once I started using the car more after that.

Jumblebumble

Ectophile said:

roddydogs said:

What has "diesel" or the engine capacity got to do with the charger?

Bigger engines need bigger batteries to start them.  Diesels have a higher compression than petrol engines, and so also need a bigger battery to turn them over.

So it's a charger for big batteries, rather than little ones.

Edit: Suppose we group car owners into 3 groups:

1. Amateur and professional car mechanics.
2. People who know what make and model of car they drive.
3. People who know that their car is the blue one.

Halfords are catering to the second group.  Asking them how many amp-hours their battery is is liable to result in a blank stare.  Asking them how big the engine is may lead to a better response.

May i suggest that It would be more accurate to say is a charger for big batteries but would be fine for little batteries as your wording might confuse the unwary.