MultiNav Pro+ GNSS 18Hz rate + BLE streaming - can the power kit keep up?

Ran a pretty similar setup a while back - 18Hz GNSS plus continuous BLE is definitely on the heavier end of the sustained draw spectrum for the power kit, but in my experience the super-cap holds up fine as long as you're not also running something like a display or heavy sensor polling on top of it. The thing to watch out for is the input source side - if your charging path can't replenish fast enough between BLE TX bursts you'll see the cap voltage sag over time and that's when you get the brownouts. Might be worth logging your rail voltage in the field for the first few runs just to see where it actually sits under real load before you commit to the design.

@Richard Martinez the 24-hour runtime spec on the power kit is rated for the full module stack, so 18Hz GNSS plus continuous BLE TX is well within what it's designed to handle — you're not pushing into territory that should cause brownouts under normal conditions. That said, the previous reply nailed the real thing to watch: it's the charge replenishment rate that matters most in a mobile deployment, not the cap capacity itself. If your input source (solar, vehicle 12V, whatever you're using in the field) has any intermittency, that's where you'd see rail sag accumulate over a long session. Logging your supply voltage for the first field run is genuinely good advice — I'd add watching for any correlation between BLE TX bursts and voltage dips specifically, since that's usually the first symptom before a brownout actually hits.

Richard Williams nailed it on the input side being the weak link - I'd add that if you're seeing sag it's worth checking whether your charging source has any current limiting kicking in, because some of the common input configs will throttle earlier than you'd expect under that kind of sustained combo load. Throwing a small ceramic cap right at the module's power pins helped stabilise things for me on a similar build, just takes the edge off the BLE TX spikes before they propagate back to the supercap rail.

Both Richards have covered the main failure modes well - one thing I'd add from my own field testing is that thermal conditions matter more than you'd think with this load combo, the supercap's effective capacitance can drop noticeably when it gets warm sitting in a enclosure in the sun, so if you're right on the margin on the bench you might find yourself with less headroom than expected outdoors. Definitely log that rail voltage like Richard W suggested, even just a quick voltage divider into an ADC pin gives you enough visibility to catch a slow sag before it becomes a problem.

One more thing worth adding to what everyone's said - if you haven't already, check whether your firmware is actually holding BLE TX on continuously or if there's any natural gap between packets you can exploit, because even shaving the duty cycle a little can make a real difference to the average draw and give the supercap more breathing room. 18Hz GNSS is the fixed cost but BLE connection intervals are sometimes more tunable than people realise depending on your stack config.

James makes a good point on the BLE side - I'd actually combine both angles and log rail voltage *and* dump your BLE connection interval params at the same time, that way if you do see sag you can correlate it against actual TX duty cycle and know whether you're fighting a firmware tuning problem or a genuine power budget problem. Saved me a lot of head scratching on a previous build where I assumed the stack defaults were sensible and they really weren't.

Joseph's point on correlating those two logs is solid - I'd also throw in a timestamp on any GNSS fix drops you see, because in my experience the brownout doesn't always kill the rail cleanly, sometimes the GNSS module just starts missing fixes quietly before anything else falls over and that's actually your earliest warning sign.

Really good shout from Richard A on the GNSS fix drops being an early warning - I'd actually tie that together with Joseph's logging suggestion and just have your firmware spit out a simple counter of consecutive fix failures alongside the rail voltage, that way you get a single log stream that tells the whole story without having to correlate two separate files after the fact. Took me an embarrassing amount of time on a previous build to realise the module was quietly struggling before anything else showed a problem.