Battery SOC Specifications

tkc100 Solar Expert Posts: 67 ✭✭✭✭
I have been looking for a good chart showing specific gravity and voltage as it relates to SOC.
Seems simple but there is quite a bit of variance between some of the figures I have found posted on the internet.
I even came upon an engineering page that stated the electrolyte specific gravity is different between different makes and applications.
I found the attached chart and it seems to be pretty representative but I thought I would throw it out there for your opinions.
What do you think, is it a fair compromise?


  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: Battery SOC Specifications

    The problem is there are so many variables when measuring SG . like weather,hot cold, phases of the moon,battery facing the north or south pole,the age of your children..
    The simplest thing to do I believe is when you first buy the battery/s get a hydrometer and a note pad and biro and note the SG of the cells are write this down. This is going to be the best figures you are going to ever get, then in the future when you test measure them you can see how close you are to those original measurements and that will give the best indicator of how well you are charging them. Use always the same hydrometer you started out with.
  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    Re: Battery SOC Specifications

    From what I have been reading I would have to agree there seems to be a number of variables.
    I use a light refracting hydrometer and I have a good DMM or at least those to variable are eliminated.
    Your suggestion is an excellent one provided your starting out with a new fully charged battery bank.
    If however you not as in my case, I'm looking for a reference point.
    A compromise if you will that gives me some place to start. Also something to refer to when figuring points like 50% discharged 80% discharged etc.
    The chart I posted is the best I have found so far and I was hoping to weight it against the experience of the members of this forum.