LoTek Coordination

Open hardware · LT-B

Cellar

A lithium iron phosphate battery module with a charge controller and a solar input. Every hub has one; in networks built for resilience, solar-powered Cellars run hubs and relays entirely off the grid.

Specifications

Chemistry
Lithium iron phosphate (LiFePO4)
Capacity
1.2 kWh usable (C3)
Output
48 V DC and 24 V DC
Solar input
Up to 400 W, MPPT charge controller
Runtime
About nine hours for a Gantry hub, three days for a Stoop
Monitoring
State of charge, input source and temperature, reported with every poll
Enclosure
Ventilated steel cabinet, IP55
Parts cost
About $520, or $760 with a 400 W panel

Notes

Cellars are not monitored as nodes in their own right. Their state is reported by the hub or relay they power, and shown on that node’s page.

Revision history

  1. Larger usable capacity, a cabinet that fits through a roof hatch and state-of-charge reporting to the coordination site.

  2. Became standard for every Gantry hub with the H4 revision. Added temperature cut-offs for winter roofs.

  3. Built for Las Mareas, where the network had to run when the grid did not. Lithium iron phosphate cells with a solar charge controller.