battery go dead after 3 days unused. only light on is the security light thats blinks on dash. battery only 5 months old, new alternator. after charging starts fine but then when not started in several days it is dead. something must be draining it, please help, it driving me crazy

 

Welcome to the forum

 

There is not really the correct information to help. But ,
What does "DEAD" mean to you? What is the voltage?

1) The battery must be fully charged, and load tested for health.
2) Normally a battery that has been tested as good and going dead in the time you say there is something that is drawing a current.

 

Just asking what year and how many mile your CX5 has. You should check the batter connections ( see if they are clean and tight ) Jump or charge the battery and drive it to someplace that can check the battery and charging system. If it checks out good ,you have a drain. If so look for the obvious , shut the car off open the door then stay in close the door and see if anything is still on, interior lights, radio, amp for the radio , blower fan ,ect. Sometimes you can find the culprit easy. I have seen strange things like that happen . If you do have a drain, and have and know how to use a DVOM ,you can find out pretty quick. If its still under warrantee ,and the battery and charging system is good bring it to the dealer.

 

after fully charged what range should the battery be in to be healthy or bad. i am using a device that plugs into cig lighter

 

LOL those cigarette lighter devices are only volt meters nothing more.

You need to load test it. A bad battery in most cases can be charged to a full 12.5 volts but if there is a problem unless you do the chemical old school of testing it better to have it load test with a Digital Battery Load tester.

If it were the battery terminal condition you would have mentioned poor starting even after you jumped or charged the battery.

Here is my Mazda couple years ago NO apparent problems with starting but due diligence found it to be a battery on its way to fail.

07-30-2021, 09:10 AM

 

The OP should save himself time and money by taking the battery to an auto parts store like Autozone. They will load test the battery for free, this is the only way to definitively know the health of a battery. Battery age or resting DVOM voltage alone can have nothing to do with it.

 

Good post but you forgot to mention that they may need to first charge the battery to plus 12.5 volts prior the testing.