What's the lowest voltage to maximize lifepov4 usability?

[Stephen Shreds]

Hey guys I just installed my battery in my van and I am wondering what I should have my low voltage disconnect set to to maximize my usable watt hours. In wills video he says I should set it to setting two. But that's 9.5v. isn't that way to low for a lithium battery?

I am seeing alot of mix opinions on this subject. I will be moving to Alaska soon and I want to square everything up when I'm here in California.

 

[jasonhc73]

How many "cells" does your battery have? Can you configure your charger? Can you configure your BMS (Do you have a BMS?)

LiFePO4;
The extreme limits: 2.0V to 4.2V
The consensus for maximum longevity is: 2.5V to 3.65V (If you 5 cells, 9.5V÷4cells=2.35V/cell)

The 2 basic factors that affect longevity;
Temperature and C Rate

Temperature - The closer to your human comfort environment the better.
C rate - Charge/Discharge rate (How much amps pushing or pulling, aka Battery Coulomb Rate), a 1 C Rate uses the entire battery in 1 hour.
The closer to 0.5 C or less (0.2 C rate ideally) the longer the battery will last.

 

[Stephen Shreds]

8 200ah cells in parallel series is my battery.

 

[Stephen Shreds]

How many "cells" does your battery have? Can you configure your charger? Can you configure your BMS (Do you have a BMS?)

I do have a bms.

It's a Daly bms idk how to change the parameters for it.

 

[jasonhc73]

8 200ah cells in parallel series is my battery.

What I think I see you mean is you have 4S2P(or 2P4S), set up for a 12V setup.
So the absolute lowest recommend Voltage to discharge to is 10V. and max to charge to 14.6.
That is not the extreme limits, and basically what Battleborn and every other "namebrand" sets their bms to.

 

[Stephen Shreds]

LiFePO4;
The extreme limits: 2.0V to 4.2V
The consensus for maximum longevity is: 2.5V to 3.65V (If you 5 cells, 9.5V÷4cells=2.35V/cell)

Is that a typo? If I have 4 cells,9.5v ÷4 = 2.35 correct?

 

[Stephen Shreds]

What I think I see you mean is you have 4S2P(or 2P4S), set up for a 12V setup.
So the absolute lowest recommend Voltage to discharge to is 10V. and max to charge to 14.6.
That is not the extreme limits, and basically what Battleborn and every other "namebrand" sets their bms to.

4 Parallel pairs into series. There we go haha had to look it up.

 

[jasonhc73]

Is that a typo? If I have 4 cells,9.5v ÷4 = 2.35 correct?

That is correct. The extreme ends of LFP cells is where almost all the damage happens. LFP (aka LiFePO4) cannot be recovered once the damage happens, the chemical process is one way.

 

[jasonhc73]

4 Parallel pairs into series. There we go haha had to look it up.

Take a picture!

 

[Stephen Shreds]

Take a picture!
[/QUOTE]

 

[nwillitts]

can i charge my byd batts to 58v?use them down to 40v?

 

[Picasso]

@nwillitts For used cells you need to look at each cell voltage at the top and bottom of your charge, when you see the voltage difference of the cells above 200mv'ish you should set you charge and discharge based on that. For two BYD packs in series your low will be around 46 and high 55. that is playing it safe. But look what voltages yours cells drift at.

 

[nosys70]

you can charge a cell up to 4.2V but it is proven that this voltage does not stay long , it goes slowly back to 3.7 even if you do not use the battery. If you use it, it goes also very fast to 3.7 , so the increased time imho does not worth the wear (loss of cycles) you put on the battery.
the same for the under 2.5V , that give you almost nothing in term of time.
This is not true for small devices, where the discharge rate could be very low in regard of the battery capacity (very low C)
as you can see most of the usable range of the battery is between 3.4 and 3.0V and if you charge to 3.5, 3.6, 3.7 you obtain more or less the same capacity