Car Battery

[gaz1250]

Ive bought a brand new battery for my car but it has gone flat within days. I jumped started the car and took it for a good run thinking it would charge up. As soon as I turned the car off and tried to start it again the battery was still flat. Could this be the alternator? Or also I managed to get a bit of charge in the battery but once it was connected to the car without starting the engine the battery went flat but if I disconnect the battery from the car it holds the charge. Could this then mean the alternator is fine but theres a wiring fault somewhere flatterning the battery while its sat overnight? HELP

[teash]

I`d definately say its the alternator, plus I don`t think a battery would normally go flat overnight

[NORMANTHEDOG]

check that there are no lights on at night,including boot.

[chadad]

Sounds as though a diode has gone in the rectifier.
Usually caused by disconnecting the battery while the engine is running.
DIODE = a component that only allows current to flow in one direction.
chadad

[gaz1250]

Could you tell me more details about a DIODE where in the car is it located and also if a got it fixed how much would it cost

[chadad]

Hi Gaz, The alternator generates alternating current .
The cars electrical system uses direct current.
the rectifier converts the AC into DC by means of four diodes.
A diode is a type of transistor that only allows the current to flow in one direction. ( into the battery ).
But If one or more of the diodes fail, then the current can flow back out of the battery.
The rectifier/Diodes are part of the alternator, and to check them you would need a voltmeter and the know how to use it.
After all this explanation the fault could lay elsewere.
Maybe the best advice would be to exchange your alternator. But do you know how to remove and refit the damn thing?
Probably best to get it done by an Auto Electrician.
BTW, Did you disconnect the battery while the engine was running? Not a good idea.

[Harveypool]

I had a similar problem once and it turned out that I had the wrong battery for my type of car!! I didn't know there were different types of battery in the first place. If all else fails check that too.

[jacksonjames]

you have a short some where touch all fuses to see if u get a trembling exsperance if so this is it.
also see if it has any problems with ur power steering