Problems with system integration with new LiFePO4 batteries in an RV....

murphylawe

Mad Scientist
Joined
Dec 6, 2019
Messages
23
Location
Southern Arizona
Howdy All,

It's Murph here and I have just upgraded from a 24v AGM battery stack (8 AGMS @ 100ah each) to a 16-cell stack made up of 280ah LiFePO4 cells. I am using (2) Daly 150amp BMS units for control.

I am having trouble integrating the upgraded system, and can't get the batteries to top-off.

I am using a 4000w AIMS 24v Inverter/Charger and it is set up for Li-Ion. I am in contact with AIMS as this alone should take the stack to 28.8 v

The solar array is made up of (8) Trina 275w Solar Panels and feed into a MDT MPPT Controller. I have never had a problem with this controller and it too is set for 28.8v and for Li-Ion.

I can't image both are incapable of charging this stack to 28.8v and I am unable to get it above 26.7

SO... I am inexorably led to the DALY 150amp BMS units. I am including screenshots of the BMS settings, and an image of the my monitor. I have checked with a multimeter and all are correct +/- within 2-3/100ths of a volt.

Ideas or thoughts would be appreciated.

I replaced this:
IMG_0003.jpeg

With this:

IMG_0161.jpeg

Here are the BMS settings:

Protection Parameters Screen 1

Cell Volt High Protect: 3.65v
Cell Volt Low: 2.22v
Sum Volt High Protect: 28.80v
Sum Low Volt Protect: 17.70v
Diff Volt Protect: 0.080v D
Charge Overcurrent Protect: 225a D
Discharge Overcurrent Protect: 225a D

Cell Charactteristics Screen 2

Type of Battery: LiFePO4
Rated Capacity: 280.0nah
Cell Reference Volt: 3.2v
Sleep Waiting Time: 3600s D
SOC Set: 39%
Balanced Open Start Voltage: 3.310v
Balanced Open Diff Voltage: 0.050v


Collect Board Settings Screen 3

Collect Boards Num: 1
Board 1 Cell Num: 8
Board 2 Cell Num:
Board 3 Cell Num:
Board 1 Temp Num: 1
Board 2 Temp Num:
Board 3 Temp Num:

Temp Protect Settings Screen 4

High Temp Protect: 65C
Chg Low Temp Protect: 10C
Discharge High Temp Protect: 70C
Discharge Low Temp Protect: 0C
Diff Temp protect: 15C
MOS Temp Protect: 47C

IMG_0011.jpegIMG_0012.jpegIMG_0012.jpeg

IMG_0018.jpegIMG_0019.jpeg

IMG_0006.jpeg
 
Last edited:

sunshine_eggo

Happy Breffast!
Joined
Oct 26, 2021
Messages
4,785
Location
USA
How long did it take you to top balance your cells?

I don't see any settings screens.

When you see 26.7V, do you still see charge current flowing into the batteries?
 
Last edited:

Quattrohead

Solar Addict
Joined
Oct 13, 2021
Messages
401
You need to change the per cell voltage to 3.5v in the BMS. Absolute max voltage per cell recommendation seems to be 3.65v
 

jimcalf

Solar Enthusiast
Joined
Aug 1, 2020
Messages
72
Location
Akron, OH
Did you top balance your cells to 3.60 or 3.65 and then hook up the BMS and set the capacity to 100%? It took me a long time to fully top balance to 3.65, but once I did, the BMS was really happy and allowed me to charge fully. I use the Victron defaults of 28.4V absorption, 1hr absorption delay (to promote balancing) and 27v float. Seems to work great. Until I properly top balanced, I always had that one cell that ramped up way faster.
 
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