Battery life expectancy

[KasDel]

OK, my battery pack is doing fine as of now and they are only 2 years old.
I have checked the SoC 12 hours after full charge and they check 38.3 volts.
Individual batteries check 6.37 plus and minus .1 so far so good.

Now the question I have is there a point in time (three or four years down the road I hope) when the SoC will indicate that they are not charging fully and should be replaced. What would that value be? I am guessing it would be about 37 volts. I would rather not find out the hard way with a total failure.

[JohnnieB]

During the natural aging process, the storage capacity (AH) of a golf cart battery decreases and the open circuit voltage for a 50AH battery and a 500AH battery is the same, so you will most likely notice reduced cart performance and run-time before the At-Rest voltage changes very much. Basically, the At-Rest voltage (SoC voltage) tells you how full the container is, but it doesn't define the size of the container and a gallon-sized container contains more juice than a pint-sized one.

Batteries have to be load tested to determine their storage capacity. One load test protocol is to measure how long a battery will produce 75A before it drops to 1.75VPC (Volts per Cell). If the number of minutes is less than half the original number of minutes (Minutes @75A Rating), then the battery probable needs to be replaced, but there are no magic numbers since the amount of much reduction in performance and run-time that can be tolerated or endured is subjective.

You can do a form of load testing yourself. Record the At-Rest voltage, drive cart for about 10 miles (Use GPS or other means to record distance), let battery voltage recover for half an hour and record.

The distance traveled divided by the difference between the before and after SoC will tell you how far your batteries will take you for each 1% SoC and if you multiply that by 50, you have an approximation of how far the cart will go without going below 50% SoC.

As the batteries age, the max range will decrease and you can use it as a rough yardstick for battery capacity reduction over time.
If you drive the same route at the same speeds and accelerations, the guesstimates will be more accurate.

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In a nutshell: Keep your batteries as fully charged as possible and practical, clean and water regularly (Distilled water only), and replace them when they no longer perform to your needs or wants.

[KasDel]

Makes sense put that way JohnnieB. Thanks for the information!