Watch out for "equivalent" batteries; they are not all equivalents.
The SAFT LS14500 has a current discharge rate of 130mA. The LST-14500 has only 45mA. The LS-14500C has only 25mA. Maplin sells a Maxell ER6-C which is a 3.6v AA battery and list it as an equivalent (Maplin > ER6C Lithium Cell) but this has a current discharge of 100uA. Selecting the wrong one will cause problems. Only use the correct battery as indicated by the manufacturer unless you are sure of the equivalency. Some functions of the handset can pull a large amount of current, such as the alarm screen indication which can exceed the maximum recommended continuous current of the wrong cell.
In addition to the electrical performance and characteristics of the cells, the SAFT has additional qualities that put it on our "approved list"; Stainless steel container and end caps (low magnetic signature) Hermetic glass-to-metal sealing Non-flammable electrolyte Low self-discharge rate Compliant with EN 50020 intrinsic safety standard
We have spent a lot of time in testing a number of cells in our products and only recommend the LS-14500.
We hope this helps users to understand the reason this manufacturer has chosen their power supply.
we try to hold stock of all products, but if showing out of stock there may be a few days wait while new stock arrives.