What is the ending voltage for amp hour rating?

[checkthisout]

If I have a new and perfect fully-charged FLA battery rated at 100 amp hours and I pull 100 amp hours of out if it, what will the terminal voltage be at the end of the 100 amp hour draw?

In other words what is the voltage floor for manufacturers when determining an amp hour rating?

[azdave]

From what I know (which isn't much) a single lead-acid cell at 0% remaining capacity would read 1.75 volts and 1.13 or less specific gravity. That means a typical 12V FLA battery would be at 10.5 volts when considered fully exhausted. I'll let the experts correct me if I'm off on this.

[SunEagle]

If I have a new and perfect fully-charged FLA battery rated at 100 amp hours and I pull 100 amp hours of out if it, what will the terminal voltage be at the end of the 100 amp hour draw?

In other words what is the voltage floor for manufacturers when determining an amp hour rating?

I would imagine it could be at 10.5V as azdave states but I would check the specs for the battery and see what it states to make sure. since each FLA manufacturer may have different specs.

[checkthisout]

Ok. So we're not really sure. Obviously I am checking other sources as well.

Is there not a standard manufacturers have to follow?

What if entity a and entity b each packaged the same battery with different brand names but entity a claims 120 amp hours with a finishing voltage of 10.6 and entity b claims 100 amp hours with a finishing voltage of 10.9 or something like that? Neither has to publish what that voltage is but one is claiming more ah than the other.

Basically my current battery bank is 3 240 ah batteries or 8640 watt hours.

When drawn down with a 37 watt load, the voltage drops from 12.8 to 12.3 or a little less than 1 kwh being used.

I was curious at what voltage would I have to drop down to in order to get that full 8640 watt hours out if the bank?

In perfect theory it should take 2500 wh to drop the bank from 12.7 to 12.3 volts correct? Again, FLA chemistry.

[SunEagle]

Ok. So we're not really sure. Obviously I am checking other sources as well.

Is there not a standard manufacturers have to follow?

What if entity a and entity b each packaged the same battery with different brand names but entity a claims 120 amp hours with a finishing voltage of 10.6 and entity b claims 100 amp hours with a finishing voltage of 10.9 or something like that? Neither has to publish what that voltage is but one is claiming more ah than the other.

Basically my current battery bank is 3 240 ah batteries or 8640 watt hours.

When drawn down with a 37 watt load, the voltage drops from 12.8 to 12.3 or a little less than 1 kwh being used.

I was curious at what voltage would I have to drop down to in order to get that full 8640 watt hours out if the bank?

In perfect theory it should take 2500 wh to drop the bank from 12.7 to 12.3 volts correct? Again, FLA chemistry.

All I know is that drawing down an FLA battery more than 40% (no matter what the load is) will first reduce the lifetime cycle count and second stress the plates which will shorten it's life.

To keep an FLA lasting as long as possible and to get the listed cycle count you should never drain it more then 25 to 30%. But again each manufacturer should post their specs indicating the max cycle rate including the depth of discharge for each cycle. They never tell you to drain it fully unless they want you to purchase a new battery.

Finally if you wire batteries in parallel (which it seems you are doing with those 240Ah type) you run the risk of unequal charging and discharging which will hurt one or more of them and shorten their life and cycle count.

[checkthisout]

All I know is that drawing down an FLA battery more than 40% (no matter what the load is) will first reduce the lifetime cycle count and second stress the plates which will shorten it's life.

To keep an FLA lasting as long as possible and to get the listed cycle count you should never drain it more then 25 to 30%. But again each manufacturer should post their specs indicating the max cycle rate including the depth of discharge for each cycle. They never tell you to drain it fully unless they want you to purchase a new battery.

Finally if you wire batteries in parallel (which it seems you are doing with those 240Ah type) you run the risk of unequal charging and discharging which will hurt one or more of them and shorten their life and cycle count.

I understand all that. My question is if the Amp hour rating assumes a dead battery if you are going to get the full claimed amount of Amp hours out.

If it does, then what is the voltage that is considered "dead" for an FLA battery.

[Bala]

The capacity you will get from a battery will depend on a lot of things. Look at the manufacturers specs for how they determined the Ah rating. 20Hr? 100Hr? etc. Discharge rate is also a factor.

In the following link in the Depth of discharge section is a table of end of "End of discharge".

https://batteryuniversity.com/article/bu-501-basics-about-discharging

This link explains a bit about Ah ratings.

https://www.batterystuff.com/kb/articles/battery-articles/what-does-20-amp-hr-rate-mean-.html

[SunEagle]

I understand all that. My question is if the Amp hour rating assumes a dead battery if you are going to get the full claimed amount of Amp hours out.

If it does, then what is the voltage that is considered "dead" for an FLA battery.

If it was up to me then any value below the battery rating (say 12V) would be bad for the battery. I would also imagine the as the battery drains it would not provide the same output (volts or amps) as it would if it was full. But that is just an assumption.