Am i Charging a car battery correctly?

spud17

Cant see that the top will come off, it is a big varta with sticker acrooss the top

Quite often this sticky label will be covering some sort of cover allowing access to the cells. This is removable and will snap back in.

Forcing a maintenance free battery open could potentially be very dangerous if sulphuric acid splashes all over your face or hands.

I'm not advocating forcing anything.

TBH if it's been charging at 4 amps for 12 hours and is still under 12v then almost certain a new one is required.
IF you do manage to get enough charge to start the car I certainly wouldn't trust it to retain a charge.

Conor_3

Ebenezer_Scrooge wrote: »

Cant see that the top will come off, it is a big varta with sticker acrooss the top

Well you'd better find a way or you may find your battery exploding from the build up of gases.

spakkker

Maintenance free don't have a breather pipe - don't know why.
Why wasn't the car used for a month - was it because the car was a bad starter?
How old is the battery?
What engine are we talking about?- diesel? petrol- what cc's?
Batteries don't last forever - often they start acting wierd just before they die. A scrapyard would have a good battery for a tenner where I live - east yorks - new for diesel -£35? maybe?

spud17

Just had a re-read, if proper maintenance free, then IIRC they should ONLY be charged at a low rate.
Generally referred to as trickle charging.
This is to avoid what Conor refers to in his post, i.e. explosion.
The maintenance free bit implies it is completely sealed thus not requiring any topping-up.

epninety

Some chargers won't even try to charge a completely flat battery, especially if it's a big one. This is because the charger has protection against having a short circuit across it's output, and a flat battery looks a lot like a flat battery.
You say it's now reading 11.27V, what was it when you started? What does it read with the charger turned on?

One trick I've used in this situation is to use jump leads to connect it to a running car, just for a couple of minutes. The high current boost that the battery gets raises it's terminal voltage high enough that the charger doesn't try to protect itself when you reconnect it.

(Of course if you had a spare car and jump leads you'd probably just jump start the car, but that can be very hard on the alternator and the battery, if it's not already junk, so the charger is a better idea.)

shandypants5

Silly Question really...
But you DO have the charging leads connected the RIGHT way around???

countrygirl27

Im trying to charge a 12v car battery using a 12v sealey power products charger. However, when I set it to 12v nothing happens. I assumed I'd done something wrong and switched it to 24v at which point it started making a quiet humming/crackling sound. Alarmed I turned it off and when I removed the crocodile clips there was a small arc of electircity from the positive cap.

Have I done something majorly wrong? Is it supposed to make a crackling sound? Bit scared to go near it now!

Advice please!

totalsolutions

Hey countrygirl27, still there! I like your spirit.
Please only charge at 12volts and RTFM next time. Lead acid have inherent voltage 2v /cell. a six cell lead acid battery then is 12v. Never charged one up to 24v, although you cannot be the first it <might> go higher but doubt it. Can you put a volt meter across it? Dont use it until you know its back to aprrox. 12v. cause it will break all the vehicle lamps/radio and other electronics aa well as the electronic management control stuff, Very expensive repair bill.

wholesaler

Hi
Slightly related. If you have one of those keys with the chip in then ensure key in ignition is not in the on position before removing and replacing battery. Failure to do so can un program the key/ecu partnership. Found this out the har way on a Renault.

epninety

countrygirl27 wrote: »

Im trying to charge a 12v car battery using a 12v sealey power products charger. However, when I set it to 12v nothing happens. I assumed I'd done something wrong and switched it to 24v at which point it started making a quiet humming/crackling sound. Alarmed I turned it off and when I removed the crocodile clips there was a small arc of electircity from the positive cap.

Unless it's a monster sized charger, you won't have harmed the battery with a few seconds at 24V. You may have damaged the charger but it's unlikely. The only sealey 12V/24V charger I found in a brief web search has a front mounted fuse. this might have blown - pull it out and check if there's a strip of metal joining the two terminals, or if it's melted.

When you select 24V, the charger tries to pump a lot of current into the 12V battery (because it thinks its flat). The hum is because the charger is under load trying to charge the battery.

BTW you shouldn't disconnect a battery while it's charging. Either switch off the charger, or unplug it at the wall first. When charging batteries can give off hydrogen, and you don't want to have sparks near that! Not trying to scare you, the risk is *very* low, but it is a risk. Make sure there's decent ventilation as well.