What do SOC, SOH, IMD and IMR mean for a lithium battery?

There are essential terms to know when it comes to lithium batteries. They may seem a bit harsh but they are quite simple to learn as you will see.

Among great classics, there is the SOC which signifies “State of Charge”. It is the battery’s state of charge in percentage. The value evolves between 0 to 100 %. The state of charge is calculated with various parameters:

• The first parameter is the battery’s coulometric statement in charge and discharge. Thus, we will permanently measure the electrons moving inside the battery with its BMS and PDU.
• The second parameter is the SOC/OCV table of the battery’s cells.

Here is another term: the SOH, which means the battery’s State of Health. A battery in healthy condition has a 100 % SOH at the beginning of its lifetime.

We permanently measure several battery parameters in real time in order to obtain an accurate calculation:

• The temperature,
• The current,
• The number of cycles.

There are many complex algorithms of the BMS’ internal code which allow to obtain a measurement accuracy inferior to 5 %.

IMD and IMR are not as widely known parameters but they remain essential in order to manage your lithium battery’s power in charge and discharge mode:

• IMD signifies “maximum discharge current”,
• IMR signifies “maximum recharge current”.

If we use the example of an electric vehicle, IMD and IMR are up to 100 % for a standard use. If there is a high temperature, the percentage will decrease in order to limit the vehicle’s discharge and charge power. This data will be sent to the vehicle’s calculator through the CAN bus. The vehicle will be required to lower its discharge and charge power in order to avoid the battery deterioration.

At TYVA Energie, SOC, SOH, IMD and IMR values are sent in real time through our BMS’ CAN communication bus in order to get these parameters in real time.

Thank you for your attention, see you next week for a new video.