One of the most common batteries used for internal Real Time Clock memory back up is the lithium 1/2 AA size cell.

The thing to realise about these little cells is that they can come in different colours and can be made by different manufacturers. They have a few things in common in that they are designated as 1/2 AA, that means the dimensions are typically 14.5 mm diameter and 25mm long. They are of Lithium Thionyl Chloride Technology. They are nominally 3.6v 850 mAh. Lithium Thionyl Chloride cells are actually 3.67v but are often described as anything from 3.5v to 3.7v.

We are a main distributor in the UK for Tadiran Lithium GMBH (used to be Sonnenschein Lithium )therefore we can offer a keen price on the standard sl350/s ( the little blue battery ) Note all Tadiran Lithium Batteries have now become purple in colour.

We can also offer most of the other alternatives subject to availability -- they usually work out a bit more expensive because they are not as commonly available.