State of Charge measurement design for a 48 V battery

I'd like help in designing of a circuit that would help me measure state of charge for a 48 V battery I've seen examples using lm3914 IC which gives a rough state of charge indiciation for 12 V batteries and can be used uptil 25 volt. I'd like one which will help me measure state of charge for a 48 V battery

Also I know that theres no circuit that will give State of charge per se, but will use open circuit voltage as an indicator or maybe discharging current.

Can someone help me on how to go about this.

In any case if this isnt possible can someone tell me how to come up with a rough equation to calculate SOC based on a combination of some parameters like OCV, Tempaerature etc

Note : the battery unit consists of 4 12 V batteries in series (hence 48 V )

Also is their some way i can individually find the SOC of each unit( 12V individually) and then do some calculation to get the SOC of the overall. Will this be accurate ?

Hi,

First of all, like what you said, there are different ways to measure "state of charge('')":http://batteryuniversity.com/learn/article/how_to_measure_state_of_charge You can also refer to this chart if you'd be using V open circuit, http://modernsurvivalblog.com/wp-content/uploads/2013/06/battery-state-of-charge.jpg

From the way I see it, if you will just connect them in series, there is the slim possibility that all have the same SOC. That is just my take on this. It would be best to measure it individually.

There is always a problem with a series batteries stack, they are only as good as the worst battery. There fore you have to make sure that every battery is monitored while charging to ensure they are all optimally charged. There are integrated circuits from places like TI for doing that sort of thing.
On discharge, same problem, any one battery that is not up to scratch will cause problems.
SOC systems usually rely on some test runs with a typical load, which "teaches" the processor that is used about how the batteries discharge over time, this relies on the load not changing wildly over the discharge cycle,
cheers,
Richard