# CSB batteries Constant Current Discharge Characteristics

I'm comparing batteries for use in UPSes and during my tests I was consulting the datasheets of 2 manufacturers. The datasheet from SunLight is crystal clear but CSB's datasheet is using terminology that I haven't seen anywhere else and googling didn't help. Here's the table from the later regarding discharge time:

Does anybody understand anything from this table? What is F.V/Time? What are the numbers of the table correspond to?

What is F.V/Time?

The "F.V/Time" label is explaining 2 things:

1. The values below that label (i.e. down the left column) are the final voltage (F.V.) values for each cell (there are 6 cells in that 12 V battery) for which information is given;
2. The values to the right of that label (i.e. across the top of the table) are the specific Time values which are given (2 mins, 4 mins etc.)

So "F.V/Time" is trying to explain what the values mean, in both the rows and in the columns.

Does anybody understand anything from this table?

This table shows the relationship between 3 variables: cell final voltage (F.V.) (down the left side), discharge time (across the top), and current (values in each cell). So if you know 2 values, you can find the third.

For example: If you have a 20 A load and don't want to discharge the battery below 10.5 V (= 1.75 V per cell) then assuming you start from a fully-charged battery, how long can you draw that current?

(Image source: Adapted from the question, originally from CSB HR 1234W datasheet.)

Answer: Look along the "1.75 V" line, and you see that the battery could supply 23.5 A for 10 mins or 17.4 A for 15 mins. A graph from the manufacturer would be helpful (since the discharge current vs. time plot is a curve and not a straight line). However using a linear interpolation between those two given values (23.5 A for 10 mins, and 17.4 A for 15 mins), a 20 A load will last something like 12.9 minutes.

What are the numbers of the table correspond to?

They are the load current values, corresponding to the time (in a given column) for which that current can be drawn, down to the final voltage per cell (F.V.) in a given row.

• Thanks for your time @SamGibson – ndemou Apr 16 at 8:10