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)
| 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 |
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)
| 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 |
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 |
Battery Management System
3S 100A Li-ion Lithium 18650 BMS Battery Charger Protection Board with Balance
| Feature | Details |
|---|---|
| Large discharge current | 100A |
| Instantaneous discharge current | 150A |
| Charging voltage | 12.6V |
| Large charge current | 10A |
| Overcharge detection voltage | 4.28±0.05V |
| Overcharge protection delay | 0.5S |
| Overcharge release voltage | 4.08±0.1V |
| Power balance detection voltage | 4.20±0.05V |
| Power balance release voltage | 4.20±0.05V |
| Electricity balance current | 42±5mA |
| Over discharge detection voltage | 2.8±0.1V |
| Overdischarge detection delay | 0.1S |
| Over discharge release voltage | 3.0±0.1V |
| Overcurrent detection voltage | 150mV |
| Overcurrent detection delay | 9mS |
| Overcurrent protection current | 200±10A |
| Overcurrent protection release condition | Disconnect the load |
| Short circuit protection conditions | External load short circuit |
| Short circuit detection delay | 250uS |
| Main circuit conduction resistance | ≤25mΩ |
| Working current | ≤20uA |
| Sleep current (when battery is over) | ≤10uA |
| Size | 8.2x5.1cm/3.23x2.01inch |
Test Results of Batteries
Spreadsheet: 88af-18650.xls
References
| Reference | URL |
|---|---|
| Buying Used Batteries | https://batteryhookup.com/ |
| Battery Pack Calculator | http://repackr.com/ |