Project 1 Mechanical design of battery pack
ANR26650M1B, 3.3 Volts, 2.6Ah (LiFePO4) Battery
cell information is present here:
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.batteryspace.com/prod-specs/6610.pdf
LithiumWerks (manufacturer) ANR26650M1B Specifications
| Manufacturer: | LithiumWerks |
| Mfg PN: | 300832 |
| Chemistry: | Lithium Iron Phosphate (LiFePO4) |
| Voltage: | 3.3 Volts |
| Capacity @ 25°C: | 2.6 Ah |
| Energy @ 25°C: | 8.25 Wh |
| Specific Power: | > 4000 W/kg (@ 25°C, 2sec pulse) |
| Impedance: | > 6 mΩ (1kHz AC) Typical) |
| Cycle Life: | > 4000 Cycles (@ 1C/1C, 100% DOD) |
| Dimensions | |
| Height (max): | 65.15 (+/- 0.5 mm) |
| Diameter (max): | 25.96 (+/- 0.5mm) |
| Product Weight: | 76.0 (+/- 1.0 g) |
| Warranty: | DOA |
cell specifications from PDF:
battery parameters have a considerable amount of effect on how the final vehicle will perform, so design criteria should be solid and sound. some of the vehicle characteristics affected are:
- maximum traction motor torque
- maximum regeneration brake torque
- vehicle range
- vehicle total weight
- vehicle price
battery parameters have a considerable amount of effect on how the final vehicle will perform, so design criteria should be solid and sound. some of the vehicle characteristics affected are:
maximum traction motor torque
maximum regeneration brake torque
vehicle range
vehicle total weight
vehicle price
4 core input parameters for electric vehicle design are:
battery chemistry
battery voltage
average energy consumption of the vehicle on a driving cycle
final vehicle range required
battery chemistry: The type of elements contained within a battery and the chemical reactions during discharging-charging events define the chemistry of a battery.
A battery cell consists of five major components: electrodes – anode and cathode, separators, terminals, electrolytes, and a case or enclosure. For automotive applications, there are different types of cells used in Individual battery cells which are grouped into a single mechanical and electrical unit called a battery module. The modules are electrically connected to form a battery pack.
The voltage level of the battery determines the maximum electrical power which can be delivered continuously. Power P [W] is the product between voltage U [V] and current I [A]:
P = U* I
The higher the current, the bigger the diameter of the high voltage wires and the higher the thermal losses. For this reason, the current should be limited to a minimum, and the nominal power obtained by having a higher voltage. For our application, we are going to consider a nominal voltage of 400 V.
Battery pack architecture:
All high voltage battery packs are made up from battery cells arranged in strings and modules. A battery cell can be regarded as the smallest division of the voltage.
Individual battery cells may be grouped in parallel and/or series as modules. Further, battery modules can be connected in parallel and/or series to create a battery pack. Depending on the battery parameters, there may be several levels of modularity.
The total battery pack voltage is determined by the number of cells in series. For example, the total (string) voltage of 6 cells connected in series will be the sum of their individual voltage.
