Lithium Ion Battery Pack (18650)
Assumptions
18650 Battery Assumptions
| Specification | Value |
|---|---|
| Nominal Voltage | 3.7v |
| Max Voltage | 4.2v |
| Cutoff Voltage | 3.0v |
| Capacity | 2500mAh |
Battery Spec 3S30P - 60Ah
| Specification | Value |
|---|---|
| Nominal Voltage (3 x 3.7v) | 11.1v |
| Max Voltage (3 x 4.2v) | 12.6 |
| Min Voltage (3 x 3.0v) | 9v |
| Cells in Series for Voltage | 3 |
Parallel Cells to Get Capacity 60Ah/2.0Ah | 30 |
| Total Cells Required | 90 |
Dimensions (mm) | (long pack) =18*3 x 18*30 x 65 =54mm x 540 mm x 65mm (3 rows on 30 cells) =18*9 x 18*10 * 65 =162 x 180 x 65 4.25” x 10.6” x 2.6” |
If battery stops being useful at 10.8 for some appliances (AC Inverter), then we would end up getting 50% the capacity of the 3S battery pack.
My solar battery charger supports the 3S configuration.
Pack Distribution
Using rePackr.com:
Pack Dimensions
| Dimension | mm | inches |
|---|---|---|
| Width | 108 mm | 4.25" |
| Length | 270 mm | 10.6" |
| Height | 65 mm | 2.6" |
Battery Spec 3S40P - 80Ah
| Specification | Value |
|---|---|
| Nominal Voltage (3 x 3.7v) | 11.1v |
| Max Voltage (3 x 4.2v) | 12.6 |
| Min Voltage (3 x 3.0v) | 9v |
| Cells in Series for Voltage | 3 |
Parallel Cells to Get Capacity 80Ah/2.0Ah | 40 |
| Total Cells Required | 120 |
Battery Spec 4S20P - 40Ah
| Specification | Value |
|---|---|
| Nominal Voltage (4 x 3.7v) | 14.8v |
| Max Voltage (4 x 4.2v) | 16.8v |
| Min Voltage (4 x 3.0v) | 12.0v |
| Cells in Series for Voltage | 4 |
Parallel Cells to Get Capacity 40Ah/2.0Ah | 20 |
| Total Cells Required | 80 |
Would need to step down the voltage to 12v which may introduce some losses but would allow us to use the full capacity of the batteries.
Test Results of Batteries
Spreadsheet: 88af-18650.xls
Battery Examples
Tesla's Power Wall
| Capacity | Ah @12V | Cost |
|---|---|---|
| 7 Kwh | =7000/12 =583 Ah | $3,000 US |
| 10 Kwh | =10000/12 =833 Ah | $3,500 US |
Jehu's Power Wall
| Spec | Details |
|---|---|
| Capacity | 4.4Kwh |
| Ah @12V | 366 Ah |
| #cells | 600 |
| Cell | 18650 |
References
| Reference | URL |
|---|---|
| Buying Used Batteries | https://batteryhookup.com/ |
| Battery Pack Calculator | http://repackr.com/ |