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A snapshot of the state of development towards Bristlemouth power delivery created September 30, 2025. Also an overview of paths forward to achieve the v2 spec.

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Current State

• The v1 specification for Bristlemouth power delivery and consumption is that individual Bristlemouth modules should not consume more than 12W of power from a nominally 24V bus, and must operate at bus voltages between 16 and 32V.
• The draft v2 specification pushes the delivery rating to 250W max power.

Within the v1 specification, there are several relevant details to consider:

1. What is the power source, and what is its maximum output capability?

• The only off-the-shelf commercially available Bristlemouth power source today is the Sofar Spotter, which is capable of delivering a maximum (peak or continuous) of 6W to the Bristlemouth bus at 24V.
• However, it is simple for developers to create their own Bristlemouth power sources by connecting any standard 24V DC power source into the network via a PoDL LISN (Power over Data Line Line Impedance Stabilization Network) [see the Sofar Mote reference design for example implementation]. Care must be taken not to exceed the maximum through-power for modules in the connected network when doing this.

2. What is the maximum interface power?

• The maximum current rating of the Bristlemouth connector interface has not been well-characterized, but it has been comfortable tested up to 10A continuous and the true rating likely significantly exceeds this. At a 10A current, the 16AWG hookup wires and PCB traces would be the limiting factor.

• The commercially available Sofar Bristlemouth Mote has an absolute maximum Bristlemouth current rating of 890mA, limited by the PoDL inductors. This results in an absolute maximum power through a Mote or to a connected load is 20W. A future revision of the Mote in Q4 2025 increases this rating to 32W.

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  Note: The Mote does not have internal circuit protections to limit through-current. If this current limit is exceeded, it will permanently damage the Mote.

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Current Development

Two R&D projects have explored advancing the power delivery capability of Bristlemouth.

Bristlemouth Jetpack

This project was part of a Bristlemouth Development Hackathon in 2024. The team created an external daughterboard for the OTS Bristlemouth Mote, which contained much higher current-rated PoDL components. Standard Mote PCBAs were manually modified to bypass the on-board PoDL circuitry, and to instead use the PoDLs on the Jetpack.

The prototype was tested to 100W power delivery, including on highly inductive loads such as motors.

The open source prototype Bristlemouth Jetpack designs are included below in the references.

High Powered Bristlemouth Dev Kit

In collaboration with the University of Pittsburg on the ARPA-E SEA-CO2 program, Sofar is developing a high-powered Bristlemouth Development Kit that includes a point-of-load battery solution. A Li-ion battery internal to the Dev Kit charges from connected low power systems (such as the Sofar Spotter) when excess energy is available, then delivers the stored energy to locally connected high power loads on demand.

The current version of this system was designed and tested for loads in the ~50W range, but the design is in principle extensible to 100s or even 1,000s of Watts of peak power delivery. Prototype User Guide and reference source files are included below.