Is lithium battery compatible with smart lock?
As long as they are AA and have 1,5V yes. Please make sure that you set the proper battery type in the Smart Locks administration. Otherwise you won’t get meaningful battery level reportings and battery warnings.
Hello, you say that lithium batteries are compatible with SL4 if they are 1.5 V but the original Nuki batteries are 1.2 V. How do you understand that?
Whether batteries have 1,2V or 1,5V does not make a difference. But many lithium batteries have 3V or more. If you insert those the Smart Lock will not function and might be permanently destroyed.
And I suppose that as long as they are 1.5 V they can be put with higher power, for example 3500 mAh, right?
“mAh” is not power, but capacity. This has no impact on the function of the Smart Lock. Just don’t get rechargeable ones, because everything that comes in AA format, is Lithium and rechargeable usually does not run on 1,5V but uses regulators to achieve this which are very often not able to provide enough energy to the Smart Lock in high drain situations (e.g. when pulling the latch).
So, what type of rechargeable battery do you recommend to improve the performance (usage time and reliability) of the original Nuki pack? Ni-Mh or Lithium-ion? How many mAh?
If you have a Nuki PowerPack with a 2.5Ah capacity printed on it, you have revision 1. There is a newer revision available with different cells and improved electronics. It has a 2.05Ah capacity printed on it but delivers more usable battery capacity in most scenarios. It’s available in the Nuki shop. All Smart Lock 4th gen Pro are shipped with it too.
If you do not want to use the PowerPack, the recommendation is to use Eneloop Pros: https://support.nuki.io/hc/en-us/articles/4407674566929-Smart-Lock-batteries