Digital lock batteries and related questions

What batteries to use? What to do if the batteries run out of juice? These are the two most commonly asked questions by new buyers and also existing users.

Here are simple practical answers for batteries for digital locks:

1. What batteries type to use?
   
   Use 4 x AA-size alkaline batteries. Sometimes the lock allows up to 8 pieces (when the lock is equipped with remote control or bluetooth option. If your lock can work with 4 pieces then stay with 4 pieces. Risk of battery leaks are lower with fewer batteries so don't put more than required.
   
   You do not need the more expensive lithium batteries because the locks do not discharge high currents like your flashlight, cameras and other high speed motorised gadgets. You should not use rechargeable batteries (because manufacturer says so).
   
   
2. What brand of batteries?
   
   We are not intimately familiar with each battery brand and the supply chain. We can however put on our thinking hats and rationalise along the following lines to minimise chances of battery leaks:
   - buy from high traffic​ outlets (supermarkets, petrol kiosks) on the assumption that the batteries have not been on the shelf for a long time (alternatively you can try interpreting the dates on the batteries)
   - buy normally priced batteries and avoid heavily discounted batteries or batteries priced very low
   
   We think Energizer Max at NTUC supermarket could be decent brand to use. Avoid Eveready, IKEA and GP batteries.
   
   
3. What if the batteries run out of juice?
   
   Fear not as this has been a design consideration since the first iteration of digital locks from many years ago. When the battery is low (and requires replacement within the week), the lock will play a melody and there is also a visual indicator. In the event you miss all these indicators (say when you are away on vacation), and the batteries are completely depleted, just get a 9V battery from the supermarket and plug it in from the outside to give it enough power for you to unlock using one of the access methods (pin etc.).
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Hummingbird

See pictures below for AA size and 9V Energizer Max alkaline batteries.
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