12v battery

[andrey77]

Hi. 

Car stay locked for 4 days and I found dead Battery today, even alarm stop blinking.

I measure the charge with multimeter, it was only about 5 volts.

What can cause that big drain?

Thanks

[Linas.P]

Something... 

You will likely going to need to chase a parasitic loss somewhere, but before that just check if your Battery is good in itself and that it is charging. Apart of that it is impossible to say - it could be anything, especially on the car which was previously in the accident. 

[Herbie]

1 hour ago, andrey77 said:

Hi. 

Car stay locked for 4 days and I found dead battery today, even alarm stop blinking.

I measure the charge with multimeter, it was only about 5 volts.

What can cause that big drain?

Thanks

As Linas says, check that the DC/DC converter is outputting about 14.5V for a start, because this is what runs the 12V systems and also charges the Battery.

Next you need to check the Battery itself. Charge it overnight at least so that it is as fully charged as it can be. You then need to have it load tested. A multimeter will only give an indication of the state of charge as it is and it could show, say, 12.5V. However, once a load is applied that voltage may drop like a stone if there's a bad cell, which is why you need to have it load tested.

Next step, now that we know we're working with things that are good, we can start looking for a parasitic draw. Items such as the clock, the radio presets, the seat memory and so on need to be alive and working, even if it's 3am and both you and the car are fast asleep. This current draw is generally accepted to be 'normal' at around 50mA or 0.05A to 60mA or 0.06A. If it's much more than that then you have a parasitic draw and the video below shows you the best way to go about finding it.

 

[andrey77]

Thank you guys!

I learned all the scenarios and decide to buy  new Battery, so far so good!

 

Rgds