Part of our Yaesu FTX-1: The Complete Guide.
Yaesu’s spec sheet gives you a duty-cycle number for the internal battery, but that’s not the same as what you’ll actually see keying up on SSB or grinding through FT8 for an afternoon. Here’s what I’ve actually measured and how I plan around it.
What the internal battery actually gets you
The Field Head’s internal battery is rated for several hours of SSB use based on a typical duty cycle, but that number assumes normal ragchew transmit-to-receive ratios. Digital modes like FT8 have a much higher effective duty cycle since you’re transmitting on a strict, frequent schedule, so you’ll burn through the battery meaningfully faster than the SSB number suggests. In practice, I plan for shorter sessions on internal battery alone if I know I’m running FT8 rather than voice.
Extending runtime with external power
For anything longer than a couple hours, I run the Field Head off my DIY 100Ah LiFePO4 battery box rather than the internal cell. This also unlocks the higher external-power output level rather than being capped at the lower internal-battery QRP setting, which matters if conditions are marginal and you want a few extra watts without switching to the full Optima setup.
Charging habits that actually matter
USB-C charging is convenient, but I don’t rely on topping off from a power bank mid-activation as a real strategy, it’s slow relative to draw under transmit load. I charge the internal battery fully at home before any trip and treat USB-C charging in the field as an emergency trickle, not a plan.
Rough planning numbers I use
- Short activation, under two hours, mixed SSB: internal battery alone, no issue.
- Anything longer, or any significant FT8 time: bring the LiFePO4 box.
- Full day out or EmComm exercise: LiFePO4 box is not optional, and I bring a way to recharge it too, whether that’s a portable solar panel or a vehicle connection.
- Cold weather cuts runtime noticeably on lithium cells, plan shorter sessions or bring backup power in winter.
None of this is complicated once you’ve done it a few times, but it took me one activation cutting short unexpectedly to start taking runtime planning seriously instead of assuming the spec sheet number would just work out.