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# F.V/Time - when talking battery capacity - means "Fixed Load" results in an X volt S.O.C o

## F.V/Time - when talking battery capacity - means "Fixed Load" results in an X volt S.O.C o

(OP)
People keep seeing this term "F.V/Time" on manufacturer's battery data sheets and asking what it means.

I've seen numerous absurd answers in various places. This is the only forum where I found a sort-of correct answer, but the guy who wrote it didn't even realize what the question was... only happened to pen the answer in the course of a rambling post about different ways to calculate a given battery's capacity.

So, here is what F.V/Time means:

The "F" stands for "Fixed" (as in "fixed load") and the "V" of course means "Voltage" and "Time" means "time" (duh...)

So, a chart that showed something like:

F.V/Time | 60 min. | 120 min. | 180 minutes
11.10v | 200 watts | 122 watts | 90 watts

...is telling you that if you draw a fixed load of 200 watts from a 12v battery, after 1 hour the battery voltage will have dropped to 11.10 volts (and the battery will be almost completely discharged). With a fixed load of only 122 watts you could go 2 hours before the battery got down to 11.10 volts... and if your fixed load was only 90 watts you could get 3 hours of energy out of the battery before discharging it down to 11.10 volts.

As far as I know, this term "F.V/Time" is not really official engineering shorthand, just something battery manufacturers have come up with to create charts showing battery capacity if a given fixed load is drawn from it for a given length of time.

If I'm wrong about this, somebody who really, for sure knows that the term means something else, please illuminate the rest us. And please don't tell me it stands for "Family Violence"-- which is what you'll be told if you try to do a Google search for the term (and they claim they've improved search algorithms...)

-- J.R.

### RE: F.V/Time - when talking battery capacity - means "Fixed Load" results in an X volt S.O.C o

You are asking about what appears to be a non-engineering term, and then maybe have a typo in the term?

Surely you jest!

So was it a trick nonsensical rhetorical theatrical question? Or are you serious?

If you are serious, I apologize, and simply suggest you confirm or deny a typo.

Do mean F.V/time or do you mean F.V./time?

Us engineers are sometimes rather picky about details....

### RE: F.V/Time - when talking battery capacity - means "Fixed Load" results in an X volt S.O.C o

I don't think that it's a "term;" it's simply the labels for the two axes of data. And, I think it's FINAL Voltage, which is the leftmost column, and Time, which are the columns of discharge current. see page 15 of http://www.alpha.com/Media/documents/010337B1001A_..., where final voltage is used.

Note in Mike's cites, the usage is F.V./Time, which is a brute force shorthand for labeling the leftmost column and topmost row. Tables are annoying that way. Unless you do what they did, you'll have to add a row just for "Time," which is obviously a gross waste of page space.

If you do a search for "final voltage" and uninterruptible power supply, you'll see it used quite often. BTW, note that there is a power supply forum.

TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

### RE: F.V/Time - when talking battery capacity - means "Fixed Load" results in an X volt S.O.C o

I agree it IS Final Voltage.

Keith Cress
kcress - http://www.flaminsystems.com

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