just replaced the car with a new alternator, voltage is fine when car is up and running at 14 volts, when car is off the voltage is at 11.4-11.5 is that normal for the battery? car is not daily driven

 

If you are checking the voltage on the battery with a meter the voltage you see with the car running is what the alternator is putting out. The battery should read at least 12.6 without the engine running. 11.4 volts is a bad battery.

 

 

You can't be reading it correctly.. The car wouldn't even start at that voltage.

 

that is what's showing on the dash, i will use a multimeter today to clarify, car is not my daily i drive it once every weekend

 

The dash voltage is normally around 0.4 volts lower than actually checking it at the battery…was the battery checked before you replaced the alternator ??…the battery may not be accepting a charge…you ALWAYS check the battery first before doing any electrical checks on the car…you may also have a large voltage drop on the charging system.

 

Voltmeter read 12v with car off

 

Voltmeter on car or using a DMM at the battery ??…If you are using a lead acid battery that is about 45% charged…did you take it to get tested ?…do you even have a voltmeter ???

 

It won't start with 12 volts. Might not even with 12.4. Run the car, turn it off and check the voltage. Record that number. Come back in a few hours.and put the voltmeter on it and record the voltage. Come back the next morning and check it again before starting the car. If it dropped, the battery is toast. That is the simplest way I can explain it. It probably was the battery to begin with. How old is the battery?

 

Walmart battery not even a year

 

If you let the battery go dead several times then it's toast no matter what the age.

 

As said, don't rely on the dash voltage with the engine off. Put a voltmeter directly to the battery as a baseline, then go inside the car and see what the car says, now you know how far it's off for future reference.

 

i did the inside was at 11.4 and my voltmeter read 12 at the battery , car starts up fine

 

That's a lot of drop with no current draw. Indicates some poor connections and/or wire condition to me. Really surprised 12 V at the battery cranks OK, I would want to see more like 12.7 V.

 

does it have anything to do with me only driving the car once a week

 

Does “what” have anything to do with driving your car once a week ??

 

the battery voltage

 

As I mentioned before:

1) have you had your battery "load tested" ??...I saw in a post you said not even a year...THAT DOESN'T MATTER !!
2) is your battery AGM or FLA ??
3) do you have and know how to use a DMM ??
4) have you voltage dropped your charging system to make sure your alternator is properly charging your battery ??
5) if your battery is not holding a charge and has more than a 15-20mA drain that will need to be addressed…if a fully charged battery that should last you around 3 weeks without charging it.

 

Buy a battery tester, something like a Foxwell or Topdon. Several options for under $100 on amazon.

 

Bad battery.

Tom