One device or two? (66i only vs InReach Mini plus 66st)

I'm not sure how significant the battery life difference is between the 66 series (st and friends) and the 66i. The best info I can find says the 66 (presumably including the st) gets up to 16 hours normal use, 170 hours expedition mode. Vs. 35 hours normal, 200 hours expedition for the 66i. I know 35 vs 16 sounds like a large difference, but Garmin does not cite the battery capacity used for those "up to" numbers for the 66. For example, you might get better results with a higher capacity set of NiMH rechargeables. Or not.

One large difference here is that you can carry spare batteries for the 66st. Both the Mini and the 66i use a built-in rechargeable battery which cannot be swapped. For the 66st, you would presumably consider just carrying a few sets of spare batteries, rather than lugging a power pack. Not an option with the 66i or Mini.

Purely anecdotally (based on what I've seen on the forums and my own non-systematic testing), I would expect the 66i to handle a 3-day trip with your cited use case. You do need to keep it  sleeping in expedition mode as much as possible. When you do wake the unit, you would need to be careful to allow it to complete all inReach communication (potentially including an active message check) with a clear view of the sky. The unit will not sleep if there is something on the inReach queue. So blindly carrying on after waking it in challenging reception conditions can deplete the battery unexpectedly quickly.

If you were using the 66st instead, I'm not sure why you would not use the 66st in expedition or battery saving mode? That would put the 66st (170 hours) on a much closer footing with the 66i (200 hours) in your comparison.

Also note that all battery chemistries exhibit variations in capacity based on temperature. Particularly if you plan to hike in cold weather, stated capacity/lifetime may well be (quite a bit) too high.

All of that said, you should not take anybody's word for battery life in a safety-oriented device. Once you've made up your mind, be sure to test the lifetime in real-world conditions before relying on it in the back country. Note that stationary testing does not yield realistic results.

Excellent point about the 66st having expedition mode also

66i battery = 9.3 watt-hours (unconfirmed but seems close)

2x Lithium AA batteries = 8.4 watt-hours

But, the 66i is busier with Iridium communications so, practically speaking, I'm calling this a wash on run time - I updated the advantages lists in the original post

I'll add that I normally carry a power back anyway. I have rechargeable lights, ham radio, and a few other gadgets I normally carry. I have different capacity packs to choose based on trip length, temperature, and planned activities (I've sort of "standardized" on USB-rechargeable devices). However, all else being equal, I do understand that adding another device (or 2) would require either additional capacity (weight) or additional batteries (also weight). I only bring this up to indicate that the prospect of carrying a power pack is already considered so I didn't add this as a pro / con. Extra AA batteries vs. incrementally more capacity in a power pack seems like mostly a wash to me.

Thanks for the input - keep it coming

I took my 66i on a 5-day/4-night trip, had it tracking on 10min intervals probably 4-5 hours a day, normal GPS mode, maybe a couple dozen messages total, and still had battery life left over at the end.

That's great to hear. A day (maybe 2) better than I was expecting but in line with what Garmin publishes.

I wonder if a single set of AA Lithiums would have driven a 66st that long (?)

I'm facing the same dilemma.

As well as a desire to possibly save an inReach (Mini) batteries for emergency, I have data privacy concerns with the 66i. Apparently one will be forced to sync all tracks and waypoints to Garmin Explore. The younger crowd may not mind this but I do, even if I don't have a special waypoint of "buried treasure". I want control of what I send to the cloud but that seems to be missing. (see my other post on this topic). 

On the other hand, I expect the 66i screen and usability for SOS communication may be better than the Mini for my 55-year old eyes. (Yes, you can pair a phone with the Mini but I prefer to not rely on that.)

Good luck!

I have read your other posts and agree. In the area of pros and cons, I thing you just identified another pro for the 2-device approach. Namely: With 2 devices, you can turn off the Mini until such time as you want to use it, giving you months of battery life (if you choose to run it that way).

At one point, I was looking at the combination of the 66st and the InReach Explorer+ (bigger screen) but decided if i was going to carry 2 devices, that I could live with the relatively shorter battery life of the Mini in order to reduce my load. Maybe the Explorer is a consideration for you?

Thanks for joining the conversation and giving me another point to consider.

The Mini is going to sync in the same way as the 66i. However, instead of the Explore app and/or a wired sync, the Mini still uses the older Earthmate app and/or wired sync. You will not escape the sync requirement on any iR device. The only way around it is to simply refrain from syncing. But you can only do that for so long - then there'll be a f/w upgrade. Those get delivered via Garmin Express - and I've never been sure how much data it syncs, or with what it syncs. But it also syncs.

Just my opinion. But I would not consider a legacy device like the Explorer+ unless battery life is absolutely paramount. The Explorer+ is not a full member of the Garmin ecosystem. It still uses maps in the old DeLorme format, which limits your choices. it also lacks the ability to connect the device as a removable USB "drive" - so sync is the only way to get data on or off the device.

The Mini is also sort of stuck in the middle. It uses the older Earthmate app to sync, but gets f/w updates via Garmin Express.

The 66i is the first iR device which is really a true member of the Garmin ecosystem.

twolpert said:

The Mini is also sort of stuck in the middle. It uses the older Earthmate app to sync, but gets f/w updates via Garmin Express.

The 66i is the first iR device which is really a true member of the Garmin ecosystem.

That's a distinction I missed. I appreciate you pointing it out. More to think about.

You know, if there was only one satellite communicator and only one handheld GPS unit, then these decisions would sure be a lot easier.