The reasons for battery voltage drop overnight
After about 60 miles driving on the highway, I used multimeter to check the battery voltage, the reading was 12.25. Then I disconnected the negative wire from the battery post. The next day I checked it agian,the voltage dropped to 10.43. My battey is only 48 months old VS. 108 month guarantee. What does cause the battery voltage suddenly drop that much?
You have a parasitic draw, from something that is either shorted or drawing juice that shouldn't be using battery power. You have a multi-meter, that's good. You need to pull eacj fuse, one at a time from both underhood PDS, (Power Distribution Center) and from the fuse box behind the flip-down coin-holder, which is a real pain unless you are a midget contortionist. It's difficult to access but can be done.
https://www.youtube.com/watch?v=zdIKNnwEjIs http://www.batterystuff.com/kb/articles/charging-articles/testing-your-battery-for-parasitic-load.html http
Now, after all that, your 4 year old battery is ready for re-cycling, use the (probably pro-rated) warranty and get a new one, A lead-acid battery warranty of 108 months is 9 years.... only a selling push... no automotive battery will last 9 years except certain conditions and/or fluke, the normal life span of a battery is 4 to 6 years , maybe some will live longer. Most folks will not even have the same car after 9 years and they (the battery seller) knows it, and who saves paperwork for 9 years and can produce that paperwork warranty.... it will just be rejected anyway But use that warranty regardless. Also Now, after re-reading your question, did you re-connect the battery cable overnight or leave it off and the voltage dropped that much? If the Neg-cable was disconnected then it's simply a battery failure and as before, use the warranty, get a new one, problem solved
