#testdata

FAQ: Voltage level for the LTO cells

Question: Concerning the LTO cells, I can see that some information mentions the nominal voltage at 2.3V some other datasheets say 2.4V. I wonder what is the nominal voltage of the 5-cell pack: 11.5V or 12V?

Answer:  both versions of the information are correct. The reason is that the discharge voltage of the LTO cell is between 2.45V to 2.0V. The charge voltage of a single cell is between 2.15V to 2.8V. (valid for 1C rate and 25°C)

This means that the voltage of the 5-cell pack is from 12.25V to 10V. The charge voltage of the pack is 14V.

See more here: 

FAQ: Determining the number of cells for a battery pack

The safe battery technology LTO - - - - only 95°C during the short circuit

The data recorded at the short circuit test show that the maximal temperature of the Lithium Titanium Oxide - LTO-40AH - cell reached to some 94°C.

This tests proves that the lithium titanite(LTO) batteries are very safe and even during a massive short circuit, the temperature stays within the safety limit.

Check the safe LTO cells at GWL/Power web.

Dogma: The energy of the regular “AA” cells = 1.43Wh

The AA cells are the primary one-time use cells. The nominal voltage of the AA cells is 1.5V and their capacity in Ah usually not stated in the specification. It shows that people are fooled easily. 😮

Image: you buy the milk in some box every day, but you never now how much liters or milliliters you actually buy. Sometimes more, sometimes less. Yet, with the AA cells and other types of household products most people buy these as a black box with no technical specifications. We really wonder how is this possible.🙃🙃🙃

Most of the producers do not give any specific discharge curves and the technical data is very difficult to find. The image above shows an example from the official data provided by Duracell for the Procell Alcaline Battery.

Unlike the lithium (LFP) cells, the performance of the AA cells is influenced by the current of the load. This type of battery has a higher inner resistance and when you use more current --- a part of the energy will be turned into the heat and the cell will warm.  Generally said: these AA cells should be discharged slowly in a matter of days, weeks or months.

However, to compare the performance of various cells, there has been a standing testing procedure with the 500mA current from the full voltage (typically above 1.5V) till the discharge voltage of 0.8V.

There is a test comparison video that shows the results of the AA cells from various producers. With the 500mA test the capacity ranges from 1444 mAh to as low as 1167 mAh.  Check the video here.

As a result, you can see that with the AA cells, you actually buy some energy with no guarantee of how much you actually buy.

Based on these test, the average capacity of the AA cell is around 1300mA. With the cell voltage dropping between 1.4V and 0.8V the average voltage is considered to be 1.1V.

The typical energy of the AA cell (discharged at 500mA) is 1.1V x 1300 mAh = 1.43Wh.

Testing and working – Non-Stop!

What are you doing on the first spring Saturday in 2020?

Actually, the first spring Saturday in 2020 brought in a wave of cold weather to Europe. It was snowing today even in Prague.

However, the GWL/Team members keep working even on weekends, analyzing battery test data reports to make decisions about new and better products to be introduced to our customers, partners and friends.

Overcharge of the TSWB cell

The diagram shows the overcharge of the TSWB cell and the temperature increase.

The cell is overcharged (after already being fully charged) gradually to 5V, 6V and 8V per cell. The temperature is monitored. The temperature reaches some 130*C.

The total time of the test is 30 minutes. During the test the cell did not explode, did not start burning, did not set itself on fire.