Why is it that Tadiran Lithium Thionyl Chloride ( Li/SOCl₂ ) Cells can last decades, while other batteries only last months, sometimes even days? It comes down to a number of factors. The type of application the cell is in, the build quality of the cell and perhaps most important is the battery discharge rate.
Although Tadiran cells may look the same as any other battery, the old adage of “whats on the inside counts” really does make a difference when comparing them with something like Alkaline.
Lithium cells have a much higher power compared with Alkaline and will therefore last longer in applications. Even compared to other lithium technology, Tadiran cells have the highest capacity by weight and volume.
To calculate the energy of a battery we use the following: Capacity(Ah) x Voltage(V) = Watt Hours (Wh)
|Tadrian Li/SOCl₂ (3.6V)||2.4Ah x 3.6V = 8.64Wh||8.5Ah x 3.6V= 30.6Wh||19.0Ah x 3.6= 68.4Wh|
|Spiral Bound Li/SOCl₂ (3.6V)||–||5.5Ah x 3.6V= 19.8Wh||13.0Ah x 3.6V= 39.0Wh|
|Lithium Manganese (3V)||2.0Ah x 3.0V= 6.0Wh||–||–|
|Alkaline (1.5V)||2.6Ah x 1.5V= 3.9Wh||8.5Ah x 1.5V= 12.75Wh||15.0Ah x 1.5V= 22.5Wh|
Although the numbers show that Tadiran cells hold the largest Power, it’s how they deliver the power that makes them able to last decades in their suited applications.
Theoretically a Tadiran AA cell rated at 2.4Ah can draw 2.4 Amps of current for 1 hour, 0.24Amps for 10 hours, or 0.024Amps for 100 hours. However in reality, the amount of current that can be pulled from a battery is limited. Think of it as a 1 litre bottle of water. When you try to empty it, it is almost impossible to get the full litre out instantly. Instead the amount of water that leaves the bottle is determined by the size of the opening. (see diagram to the right)
Different cells are manufactured to perform in different scenarios. Spiral-bound Lithium Thionyl Chloride (Saft LSH range), Alkaline or Lithium Magnesium Dioxide are classed as high-rate cells and are great at delivering large amounts of power over short periods of time. Keeping with the same analogy, they are a bottle with a larger opening that can deliver more water quicker.
Tadiran cells on the other hand have smaller openings. Delivering Medium to Low flow rates over long periods of time. They are more are suited to applications where average current discharge is measured in micro amps. In such devices they have been known to operate for 40 years.
When it comes to powering applications for such a long period of time, self discharge becomes another important factor to consider. The lower the battery self discharges, the longer it will perform. It is in this field where Tadiran cells really shine.
All batteries discharge over time. To better understand battery discharge we can again use the bottle analogy. Tadiran Lithium Thionyl Chloride cells have a smaller opening compared to other primary cells aka, they have lower flow rates than other chemistry. What this does however, is results in less evaporation / self discharge and a longer operation life.
Within the Tadiran Range they even have an Extended Operating Life Series (XOL). Some High Rate Cells lose 10% of their volume each year, the XOL series lose just 0.7% per year, resulting in 86% volume even after 20 years of self-discharge.
For applications that require a long operational life with pulses of high power; A Tadiran cell paired with a Tadiran Hybrid Layer Capacitor may be a good option.
If you need more information about Tadiran cells, and whether Lithium Thionyl Chloride is suitable for your application, contact one of our friendly team who will be more than happy to help.