Definitions
Here are the definitions of the words currently used when it comes to batteries...
Powerbucket Specifications
This table contains the main characteristics of the Powerbucket
Item | Value | Why ? |
Number of cells in parallel in one module | 5 * 14 = 70 | Fits well in my wooden bucket |
Number of modules in a string | 15 | Fits well in my bucket AND is OK for my inverter |
Nominal Powerbucket stack voltage | 15 * 3.6 = 54 Volts | Well In the input voltage range of my inverter (38 to 66 V DC) |
Minimum Powerbucket stack voltage | 15 * 3.0 = 45 Volts | Well above the minimum input voltage of my inverter (38 V DC) |
Maximum Powerbucket stack voltage | 15 * 4.2 = 63 Volts | Well below the maximum input voltage of my inverter (66 V DC) |
Number of cells in phase A | 15 * 70 = 1050 cells | Number of modules in series times the number of cells per module |
Nominal voltage of one cell | 3.6 V | This is the average voltage of one cell during discharge. |
Capacity of one cell | 2900 mAh | I will use PANASONIC NCR18650PF cells having 2900 mAh capacity |
Energy in one cell | 3.6 * 2.9 = 10.44 Wh | Nominal voltage in volts X nominal capacity in Ampere hour = nominal energy stored in Watt hour |
Total energy in the Powerbucket stack in phase A | 10.44 * 1050 = 10962 Wh | |
Number of... |
Hello,
I just stumbled on your project, and it is very impressive! I'm very interested since I started looking at building a similar solution for my sailboat!
However, I just have a question regarding the capacity of your Phases. It seems to me that your calculations are wrong.
Since there is only 70 cells in parallel in a module, it seems to me that the capacity of the module is 10.44Wh*70 = 730.8Wh. Now, even if you were to put 100 of those modules in series, this would only serve to augment the voltage, not the capacity of the powerbank, that would stay at the nominal capacity of one module (730.8Wh). Now, if you were to connect your modules in parallel, then the capacity would be 10950Wh, but with a voltage of 3.7V.
Am I mistaken here? What am I missing?