Hi,

So I have a 1200w sub in the back, some slightly higher w lights and some interior lights, all hooked into a direct line off my battery.

Now I looked up how to check battery level (after I'd charged it overnight) and i was around the 85% mark. So I decided to test my problem then as I knew the battery was charged to a good level.

I played the speakers (v loud) for about 5 minutes, then switched it all off, checked the battery again with voltmeter, 83% ish. However the car will not start after doing this. This engine wont even tick over the dials just click up and down and the car makes an unhealthy fast clicking.

Is this a problem with how many amps my battery puts out? There have been occasions where leaving it a good while between running the speakers and starting the car has allowed it to start.

Do I need a new battery? Have I done something wrong?

Cheers, let me know if you need more info!!

How are you working out your %?


General Rule of thumb
12.6v is 100%
12.3v is 50%
12.1v is like 15%
12v is considered flat

However some cars have started with just 12v

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The problem may not be the battery - but the starter motor potentially

However - pulling high amperage from the battery without any charge from alternator isn't gonna help

Ziggy

Ziggy122 said:

How are you working out your %?


General Rule of thumb
12.6v is 100%
12.3v is 50%
12.1v is like 15%
12v is considered flat

However some cars have started with just 12v

---

The problem may not be the battery - but the starter motor potentially

However - pulling high amperage from the battery without any charge from alternator isn't gonna help

Ziggy

Click to expand...

Same way with the volt readings you just put.

But how come it will start perfectly without using the speakers/lights etc before hand?

bump

Sounds like a faulty battery. I would suggest to let it test and replace whit the correct type if it is indeed faulty

Olliefeltham said:

Same way with the volt readings you just put.

But how come it will start perfectly without using the speakers/lights etc before hand?

Click to expand...

Because putting a big load on the battery discharges it. Your Sub alone could need 100 Amps. If the battery is weak this will deplete it rapidly.
If you are running this type of load you need to make sure that the alternator, battery and other parts of the electrical system are in perfect condition. You would probably need to fit a larer alternator for sustained use.

Robert G8RPI.