Charging for Tesla Model 3 21700 cell questions

[Tres]

I am thinking of making a big battery pack like 14s14p or so with the model 3 2170 cells.

1. What would the charging and float voltages be for my mppt? I have guessed 58.8 charge and 57 float but want to be sure. I'll be using a Victron 150/45 Smartsolar mppt most likely. I know that a full battery is 4.2v but 4.1 is recommended.

2. I will be using a 60a bms. These are safe to charge at 3a so isn't that distributed x 14 for parallel? 42ah charge rate?

3. What if I made 2 or 3 packs and put them in parallel for capacity. Could I hook up a charger to one end pack, or do I need to somehow split the charging (and discharging ) between the 3 packs. Seems like you could connect them all in parallel and then charge the top one. Similar to the titan.

Battery specs:

Voltage: 3.7V

End of Charge Voltage: 4.2V

End of Discharge Voltage: 2.5V

Capacity: 4800mAh

Nominal Stored Energy: 17.76Wh

Chemistry: Lithium-ion (NCA)

Internal Resistance: 12-14 mΩ

Standard Charge: 3,000 mA: CC-CV 100 mA cut-off

Quick Charge Current: 10,000mA

Max Continuous Discharge Current: 15000mA

 

[snoobler]

I am thinking of making a big battery pack like 14s14p or so with the model 3 2170 cells.

1. What would the charging and float voltages be for my mppt? I have guessed 58.8 charge and 57 float but want to be sure. I'll be using a Victron 150/45 Smartsolar mppt most likely. I know that a full battery is 4.2v but 4.1 is recommended.

2. I will be using a 60a bms. These are safe to charge at 3a so isn't that distributed x 14 for parallel? 42ah charge rate?

3. What if I made 2 or 3 packs and put them in parallel for capacity. Could I hook up a charger to one end pack, or do I need to somehow split the charging (and discharging ) between the 3 packs. Seems like you could connect them all in parallel and then charge the top one. Similar to the titan.

Battery specs:

Voltage: 3.7V
End of Charge Voltage: 4.2V
End of Discharge Voltage: 2.5V
Capacity: 4800mAh
Nominal Stored Energy: 17.76Wh
Chemistry: Lithium-ion (NCA)
Internal Resistance: 12-14 mΩ
Standard Charge: 3,000 mA: CC-CV 100 mA cut-off
Quick Charge Current: 10,000mA
Max Continuous Discharge Current: 15000mA

1. 4.05V/cell peak, 3.3V/cell min. This will keep you in the middle 60% (using 20-80% SoC) for maximum cell cycle life based on my own personal testing of NMC cells, which tracks with many online resources. Float should be a little under peak, and set a re-bulk around 2V below that.

2. Yes, you may mostly split the current between the parallel cells. Good to assume something like 80% of that number as the load won't be perfectly split.

3. Personally, I would build a single 1 XP14S pack and get a bigger BMS to handle it, or use a BMS that uses separate high current relays.

Each and every cell should be fused.

 

[Tres]

1. 4.05V/cell peak, 3.3V/cell min. This will keep you in the middle 60% (using 20-80% SoC) for maximum cell cycle life based on my own personal testing of NMC cells, which tracks with many online resources. Float should be a little under peak, and set a re-bulk around 2V below that.

2. Yes, you may mostly split the current between the parallel cells. Good to assume something like 80% of that number as the load won't be perfectly split.

3. Personally, I would build a single 1 XP14S pack and get a bigger BMS to handle it, or use a BMS that uses separate high current relays.

Each and every cell should be fused.

I really appreciate the info. On #3, I was thinking of breaking up the battery into 2 or 3 and building it in pelican cases so it could be moved. I know when I did my 3 battleborns in parallel I took a positive off of 1 end and a negative off of the other for output and charging. Didn't know if these packs needed to be the same.

 

[snoobler]

Explore the "Wiring" link in my sig for Victron's wisdom on such things.

 

[razvangsm2002]

I am thinking of making a big battery pack like 14s14p or so with the model 3 2170 cells.

1. What would the charging and float voltages be for my mppt? I have guessed 58.8 charge and 57 float but want to be sure. I'll be using a Victron 150/45 Smartsolar mppt most likely. I know that a full battery is 4.2v but 4.1 is recommended.

2. I will be using a 60a bms. These are safe to charge at 3a so isn't that distributed x 14 for parallel? 42ah charge rate?

3. What if I made 2 or 3 packs and put them in parallel for capacity. Could I hook up a charger to one end pack, or do I need to somehow split the charging (and discharging ) between the 3 packs. Seems like you could connect them all in parallel and then charge the top one. Similar to the titan.

Battery specs:

Voltage: 3.7V

End of Charge Voltage: 4.2V

End of Discharge Voltage: 2.5V

Capacity: 4800mAh

Nominal Stored Energy: 17.76Wh

Chemistry: Lithium-ion (NCA)

Internal Resistance: 12-14 mΩ

Standard Charge: 3,000 mA: CC-CV 100 mA cut-off

Quick Charge Current: 10,000mA

Max Continuous Discharge Current: 15000mA

Hi!
i want also tu vuild a big pack 48v 30Ah
please want is the solution to welt (spot)
poitive, because I discover that is alumnium.
Thak you a lot for your time!