900amp Battery Dying On Startup

[Jap_Muscle]

Hey Guys,

Got a bit of a tricky one here.

Everytime i try to start the car the battery loses power. i attached a meter onto the terminals of the battery and basically its at 80% charge. after trying to start the car. it drops to 50%. if i give it another go the battery is completely dead and the car dosnt move.

the strange thing is.....the lights audio all seem to work fine though.

wats going on you think?

[blind_elk]

How old is the battery?

"80% charge" basically means zip - what actual voltage do you have at the battery (static and start)?

[mad082]

sounds like the battery is dead. only solution is to get a new one.

[Jap_Muscle]

Its a optima yellow top D34 BRAND NEW....been sittn in the garage for 1week. been in the car for 2.

Specs: http://www.optimabatteries.com.au/Content/.../D34_082104.pdf

I know the battery isnt dead. fully charged it overnight with a CTEK charger. metered the draw when the car was off and it was sitting at 11volts and it still dosnt start. so i jump start it with another car. i end up driving the car for about 2 hours. as soon as i turn it off and try to start it again. nothing happens again.

im thinking it may have something to do with the alternator not charging the battery? but i was hoping someone could clarify how a car starts exactly? does it purely relies on the battery to start or is it a combo of the alternator and battery.

Edited February 20, 2010 by Jap_Muscle

[jrm]

Who knows how long the 'new' battery was sitting on the shelf. Take it back under warranty and get them to test/replace it?

[mad082]

yeah as above, the battery may have been on the shelf for a year. but either way, if it is dropping charge after 1 start then it is stuffed no matter how old it is.

[blind_elk]

im thinking it may have something to do with the alternator not charging the battery? but i was hoping someone could clarify how a car starts exactly? does it purely relies on the battery to start or is it a combo of the alternator and battery.

The battery starts the car. Then the alternator re-charges the battery. The battery should have 12V (+ a tad) available before you attempt to start the engine.

It is possible your alternator is shagged. Get the engine running, then measure voltage at the battery - it should be around 14V. If it isn't, the alternator is shagged.

If the alternator is still ok, increase engine revs to around 2000, and measure volts at the battery - should still be around 14V. If it is more, the regulator in the alternator is shagged.

[Jap_Muscle]

ill give it a go.

thanks guys