steps involved to build the batteyr parameters and configuration are as follows:
it starts with calculations of an individual cell first:
--------------------------------------------------------------
single cell calculations:
volume :
dimensions: r=0.013m and h=0.065m
volume one cell (according to the formula) [m^3]: 0.03451 cubic meters
one cell energy capacity [Wh] = Cell Capacity (Ah) × Cell Voltage (V)
= 2.6 * 3.3
= 8.58 Wh
single cell energy density (volumetric energy) [Wh/m^3]
= one cell energy capacity / volume one cell
= 8.58 / 0.03451
= 248.62 Wh/m^3
Gravimetric energy (Wh/kg)
= Single Cell Energy / Single Cell Mass
= 8.58 Wh / 0.076 kg
= 112.89 Wh/kg
--------------------------------------------------------------------
battery pack assumptions:
Km/KWh = 250 / 18.121
nominal voltage series connection = 145.2 V
average energy per Km
= 18120.96 / 250
= 72.483 Wh/km
Number of cells connected in series
= Nominal voltage of series connection / Nominal voltage of a single cell
= 145.2 V / 3.3 V
= 44
Energy for battery pack (wh)
= No. of cells connected in series x Single-cell energy
= 44 x 8.58 wh
= 377.52 wh
Number of cells connected in parallel
= Battery pack total energy (wh) / Energy for battery pack (wh)
= 18120.96/377.52
= 48
Battery pack capacity
= No. of cells connected in parallel x Single cell capacity (Ah)
= 48 x 2.6 Ah
= 124.8 Ah
Total number of cells for battery pack
= No. of cells connected in parallel x No. of cells connected in series
= 48x44
= 2112
Mass of battery pack
= Total no. of cells for batter pack x Mass of single cell
= 2112 x 0.076 kg
= 160.512 kg
Total volume of the battery pack
= Total no. of cells for batter pack x Volume of single cell
= 2112 x 0.0345
= 72.89 m^3
Cell peak current (A)
= C rate (Max Pulse Charge Current) x Single cell capacity
= 20 x 2.6
= 52 A
Battery pack peak current (A)
= Cell peak current x No. of cells connected in parallel
= 52X48
= 2496 A
Battery pack peak power (W)
= Battery pack peak current x Voltage of series connection
= 2496 A x 145.2 V
= 3624192 or 362.42 W
Cell continuous current (A)
= Crate (Max Continuous Charge Current) x Single cell capacity
= 10 x 2.6
= 26 A
Battery pack continuous current (A) - current to charge the whole battery
= Cell continuous current x No. of cells connected in parallel
= 26 x 48
= 1248 A
Battery pack continuous power (W)
= Battery pack continuous current x Voltage of series connection
= 1248 x145.2
= 18120.96 or 18.120 KWh
nickel strips are used for cell-to-cell connections.
Nickel Strips
Nickel strip is generally used in battery building. Its due to its efficiency of usage in spot welding and soldering as well its high corrosion resistance over time. It has good properties and excellent resistance to many corrosive environments. The pure nickel will never get rust after it applied to battery packs. It won’t affect the current transfer between batteries.
Pure nickel strips are the material you want, but many vendors swap out it for nickel-plated steel strips, which are poorer and have greater resistance – not suitable for most battery projects.
It also solder incredibly quickly, so you can weld them onto your existing busbar connections to raise the supply of current you can pull through the busbars. The benefits are nearly limitless!
then to dampen the shocks (if any in the battery), the cells are covered in a hard plastic enclosing from the top and bottom. this fits into the battery pack when many such configurations are aligned inside the casing as shown below.
Assumed battery enclosure used (reference: https://www.novelis.com/automotive/electric-vehicle-battery-enclosure/)
advantages:
• Up to 50 percent lighter than an equivalent steel design
• Best-in-class mass energy density at more than 160
watt-hours per kilogram, an extremely efficient design
for OEMs and Tier 1 battery pack manufacturers.
• Accommodates all battery cell types and is designed
particularly for battery electric vehicles with larger
power packs such as pick-up trucks, sport utility
vehicles and crossovers.
• Most cost-effective aluminum solution for mass
production electric vehicles when compared to
aluminum extrusion and casting-intense designs.
• Low price premium on $/kg saved compared
to equivalent steel designs at substantially
lower weight.
finalbattery pack image (supposed to fit in a car chassis):
final configurations of the battery pack:
nominal voltage series connection = 145.2 V
average energy per Km (Wh/km) = 72.483 Wh/km
Energy for battery pack (Wh) = 377.52 Wh
Number of cells connected in parallel = 48
Number of cells connected in series = 44
Battery pack capacity = = 124.8 Ah
Total number of cells for battery pack = 2112
Mass of battery pack = 160.512 kg
Total volume of the battery pack = 72.89 m^3
Cell peak current (A) = 52 A
Battery pack peak current (A) = 2496 A
Battery pack peak power (W) = 362.42 W
Cell continuous current (A) = 26 A
Battery pack continuous current (A) = 1248 A
Battery pack continuous power (W) = 18.120 KWh
one of the reference sources:
https://x-engineer.org/automotive-engineering/vehicle/electric-vehicles/ev-design-battery-calculation/#:~:text=The%20high%20voltage%20battery%20it,maximum%20regeneration%20brake%20torque