Battery and safety

You are able to start a dive with a low battery, however you are alerted if it is below a specific threshold (At the moment that threshold is 10%). Low battery behavior is specifically one item I tested while the device was in beta. In my experience, even 4% battery life was enough to provide for a 60+ minute dive. I never attempted a dive with a lower charge than that. In addition to the alert, the battery charge remaining is included on one of the dive information screens for review while in a dive.

I understand the concern for battery life, however I'm not sure that a larger battery is required. It was simply never an issue for me. Battery life is advertised as having 10+ days. I regularly surpass 2 weeks with no problems. I've also had it last a full week long dive trip without requiring a charge. Without forethought, low battery conditions will happen; regardless of battery capacity.

Battery was an issue with Fenix 3 that it usually lived less that the advertised time. But with Fenix 5 series and later I can easily get more battery time that advertised two weeks. So I think they actually decreased the advertised times to fit more to the real timing. So it shouldn't be hard to surpass the advertised two weeks in daily use. However, usage in activities may be more. My 5X have never reached its advertised 20 hours GPS activity.

Just a quick note of an above edit: I erroneously mentioned the threshold was 20%. After looking back at my notes I've determined that it's actually 10%.

Thanks rjanuary, for the comment. If I understood you well, did you have the chance to test MK1? if yes, can you share the impressions and/or photo?

This is not really any different from dive computers that have non-rechargeable batteries - most will warn you but not stop you. Worst that happens is it runs out of battery and you have to cut your dive short and make a controlled ascent on your gauges (and hopefully your watch for timing safety stops :) )