Technical Section > Vehicle Electrics
Resting battery voltage
Frangar:
After poking about with a meter for my solar panel I’m intrigued that the resting battery voltage seems to be 12.2v. Given that a “normal” lead acid battery is full at 12.7v and 60% charged at 12.2v I’m now wondering if this is normal or I might have a dodgy battery given that the car is only 2 months old.....start/stop works fine so it might just be that the battery has slightly different chemistry from a bog standard lead acid.
Any thoughts welcome as usual!!
Gareth
Taff93:
I have the same question, had a complete battery failure after 3 years from new (on my 2015 CX-5 2.2 diesel sport Nav AWD ). dealership tested everything and said battery was ok, however it kept failing to hold charge. After a month or so of argument with Mazda they agreed top supply a new one FoC as warranty had only just expired. I am prompted to check progress of the new battery now. It appears the battery does rest at 12.2 volts (must be a result of Mazda's battery management system!!). My battery after 4 months since installed drained itself to 3.6 v after car was laid up for 5 days!! There does appear to be something of an issue here, something is slowly using power while car is at rest and I cannot find what it is yet. When not in use I check the voltage every day and it seems to drop average of 0.5 volts daily, however cannot explain the huge drop to 3.6 volts in 5 days?
Seems fine as long as the car is used regularly. Anyone any ideas or suffer similar issues. I keep the start/stop turned off now.
Graham V
Gclark87:
I remember hearing of a similar issue on a qashqai. Turned out to be the signal to shutdown the Bose amp wasn't there and so kept permeantly powered. This was after extensive work trying to trace what was using the power once car was off. Also any 12v battery in fully charged state at should read 12.5v or higher. Down at 12.2v the battery is either not fully charged or already suffering from drain if still connected when checking voltage or low electrolyte or cell beginning to breakdown inside the battery.
Hope you get it sorted. There is obviously substantial current draw if it's pulling battery down that much. I would say battery as an aside would probably need replacing if it has been discharged this low on a good few occasions.
Hope you find what it is and keep us posted.
Gclark87:
Sorry I should have seen that battery was already replaced. ::)
Taff93:
thanks for the tip re Bose amp signal, will look into that mine is Bose system. After extensive investigations since my original post there is a steady 1.2amp draw when car is at rest... and still can't find what it is. I started a new thread today on this to see if anyone out there having similar issues... I start the car and run it for 45 mins to charge battery every 4 days (at 4 days the battery is now down to 11v apprx. I changed the battery since original post too and same old issue. Original battery has sat in my garage for 11 months and still at about 12v!!
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