my car battery keeps going flat even with new one?

Question

can the altenator drain as well as charge, or is this rubbish

Answer 1

Check to make sure the boot light is going out when you shut the boot. Always best to check the simple things first.

Answer 2

if the diode pack in the altenator is o/c battery will drain overnight. as already stated. apparently GMs suffer from this. howeaver this problem also occurs when an electrical welder is used on a vehicle without disconnecting the battery and altenator lead. first sign of this is charge light glowing dimly at night when on main beam. a capactitive device across battery terminals stops code loss.

Answer 3

If it is a new battery then who fitted it without checking readings of battery with and without engine running?



Get a volt meter and with the engine running check the reading on the battery. It should be about 13-14 volts when running and about 12-12.5 volts when engine switched off.



If there is a red warning light switched on when the ignition key is in the off position then the alternator is faulty and needs replaced.



You have the choice of a new unit or a reconditioned unit - I've tried recons but they go after 12 months so if holding onto car for a while then probably worth a extra £20-30 for a new unit.

Answer 4

If the alternator is good, remove the cable to the negative battery post and connect an ammeter which can handle a few amps between the cable and the post. (Engine off) Pull fuses 1 by 1 until the current draw stops. You then know which circuit the problem is in. Rear window heaters, alarms, aftermarket stereos, central locking and radio antenna motors are likely spots for these problems.

Answer 5

the altnernator can't drain - it probably isn't working and therefore not charging the battery. You need to start the engine, use a volt meter tester (about £10 to buy) attach it to the battery terminals - if it reads 12.5 volts or more, the alternator works. Turn the engine off and try again - just to make sure. Anything less than 12.5 volts will indicate a faulty alternator.



Just dictated by my boyfriend!!

Answer 6

Hi,



It is most likely your alternator. Your battery only starts the car, after that the alternator takes over and continuously charges the battery to operate your lights, radio, etc. If your new battery keeps dying, it likely isn't being continuously recharged.



Good luck.

Answer 7

yes if it has a fault.



you might also have a leak to earth somewhere draining the battery slowly - take it in for a check they should find the problem fairly easily.

Answer 8

the alternator charges the battery and if it doesn't work then your battery drains. I would get it checked.

Answer 9

Oh, yeah. Something is certainly draining the battery, and it could be the alternator.

Answer 10

Sure can.

If you have a rectifier go out on it.



A rectifier is basicaly a big diode. It allows electricity to flow one way. If it fails, electricity is allowed to go back thru it to ground whie the engine is off.

Answer 11

you might have a bad earth or a interior light might be staying on

Answer 12

yes it can. i had the same problem and it was my alternator.

Answer 13

i pretty sure you need a new altanator that happened to me too!!