Maximum allowed voltage for SL3Pro? Type of rechargeable lithium batteries?

What is the maximum voltage allowed for the Nuki 3.0 Pro? Can I use „real“ 3.7v li-ions which would have 4.2v per cell when fully charged x 4 = 16.8 volts? The recommended lithium batteries from your help page have apparently 1.8 volt and are not rechargeable. I wonder if I’d have to use a modified battery case with 2 serial / 2 parallel regular li-ions that would serve 8.4 volts max, or what the real max voltage supported by the electronics is without burning the device.

Background: I use several SL3 Pros and one is installed at a garage door where I think the NIMH batteries of the included power pack will be a problem during cold winter temperatures (assume the very limited supported temperature range to min 10 degrees celsius comes from the batteries). Li-Ions handle cold temperatures better but I want to use rechargeable batteries and if needed might add an external self-made battery case if I cannot fit what‘s required into the provided case (does not need to be the prettiest solution in the garage).

Would be great if someone could provide more insights. I also wonder how exactly the battery percentage calculations work depending on what battery type is selected (might be the next problem?)

Thank you!

AA batteries can have slightly above 1,5V. Everything up to ~7V will work.

Unregulated and -controlled Lithium cells in 14500 format will break the Smart Lock and are no good idea anyways …

There are regulated lithium cells in AA format available which are usually rechargeable via USB (search for “aa lithium usb”). They might work, but could have problems with high currents (e.g. when the door is stiff or while unlatching) because the included electronics usually also limit the maximum current (3A would be ideal, 2A should work in most cases too).

Based on voltage, which means it won’t work for any other cells than the ones that are officially supported. Also the regulated lithium cells mentioned above will always show 100% as long as the electronics do not artificially cause a drop in output voltage based on an internal fuel gauge (which - as far as i know - they do not do).

Hello Jürgen. Got it. I will probably just put a power outlet next to the door to permanently use a power supply then in the garage.
Thank you very much for the very quick reply and insights provided!

Or you just try it out with the Nuki Power Pack. If the batteries really become too weak or die off too early, you can still power them permanently (the power pack is made for that use case).

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