Forum Discussion

tlaffourtit's avatar
Sep 27, 2014

voltage drop

how much voltage drop is normal for a agm 12v battery or any battery if it is fully charged and connected to nothing?
  • ok, i'll give it a couple of days. thanks to all. it's great to hear other opinions.
  • tlaffourtit wrote:
    the batteries I have i float at 13.5v. once I disconnect them from the charger; I am guessing they shouldn't stay at 13.5v but drop down into the 12v range? example I had the batteries floating at 13.5 volts for a couple of hours. then is disconnected the charger and took a reading of 12.96v across the 8 battery string. this morning the reading was 12.84v. my question is; it this normal? you responded it depends on the make up of the battery. is there any other information I could get from the battery label to help?


    It can take a couple of days for the top charge excessive voltage to dissapate.

    Come back in a couple of days and tell us what you got, with nothing attached to them. If you are at or over 12.73V, then you are doing good.

    What you are seeing sounds normal to me.
  • maybe I should disconnect the sting from itself and take individual readings?
  • the batteries I have i float at 13.5v. once I disconnect them from the charger; I am guessing they shouldn't stay at 13.5v but drop down into the 12v range? example I had the batteries floating at 13.5 volts for a couple of hours. then I disconnected the charger and took a reading of 12.96v across the 8 battery string. this morning the reading was 12.84v. my question is; it this normal? you responded it depends on the make up of the battery. is there any other information I could get from the battery label to help?
  • Hi,

    Do you mean agm battery?

    Self discharge can be as little as 1% per month or as great as 1% per day. It depends on the chemistry that the battery maker is using.

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