Assumptions
18650 Battery Assumptions
| Specification | Value |
|---|---|
| Nominal Voltage | 3.7v |
| Max Voltage | 4.2v |
| Cutoff Voltage | 3.0v |
| Capacity | 2500mAh |
Configuration Options
3S (9V-12.6V)
Pros:
- Can charge it from the car
- Works with most chargers (solar and car chargers)
Cons:
- Would not get full capacity when using with an inverter. The inverter would shut off at 10.5v.
4S (12V-16.8V)
Pros:
- Would be able to use the full capacity of the battery when converting to AC.
Cons:
- Would need to step down the voltage to 12v which may introduce some losses.
- Could not charge it off of the car
Battery Pack
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" |
Other Possible Packs
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 |
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/ |