DenCo™ - Can you believe it?

This large 280Ah LiFePO4 prismatic build incorporates a milk crate as a carry/protection container. It uses a 250A Daly BMS, to allow for powering a WZELB 3000w 12V 120V Pure Sine Wave inverter. This is the largest capacity battery build that DenCo has made to date.

This battery backup power system utilizes a Victron Bluetooth SmartShunt™ rated at 500A for monitoring voltage, amperage, and consumption stats on a mobile phone. It also uses a 300A resettable marine/automotive circuit breaker as a sort of on/off switch. It incorporates positive and negative 250A terminal buses for easy connectivity to multiple loads. All connections to battery, shunt, breaker, and terminal buses are with 1/0 gauge welding cable to permit high draw applications. (Marine grade lugs were crimped with a TEMCo Hammer Lug Crimper Tool. Liberal use of zip ties and self-tapping #8 screws for mounting and securing items to the milk crate.)

When originally testing the cell balance, I found that the first cell in series charged high and was 0.3V higher at BMS charge cutoff than the other cells. Because of this I also added a 4S LifePO4 Active Balancer Board that I had on hand to even out the cells when max charge was reached. Discharge voltage was fairly even during a 102Ah drain test.

Total build cost: $1235.12 (not including crimper tool).
Total power: 3.5kWh at battery. With 85% inverter conversion efficiency (at worst), 3kWh estimated for AC power usage.
Total time for parts receiving to completed build: 3 months (mostly waiting for China shipments).

General Specs:
Created: April 11, 2021.
Cells: VariCore 280Ah prismatic 3.2V LiFePO4 cells, 4 cells in series.
BMS: Daly 250A 4S 12V common port BMS with fan.
Configuration: 4S1P (4 series).
Nominal Voltage: 12.8V.
Overall weight (with all components and inverter): 67.0 lbs (30.39 kg).
Current owner: AD6DM Dennis

Cell Specs:
VariCore prismatic 280Ah cells with M6 screws and plated copper bus bars included.
Source: AliExpress (China)
Shell Material: Aluminium
Rated Capacity: 280Ah
Internal impedance: 0.1-0.3mΩ
Nominal Voltage: 3.2V
Dimensions: 174x72x205mm
Weight: 5.22kg
Max continuous discharge current: 280A (1C)
Max recommended charge current: 140A (0.5C)
End of discharge voltage: 2.5V
Charge voltage: 3.65V
Cycle life (80%DoD): 4000 cycles
Charging temp: -5~60°C
Discharge temp: -30~60°C

BMS Specs:
Daly 4S 12V with cooling fan LiFePO4 Lithium Battery Protection Board 3.2 BMS with Balance 250A
Discharge current: 250A
Discharge overcurrent protection: 600A±100
Internal resistance: <=20mΩ
Charge voltage: 14.6V
Charge current: 125A
Overcharge detection voltage: 3.75V±0.05
Overcharge protection delay: 1sec
Overcharge release voltage: 3.55V±0.05
Balance opening voltage: 3.5V
Balance release voltage: 3.5V
Cell balance current: 30mA±5
Over-discharge detection voltage: 2.2V±0.1
Over-discharge detection delay: 1sec
Over-discharge release voltage: 2.7±0.1
Discharge overcurrent protection delay: 1sec
Discharge overcurrent protection release condition: Remove load
Short circuit protection condition: Outer short circuit
Short circuit detection delay: 960μs
Short circuit proection release condition: Remove load
Self-consumption working current: 500μA
Sleep current (battery over-discharge): 0μA
Operating temperature: -20 to 70°C
Storage temperature: -40 to 80°C
Insulated flame retardant plastic shell
Smart temperature-activated fan
Pure aluminum heatsink
High current copper plate with 3mm pure copper interface
Insulated fixing plate
Waterproof, dust-proof, shockproof closed injection glue design
Dimensions: 235mm x 130mm x 52mm