Golf Car BATTERIES at SAMS?

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  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    my question specifically is this:

    voltage maxes out at 12.9V so that indicates the battery is at 100%
    if the battery drops to 12.7V... is the battery still at 100%?

    if the answer is no - then how do i figure out the SOC?
  • BB.BB. Super Moderators, Administrators Posts: 28,869 admin
    Re: Golf Car BATTERIES at SAMS?

    Charge the battery bank until the cells are bubbling (basically a light equalization). Let the bank set for three hours (no load/no charging) for the electrolyte to fully mix in the cells (and the batteries to cool to room temperature).

    Then measure the voltage and the specific gravity (and log the results).

    That will be "full charge". Monitor (and log) the battery conditions over time and you will be able to ensure that you are fully recharging the batteries (not deficit charging). And any changes will be the results of aging, temperature, and potential problems (bad cabling, failing cell, etc.).

    At this point, you need to create your own "full charge" voltage/s.g. chart. At the best, the charts that are out there are only estimates and/or the "ideal" battery. You now need to compare them to themselves.

    At best, resting voltage is just an estimate and not very practical to use on a bank that is constantly being cycled (disconnecting the bank and resting for three hours is usually not very convenient).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    right that is to get indictions of what full charge is like. but after some useage, how do i determine the SOC is 80%, 50%, 20%, etc...?

    the charts on the internet wont seem to make sense for my situation.

    followup question: i know a battery monitor might be the answer but that is if i am using the inverter for a draw. what if i dont use any power and the battery drains naturally from lack of use. the monitor will not pick up the change over time. this is the specific situation where i would like to know if my battery is 90% 80% 50%etc... SOC. question is how do i rebalance/rebaseline the SG and voltage charts all over the internet for my specific case?
  • BB.BB. Super Moderators, Administrators Posts: 28,869 admin
    Re: Golf Car BATTERIES at SAMS?

    The problem is that batteries are not ideal--and trying to "accurately" "nail" the battery bank performance is probably not worth the effort.

    The typical battery would probably lose 25% of its charge over the period of several months (AGM's probably 2-3x longer). I would guess you are recharging your bank every day--so long term losses due to storage should not be an issue.

    A battery monitor does something that is very hard for a person to do... Totalize the Amp*Hour taken in and out of the battery over time. It would be like looking at instantaneous fuel flow or MPG and trying to figure out the long term gas mileage--not easy to do accurately.

    Basically, you tell the Battery Monitor the estimated bank capacity. And the more complex ones you can program in factors that affect capacity (such as Peukert factor--where the higher current you take out, the less efficient the battery). And the Battery Monitor "resets" back to 100% when the battery "is full" (recognizes the termination of a full charge based on current drop and charging voltage).

    Does the battery monitor give an "optimistically" accurate view of the battery capacity (your battery is now at 82% capacity)--yea... But it is more accurate than a DVM and the real time numbers available for a sealed type battery (you cannot access the electrolyte to measure state of charge).

    Other than a few points (75% state of charge--long term storage causes sulfation if below ~75% SOC; cycling a battery very often below 50% SOC will quickly age it; cycling below 20% SOC will run the risk of permanent damage to one or more cells)--knowing 84% vs 88% (other than as a relative term) is just too much to expect from a bank that is not setup with laboratory style monitoring.

    If you are "measuring" within 5-10% of the "true SOC" (using your own baseline)--you are probably doing well.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    i think having revealed enough of my situation how do i even know if i am down to 80% or 50% since my sg and voltage numbers are much higher than "norm"?

    btw currently there is no charging to those batteries - panels arent up and wont be up for a long time (HOA). for now i guess its best to have the prosine charge it every week?
  • BB.BB. Super Moderators, Administrators Posts: 28,869 admin
    Re: Golf Car BATTERIES at SAMS?

    As long as you charge them before they get below 80% state of charge and get them above 90% SOC--then they should last pretty well...

    When I have storage batteries that I need to keep charge but don't have a "nice" charger with float... I just take a lamp timer and set it to turn the charger on one hour per day... Keeps the batteries charged but does not "boil them dry" (my usual problem with the standard trickle chargers on car batteries.

    I am sorry--I don't try to keep track of everyone's back-story. There are just too many posters here--and if I answer wrong because I forgot or mixed up a couple histories--then I can cause more confusion.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    ok for my condition - full charge is at 12.9V and sg is at 1300+

    what would the voltage and sg be to have the SOC be at 80%?
  • icarusicarus Solar Expert Posts: 5,115 ✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?
    mshen11 wrote: »
    ok for my condition - full charge is at 12.9V and sg is at 1300+

    what would the voltage and sg be to have the SOC be at 80%?


    Try reading here:http://www.batteryfaq.org/

    According to their chart, 75% at 80f SG would be ~1.225

    Tony
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?
    icarus wrote: »
    Try reading here:http://www.batteryfaq.org/

    According to their chart, 75% at 80f SG would be ~1.225

    Tony

    right but according to their chart 100% SOC is 1.265 SG. but my battery 100% SOC is ~1.300 SG. so for my set of battery is ~1.225SG still 75% (i do not believe it is - my guess is 75% is at some higher number but what is that number?)
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: Golf Car BATTERIES at SAMS?
    right but according to their chart 100% SOC is 1.265 SG. but my battery 100% SOC is ~1.300 SG. so for my set of battery is ~1.225SG still 75% (i do not believe it is - my guess is 75% is at some higher number but what is that number?)
    I don't know if this will help answer your question as this table is for my Deca traction battery but the SG's are closer to yours. By the way, have you checked with more than one hydrometer to check the accuracy of the one that you are using?

