EPEVER 4415 Xtra 24V LiFePo settings

[delta544]

Dear all,

I got a EPEVER 4415 Xtra for a small stand alone system with a 24v 280AH LiFePo.
Since its my first solar system I am currently learning. Also, please bear with me, english is not my first language.
I read a couple of articles here and I just want you to check my settings and to let me know, if I understand some settings correctly.


My LiFePo4 batterie is a DIY build with a JK BMS.
As you can see I set the Charging limit voltage lover then the Cell OverVoltage protection from the BMS, reason as to why it is 0.1V lower then in the BMS is, there was a hint in the manual that the 4415 is wiggleing +- 0.2V around the current voltage setting. I might change the Charge Limit Voltage to 28,6 later.....

As you can see the BMS has very moderate settings when it comes to the LiFePo battery, to increase the lifetime.

After configuring the EPEVER 4415 like shown in the first image I got some doubts about the Boost Charge setting.

So I changed it to this, which is the current setting:


Thanks to Mr @Browneye and his explanation within the Thread:https://diysolarforum.com/threads/s...4-settings-in-epever-tracer.17785/post-706182 I got the following understanding of the Boost Charge setting:

The MPPT will charge the battery with its maximum, till I get to 28.6V and then will continue to do so for the next 75 Minutes according to the Boost Duration time, correct. And as soon as I get to the Charging limit voltage of 28.7V, the MPPT will stop charging the battery, correct?

I set 75 Minutes, because I read in a different thread I should add 30 Minutes per 100AH, but I have also seen some suggestion to set it to 10 Minutes.


So, from my understanding, that should work fine, pretty much, or did I miss something here?

On remark here: I dont know why, but the EPEVER keeps to reduce the 'Series Number' from 8 to 6 when I reconnect to the EPEVER and Read the values from the MPPT. I always set it to 8 and press Update.......

kind regards,
Andreas

 

[Browneye]

There isn’t any value in holding cells above 3.55Vpc - they have reached full charge. The higher your voltage the shorter the duration needed.
You’ll notice they immediately settle back to about 3.4 resting voltage after charging terminates.
If you’re servicing loads set float for about 3.35Vpc. Your battery will maintain close to full charge to sundown.
3.45Vpc is considered fully charged - 99%.
Bms should not be utilized for charge limit - set your SCC to do that. Bms is a fail safe.

 

[delta544]

There isn’t any value in holding cells above 3.55Vpc - they have reached full charge. The higher your voltage the shorter the duration needed.
You’ll notice they immediately settle back to about 3.4 resting voltage after charging terminates.
If you’re servicing loads set float for about 3.35Vpc. Your battery will maintain close to full charge to sundown.
3.45Vpc is considered fully charged - 99%.
Bms should not be utilized for charge limit - set your SCC to do that. Bms is a fail safe.

Hi,
thanks for your update and your explanation.
So, I adjusted my Charging limit voltage to 28,6 (8* 3,57V) and Boost Charge to 28,5 (8*3,56) with 10 Minutes Boost charge time.


In regards to the BMS: Don´t I use the SCC correctly by limiting its Charge limit voltage to stay below the BMS charge limit?


kind regards,
Andreas

 

[Browneye]

Correct.
Just know that if any one cell reaches full charge its voltage will spike and bms will terminate all charging. You will want to watch all cells as charging reaches max voltage, adjust accordingly.

You’re dabbling with the top 1% of your battery’s SOC and capacity. There’s very little actual benefit there.

Most terminate charging at around 3.5-3.55 volts per cell, or at a 5% tail current, so you’re not bouncing off the bms max. Most charging systems don’t measure tail current, they just terminate by voltage and duration.

 

[delta544]

Hi,
I had a short chat with EPEVER support in regards to the LiFePo Settings for charging. From his explanation the charger settings should look kind of this:



The Support dude did not say I should configure it that way, but from his explanation it sounded like I should configure it like shown.
BMS needs to be adjusted.


Weird, can´t upload or attach an image...

 

[delta544]

Hi,
I tried to set up the Overvotage disconnect at 27.4 (27,6V-0,2V as per Manual) but I got an Overvoltage from Battery after been charged to 27,26V.
And now, even it dropped to 26,62 it does not recharge or delete the Overvoltage Alarm.

Why would the EPEVER stopping charging even when the Battery havent been at 27,6/27,4V.
BMS is set to 3,55V (28,4V) as Cut Off



Any ideas?

 

[Browneye]

Why is bms cutoff so low? It should be set to 3.65Vpc, or so, with a reconnect at 3.6. If you charge to 3.5Vpc or thereabouts, you should not be bouncing off the overvolt setting.

Charge controller measures the battery voltage with the charge current on top - it's not a good indicator of actual battery voltage. It may be close, but your bms will tell you battery voltage. BMS will indicate state of charge based on what you tell it the voltage values are. When the battery voltage gets to your 100% bms value it will indicate such. If you have unbalanced cells that shoot up when the battery gets to a higher state of charge, you may need to do some top-balancing to keep them more even.

You might post your settings and we can see what might be happening.

If battery voltage has dropped below your SCC setting, try just power-cycling it to reset it. It has its own max and reconnect values as well.

If you've set SCC to max charge to 27.8 it may well see the battery as full and drop to float.

Let's see your settings.