Part of our FT-891: The Complete Guide.
The FT-891 has no internal battery, full stop, so every field session starts with a power plan. Here’s how I actually run it off my DIY 100Ah LiFePO4 battery box.
Real current draw
Yaesu rates the 891 at roughly 23A on transmit at full 100W and about 2A on receive. Those numbers matter more than they might seem, a battery that looks like plenty of capacity on paper drains faster than expected once you’re actually keying up repeatedly on SSB or grinding through a digital mode session with a near-constant transmit duty cycle.
Wiring it up properly
I run heavy enough gauge wire from the LiFePO4 box straight to the radio’s power leads, fused at both ends for the actual current draw at full power, not just a token fuse. A loose or undersized connection here is a classic cause of voltage sag under transmit that shows up as reduced power output or the radio folding back power it thinks it can’t support.
Planning runtime for a real session
For a POTA or SOTA activation running mostly SSB, the 100Ah box comfortably covers a full day even at full power, since actual transmit duty cycle in a ragchew or activation pace is well under 50 percent. If I know I’m running digital modes for an extended session, I plan tighter, the near-continuous transmit cycle of FT8 pulls harder than casual SSB. Dropping power output for battery-limited sessions is also a legitimate option, the 891 doesn’t need full 100W to make plenty of contacts.
What I actually pack
- The 100Ah LiFePO4 box for anything beyond a short session, no exceptions given the 891 has zero internal backup.
- Properly sized, fused wiring rated for the full 23A transmit draw, not just receive current.
- A rough mental budget for the day based on SSB versus digital mode plans.
- A way to recharge if it’s a multi-day trip, whether that’s solar or a vehicle connection.
None of this is complicated once you’ve internalized that the 891 is entirely dependent on whatever you bring with it. Plan the power the same way you’d plan the antenna, and the radio itself stops being the limiting factor. See my FT-891 field kit walkthrough for how this fits into the rest of what I carry.