At what C rate at 3.6v/cell was a lifepo4 battery considered full again?

[Scph9002]

was it 0.05c?

I noticed yesterday when my rather large battery reached 3.6v/cell the charger dropped current really fast. Was CC charging between 35A and 50A on a 560Ah battery which is not much more than 0.05C

 

[FilterGuy]

I assume it is a LiFePO4 battery.

Yes, 3.65V per cell is fully charged.

 

[DThames]

A typical CC, CV charger will be reducing the amps after the battery gets to full voltage. For example, if 40 amps are going in at 3.55v per cell and the voltage is slowing going up (assume 3.6v per cell charge to voltage) then once the 3.6v level if reached, the amps will be dialed back more and more to prevent the voltage from going over 3.6v per cell. As the battery reaches full charge, the amps should approach zero. Regardless if you started with 20 amps or 40 amps, the behavior would be the same, just over a different time period.

 

[bobdelso]

3.6 is like 90-95% full. It takes a while to get that last few % as a good charger will drop into float mode and will put out a few amps while it tapers down.

 

[Scph9002]

A typical CC, CV charger will be reducing the amps after the battery gets to full voltage. For example, if 40 amps are going in at 3.55v per cell and the voltage is slowing going up (assume 3.6v per cell charge to voltage) then once the 3.6v level if reached, the amps will be dialed back more and more to prevent the voltage from going over 3.6v per cell. As the battery reaches full charge, the amps should approach zero. Regardless if you started with 20 amps or 40 amps, the behavior would be the same, just over a different time period.

ye ofc but i was a bit surprised how relative high c rate i could approach 3.6v and only needing a few minutes of CV untill close to 0 amps.

I mean the default CV/absorbtion time on epever ssc for lifepo4 is 2 hours.

Reaching 3,6v at 1C or 0.2C is a world of difference when it comes to absorbtion times i guess.


Anyways.. 0.05c is full?

 

[John Frum]

A typical CC, CV charger will be reducing the amps after the battery gets to full voltage.

This is misleading.
Its not the charger that reduces the current.
As the battery voltage converges with the charge voltage current naturally decreases.
Current flow is a function of potential difference between the battery and the charger.

 

[John Frum]

ye ofc but i was a bit surprised how relative high c rate i could approach 3.6v and only needing a few minutes of CV untill close to 0 amps.

I mean the default CV/absorbtion time on epever ssc for lifepo4 is 2 hours.

Reaching 3,6v at 1C or 0.2C is a world of difference when it comes to absorbtion times i guess.


Anyways.. 0.05c is full?

Lets assume a single cell with a charge voltage of 3.65 volts.
Lets also assume the cell specs say the max charge current is .5c and its a 280ah cell.
At 140amps(.5c) you will be able to get less coulombs into the cell before the voltage pops up into the high knee and the potential difference decreases to the point where the battery controls the current flow as opposed to 56amps(.2c).

 

[DThames]

This is misleading.
Its not the charger that reduces the current.
As the battery voltage converges with the charge voltage current naturally decreases.
Current flow is a function of potential difference between the battery and the charger.

Yes, you stated that better than what i said......it just happens.