Battery runtime
For field day, an activation or a power cut: how many hours the battery lasts with your ratio of transmitting to listening.
Battery runtime
How long the battery lasts on air. Most of the time you're listening, so receive current often counts more than transmit current. A net with lots of listening comes to five to ten percent transmit time, FT8 running continuously to half.
How the page calculates
- mean current = I transmit · share + I receive · (1 − share)
- usable = capacity · 0.9 (LiFePO4), 0.8 (Li-ion), 0.5 (lead-acid)
- Run time = usable / mean current
Only part of the rated capacity is usable: lead-acid hates deep discharge, LiFePO4 copes with almost anything. So the page uses 90 % for LiFePO4, 80 % for Li-ion and 50 % for lead-acid.
The capacity on a lead-acid battery's label usually applies to a 20-hour discharge. At high transmit current it gives noticeably less; the page doesn't calculate that, it only points it out.