36S 52Ah LifePo4 battery pack, thoughts?

[LinusA]

Hello, Im looking for thoughts/tips about my battery pack build to a ”car”.
The battery pack will power a 80-160V motor and charged by a solar panel.

I have:
36 pieces 52Ah 3,2V LifePo4 prismatic cells
3 pieces 16s BMS + Master unit (REC)

Those cells will be serie connected.
Total Voltage: 3,2*36=115,2V
Totalt Wh: 52*115,2V= 5990Wh


Now to the part I feel a bit lost:
this is the steps I plan to do. Where Im standing now is that the cells is newly arrived, unpacked.

Step 1: top balance each cell, with a benchtop power supply.
Step 2: capacity test each cell, to check performance and if some cell need to be replaced. Will use (https://www.amazon.com/Vastarry-Ele...x=load+battery+capacity+tester,aps,205&sr=8-3 or similar)
Step 3: top balance the cells, so they have same level before connecting in series
Step 4: connect them in serie.
Step 5: connect and configure BMS.
Step 6: function test the BMS
Done

• Do I think the right way here?
• Compression? Is that needed?
• Is it possible to reduce the top balance time by top balancing 4cells at the same time?
• is Step3 needed?

I will 3d print fixings/spacers and then mount the cells and BMS in a battery box that I will build.

Best Regards

 

[TacomaJoe]

Top balancing is definitely needed and can be done in groups of 4 or more. I think you will have an issue with the BMSs. A 16S BMS is looking for 16 cells not 12. If the BMS could run 12S, I don't think 3 of them can be connected in series.

 

[s_s1]

And are there, are BMS produced for about 230 volts LifePo4 pack 72S?

 

[LinusA]

from what I understand about my BMSs, each BMS is programmable for 5-16 cells. And with a slave/master system I can connect up to 240 cells in serie

 

[s_s1]

Please write about a schematic or structure of a slave/master system. Or connect 4 16S batteries in series?

 

[OffGridForGood]

Those cells will be serie connected.
Total Voltage: 3,2*36=115,2V
Totalt Wh: 52*115,2V= 5990Wh

Not sure what type of "Car" you are planning to power here, on average an EV gets 4-5kM per kW, you are planning on a 6kW power supply, even if you have near zero losses, the range will be less than 30kM (18 miles) ?
and of course getting the car going from zero takes much more than 200W per kM, until it reaches cruising speeds.
Another consideration to be aware of: the electric motor will provide higest RPM at close to it's top voltage. Using less than the highest available voltage will cut the max RPM considerably. Get a chart for the motor that graphs the voltages RPM and Torque parameters, and use this to guide your design.
Be sure to post your progess and learning experiences!