Solar power
Battery Pack 18650
Protected 3S lithium pack for DIN rail
A 3S Li-ion 18650 battery pack with a TI BQ77915 protector on board, for solar and backup-powered sites. Protection runs in hardware with no microcontroller and nothing to set up: the thresholds are fixed in the chip at the factory.
Available now. Online shop coming soon.
Overview
What it does
It pairs with the MPPT Charger, which reads the pack's temperature sensor and charges it at 1.0 A from the factory.
Use three matched 3.7 V Li-ion cells, not LiFePO4, and fit a fuse in the PACK+ lead. Packs can be connected in parallel at equal voltage, never in series.
Features
- 3 x 18650 Li-ion, 11.1 V nominal, 12.6 V full
- Cell over- and under-voltage, charge and discharge over-current, short-circuit, open-wire and temperature protection
- Passive cell balancing while charging
- On-board thermistor for the protector, and a second one brought out for the charger
- Faults clear on their own once the cause is gone
- 4-pin pack terminal and two JST XH outputs, all in parallel
Views
Renders
Specifications
Technical details
Figures from the schematic, the module datasheets and the documentation on GitHub.
Documentation| Cells | 3 x 18650 Li-ion, 3.6-3.7 V nominal, one cell per position |
|---|---|
| Voltage | 11.1 V nominal, 12.6 V full charge |
| Protector | TI BQ7791501, factory-set thresholds |
| Cell over-voltage | 4.25 V, 1 s delay |
| Cell under-voltage | 2.8 V, 1 s delay |
| Charge current | Up to 1.5 A (charge over-current trips at 2.0 A) |
| Continuous discharge | Up to 2.5 A (discharge over-current trips at 3.5 A, then 6.0 A) |
| Short circuit | 12 A, about 1 ms |
| Temperature limits | Charge 0 to 50 °C, discharge -20 to 70 °C |
| Open-wire detection | Both FETs off if a cell connection is lost |
| Cell balancing | About 10 mA per cell, while charging |
| Idle current | 8 µA typical |
| Outputs | Pack terminal rated 5 A; 2 x JST XH rated 3 A each |
| Mounting | 35 mm DIN rail enclosure, 118 x 78 x 45 mm |
Works with
Goes with
Charge with a CC/CV Li-ion charger set to 12.6 V, such as the MPPT Charger, at 1.5 A or less.
Software
What runs it
None. The protector works on its own, with no firmware to maintain.
Downloads
Schematic and documents
Schematic
PDF, Rev 0.01, 116 KB
Documentation
Hardware notes and setup, on docs.modbee.org