Alkaline 12V A27 Battery
A27 battery is standard, non-rechargeable, cylindrical battery, featuring a nominal voltage of 12 volts and is commonly used in remote controls, telecommunication devices, security systems, and similar.
A27 battery is its most common name, but this battery is also known as 27A, A27BP, 8LR732, G27A, GP27A, L828, MN27, etc. battery.
A27 Battery - Features and Specifications
A27 battery features physical dimensions of (diameter x height) of 8.0 x 28.2 mm (~0.315 x 1.110 inches) and it usually weighs 4-4.6 grams.
Nominal capacity differs from model to model, but it is mostly declared to be around 20-25 mAh - actual capacity depends on the discharge conditions and temperature and the cutoff voltage of the powered device.
Internally, the A27 battery consists of eight (8) alkaline LR732 batteries connected in series, hence 12 volts.
Note: alkaline LR732 batteries are rarely used independently.
Cutoff voltage depends on the powered device and is between 6.0 and 8.4 volts with most devices having a cutoff voltage of 7.2 volts.
Although A27 battery is not the most common cylindrical battery, it is being manufactured by many brands, that often use their own labels to identify this battery, hence so many labels for this battery size: 27A battery, A27BP battery, 8LR732 battery, G27A battery, GP27A battery, L828 battery, MN27 battery, etc.
But, they all use its standard label - 'A27 Battery'.
A27 vs A23 Battery
A27 and A23 are very similar 12 volts batteries, both internally consisting of 8 alkaline, non-rechargeable batteries, connected in series.
A23 battery is somewhat larger, with physical dimensions of (D x H) 10.3 x 28.5 mm (0.406 x 1.122 inches). Due to the larger volume, the A23 battery also features a larger capacity (50-60 mAh vs 20-25 mAh).
Some devices that are powered by A23 batteries also feature a plastic battery holder, allowing the A27 battery to be placed in the battery compartment and be used instead of A23 battery.
Due to the larger capacity of the A23 battery, personally, the A27 batteries should be used instead of A23 batteries only when there are no A23 batteries available.
Long Story Short: A27 battery may easily be found at local hardware stores or online shops.
Although A27 batteries from reputable brands feature shelf life of 3-5 years, it is recommended to check the manufacturing date of the batteries, if possible.