I've taken it off the car and connected it to the charger but the amp gauge flicks up to number five on the gauge which is the highest bit, it stays there for a second then flicks down to 0 for a second then back up.

Now last time i used it it didn't do this sooo whats going on now, i'm wondering as the battery is severaly discharged [3v] it's giving max input but to prevent over-heating it's flicking back to zero every couple of seconds? does that sound right?

it's quite a old battery charger and i don't have the instructions

 

Sounds like the charger's knackered to me

 

sounds like the battery has had it to me and thats why its not letting any charge through.

 

it seems to have stabalised now and be stuck on 4 on the gauge, 12.4v is in it now so it must have just been like i said

battery is only a year old so i'm hoping it will recover, we'll soon see though!

 

I've had batteries/chargers do that before., and they've charged up fine.

 

If the battery is quite flat it will draw a lot of current. If your charger is only a small charger (at 5 amps I would think it is a small one) then it won't be able to supply the battery with loads of power and will trip out from time to time to allow itself to cool down. Once it's cooled off it will charge again before tripping it's thermal over load again. this is normal and all battery chargers have the facility. you're just asking too much of it.

A 5 amp charger will charge more (probably double so 10 amps) but they are only rated at a continuous 5 amps before triping thermal overload protection.

 

That battery needs replacing, beyond a certain point the chemical reaction becomes irreversable. So even if it charges to a suitable voltage most of the capacity will have gone.

The lowest it should discharge to depends on the time but anything under 11v will likely suffer.