Power without a host computer
Use a 9-volt battery when the device only needs USB power and does not need a host computer.
Power, not data
Power COLDCARD without plugging it into a computer.
COLDPOWER turns a standard 9-volt battery into a USB power source. Use it to run COLDCARD or another low-power USB device when you want power, not data.
- Power source
- Standard 9V battery
- USB output
- 5V, 500mA max
- Data path
- No USB data
“When you link up to another computer, you’re linking up to every computer that that computer has ever linked up to.” — Dennis Miller
Short answer
What is COLDPOWER?
COLDPOWER is a self-powered USB adapter for COLDCARD users. It supplies USB power from a 9-volt battery, so the wallet can turn on without touching a computer USB data port. That keeps offline setup, verification, and signing workflows cleaner.
Why it helps
Keep power and data separate.
A computer USB port is not just a power outlet. It is also a data path. COLDPOWER makes the setup obvious: battery in, USB power out.
Fit COLDCARD offline workflows
Power COLDCARD during setup, address checks, MicroSD-based signing flows, and other offline routines.
Make the cable honest
With COLDPOWER in the middle, the cable has one job: deliver power. It is not pretending to be a general-purpose computer connection.
Setup flow
How do you use COLDPOWER?
Attach the battery, connect the USB cable, do the offline task, and unplug when finished. The point is not complexity; the point is removing the computer from the power path.
Basic use
- Attach a standard 9-volt battery to the COLDPOWER adapter.
- Connect the USB cable for the COLDCARD or other low-power device.
- Turn on or wake the device and confirm it is receiving power.
- Use the device for the offline task, such as a COLDCARD check or signing flow.
- Disconnect the battery when finished.
Why not just use a laptop USB port?
Sometimes a COLDCARD needs power, not a computer. Plugging into a laptop is convenient, but it also introduces an unnecessary host. COLDPOWER gives you a separate power source for the moments when separate is the point.
Who it is for
Who should use COLDPOWER?
Bitcoin self-custody users
People who want a simple no-data power option around their hardware wallet workflow.
COLDCARD owners
People using COLDCARD with MicroSD, watch-only wallets, QR workflows, or other air-gapped habits.
Security-minded gift buyers
A practical add-on for the cypherpunk, Bitcoin educator, or hardware wallet user in your life.
Comparison
How is COLDPOWER different from a USB data blocker?
A USB data blocker still assumes there is a USB host on the other side. COLDPOWER skips the host and supplies power from a 9-volt battery.
COLDPOWER
COLDPOWER provides its own battery power and avoids the computer USB host. Use it when you want a visibly separate power source for an air-gapped workflow.
Typical USB data blocker
A typical data blocker removes or blocks data pins while still using a USB host for power. That can be useful, but the device is still plugged into the host power source.
Security habit
When should you use COLDPOWER?
Use COLDPOWER when a low-power USB device needs power and the computer connection adds nothing. For COLDCARD users, that includes address checks, MicroSD-based signing, seed verification, firmware preparation, and other tasks where a computer connection is unnecessary.
Specs and compatibility
Battery-powered USB power, no data path.
| Product | COLDPOWER 9-volt battery to USB adapter |
|---|---|
| Primary use | Power COLDCARD and other low-power USB devices without a USB data connection |
| Input | Standard 9-volt battery |
| Output | 5 volts, 500 mA max current |
| Data | No USB data path |
| Made by | Coinkite, maker of COLDCARD, OPENDIME, SATSCARD, TAPSIGNER, SATSCHIP, and BLOCKCLOCK |
Gallery
COLDPOWER in hand.
Photos show the adapter, battery connection, and USB power setup.
FAQ
COLDPOWER questions
What is COLDPOWER?
COLDPOWER is a 9-volt battery to USB power adapter from Coinkite. It powers COLDCARD and other low-power USB devices without connecting them to a computer USB data port.
Why use COLDPOWER with a COLDCARD?
COLDPOWER keeps a COLDCARD workflow physically separated from computer USB data connections. It provides battery power for air-gapped signing, setup, and verification workflows.
Is COLDPOWER the same as a USB data blocker?
It serves a similar no-data purpose, but it is self-powered. Instead of passing USB power from a host computer, COLDPOWER supplies USB power from a 9-volt battery.
What current can COLDPOWER provide?
COLDPOWER is specified for 5 volts and 500 mA max current. It is for low-power USB devices.
Need power, not data?
Buy COLDPOWER from Coinkite.