    Factory values:

    100% Charged = 1.285 - 1.290 Sp. Gr.
    75% Charged = 1.240 - 1.245 Sp. Gr.
    50% Charged = 1.195 - 1.200 Sp. Gr.
    25% Charged = 1.150 - 1.155 Sp. Gr.
    0% Charged = 1.115 - 1.120 Sp. Gr.

    This is an interpolated from the above factory values that I made up:

    State of Charge SG
    100% 1.285-1.290
    90% 1.275-1.280
    80% 1.250-1.255
    70% 1.230-1.235
    60% 1.215-1.220
    50% 1.195-1.200
    40% 1.180-1.185
    30% 1.160-1.165
    20% 1.145-1.150
    10% 1.130-1.135
    0% 1.115-1.120
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Golf Car BATTERIES at SAMS?
    mshen11 wrote: »
    right but according to their chart 100% SOC is 1.265 SG. but my battery 100% SOC is ~1.300 SG. so for my set of battery is ~1.225SG still 75% (i do not believe it is - my guess is 75% is at some higher number but what is that number?)

    1.258

    It's as good as any. If your 'full' reading is 102.7% of the chart's, then just compensate the other numbers accordingly. I find your 1.300 reading odd. Are you in New Orleans or Death Valley or something? :p
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    thats why i constantly ask these questions over and over again - something doesnt make sense. the temps in my garage is normal (50F to 80F) - im in NoVA

    hydrometer is standard one from sears. i may be reading it wrong :P [but i dont think i am]

    so this is more voodoo magic than exact science. if one doesnt have panels (yet)... would a geenral rule be just to recharge via battery charger once a week?
  • BB.BB. Super Moderators, Administrators Posts: 28,869 admin
    Re: Golf Car BATTERIES at SAMS?

    One way of reading the specific gravity wrong is if the electrolyte still has bubbles in it and they collect on the float... Tapping the side of the hydrometer to dislodge the bubbles from the float may be needed at times (s.g. will read high if there are bubbles on the float).

    Other than that, the hydrometer should read 1.000 when measuring distilled water at room temperature.

    I don't think you are reading it wrong... Your readings sound too consistent to be thrown off by the occasional bubble on float.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    Here is a link to the DECA service manual for the D series batteries

    http://www.eastpenn-deka.com/assets/base/0656.pdf

    There is a lot of information applicable to all lead acid batteries that might be helpful to some
  • icarusicarus Solar Expert Posts: 5,115 ✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    I was very red faced once when I, in a huff, returned a new hydometer. I discovered that I was over filling the glass such that the float was hitting the top of the bulb. I was getting very erratic readings and couldn't figure it out until the seller suggested that I try a bit less electrolite!

    One other question is, because you are getting "over charged" SG readings it is possible that that your battery is overcharged. You might also have non spec electrolite. There are cases where manufacturers use extra strong acid, particularly in cold climates if memory serves.

    Tony
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    well these are sam's club batteries (made in mexico sticker). anyone also just buy them around the time the thread was created?

    i believe those who have are getting similar results.

    well i tried to measure the sg of water.... i could not get the glass bobber to float because it is too long and it will hit the top of the vial. so this hydrometer cant measure water right?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Golf Car BATTERIES at SAMS?
    mshen11 wrote: »
    well these are sam's club batteries (made in mexico sticker). anyone also just buy them around the time the thread was created?

    i believe those who have are getting similar results.

    well i tried to measure the sg of water.... i could not get the glass bobber to float because it is too long and it will hit the top of the vial. so this hydrometer cant measure water right?

    Most battery hydrometers will not read to 1.000 - they start a bit below 1.100; usually 1.075 or so. Pure water @ 1.000 would be about another inch higher on the bobber. From there they "go up as they go down": the higher numbers are lower on the bobber. On mine, the 1.300 mark is the last thick line at the bottom. There is also a colour scale for those of us who are nearly blind; red to white to green. If it reads in the green, it's fine. But it is possible to interpret 1.275 as 1.300, as the thick line for 1.275 appears just above the 1.300 number:

    1.275
    1.300

    The green starts at 1.265. I've just been going cross-eyed trying to make this out, the lines are so small. Maybe that's the problem. Maybe I'm still not seeing it right, so others will correct me if this is so. Your actual hydrometer may very, batteries not included. (Closed course; professional driver. Do not attempt. Et cetera. :p)

    Green is good.
    White is all right.
    Red is dead.
    :p
  • mshen11mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    mine is green white red also - so we probably have the same thing.

    its just someone mentioned trying to test the hydrometer w/ water at 1.00 and i figured its a good idea :)

    well i was about to return my hydrometer (heading out for the day in 20mins). i guess ill keep it after all.
  • bryanlbryanl Solar Expert Posts: 175 ✭✭✭✭✭
    Re: Golf Car BATTERIES at SAMS?

    re a
    link to the DECA service manual for the D series batteries
    - thanks Mike!

    I just wish some of those who get into the "thick plates deep cycle" is a primary issue thing would take a serious and critical look at the pamphlet's pictures and descriptions and see how a battery is actually made.

    There's also a very good glossary for Niel as well.
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