We have some inexpensive smart locks at one of our office locations, wifi enabled Ultraloqs.  The documentation states to use alkaline batteries only, but replacing them can get expensive over time.  We also use a lot of wireless devices that run on AAs and AAAs, same problem.  We go through a significant amount of cash on alkaline batteries.  I am trying to determine if there is a suitable rechargeable AA and AAA that will work for us.

Ultraloq's documentation says to not use rechargeable batteries and, as is typical, they assume I am a stupid Neanderthal and can't comprehend the power requirements and what different kinds of batteries will deliver, so they just make the blanket statement without providing any detail.  Instead of accepting that, I thought I'd consult with the font of wisdom .  I am of a mind, from what I've read, that lithium ion AAs will probably work in the smart locks with caveats.  They're probably well suited to things like wireless mice, but our people travel a lot and I don't want to create airport hassles with lithium ion batteries either.  Here's what my research has told me thus far...

Rechargeable AAs basically come in two flavors.  Nickel Metal Hydride and Lithium Ion.  Well, and Nickel-Cadmium but I don't think those are being made anymore.  NIMH has the advantage of being able to provide large burst current (camera flash, for instance.  Might also apply to an electrically operated smart lock).  Often times NIMH has even more capacity than traditional alkaline (this will depend on the quality of the NIMH battery, and they are not all created equal).  NIMH also provides a smoother voltage curve, ie, as alkaline batteries discharge, the voltage starts dropping off immediately and steadily declines until insufficient voltage is being supplied to operate the device in question.  That curve for NIMH is shallower, especially at the beginning when fully charged.  The downsides of NIMH are that they self discharge (though the new low-self discharge types mitigate this a lot) and they also only start out at supplying 1.2v as opposed to the typical 1.5v you get with alkaline or lithium ion.  NIMH can also develop a memory and so will need a charger that can condition them over the long term (they are less susceptible to this than the old NiCD batteries, but it's still a thing).

The advantages of lithium ion are very constant current until the batteries go dead, in which case they go dead rapidly.  They also supply the rated 1.5v and generally supply "clean" electricity, which is good for sensitive electronics.  Due to the fact that lithium ion batteries tend to be a bit burny/explodey they usually have protection circuits to cut power if too much draw is detected.  That could be a problem in a smart lock for locking/unlocking, but I don't know this for certain.  They also have almost no self discharge issues.  The downside is that when they go dead, they go dead very rapidly without much warning.

First, dealing with the smart locks.  Lithium ion seems like the better choice if they can supply the amount of burst power needed to operate the physical lock and won't, in some manner, damage the electronics.  So first question is towards the smart locks, has anyone gone against advice and used rechargeable lithium ion in these, and how well did it work?  For that matter, has anyone used the lower voltage NIMH batteries successfully?

Second, wireless mice / keyboards and similar.  Lithium Ion might seem right since we are talking at least somewhat sensitive electronics and lithium ion will deliver clean current.  Downside, I don't want to create airport problems for our employees when they travel.  I know they let people on planes with lithium ion batteries in laptops and cell phones, but I've long suspected they do that as a practical concession, since all of these devices use lithium ion batteries.  That pushes me more towards NIMH for these devices, but I question how often they'll need to changed / recharged due to the self discharge issues and if the 1.2v current they provide will be an issue.

Looking for any and all input.

Enloop, latest generation, made in Japan.  Not cheap, but they are the best.   Honestly, you could probably get away with any brand.   I’ve been using every type for 20 years, and I don’t think I’ve ever seen one leak.   Get a good quality smart charger.

Panasonic Eneloop Pro

+3 Eneloops are what you seek. They will save you a lot of money in the long run. Get some solar chargers (or genny) and they're useful in grid-down situations, too.

Project Farm has done numerous tests on AA batteries.  I tend to use Amazon batteries after watching his stuff as I use a LOT of rechargeable batteries in LED lights around the house and yard.