IZ2 Critical Failure

Tech Note: TN0983
Product: IZ2, IZ2H, LZ48
Version: All
Date Added: 2016-12-05


We discovered a failure mode in the IZ2 electrical stimulator / LZ48 battery pack that can lead to improper device output. Although the failure occurrence is relatively rare, this failure mode can result in the unintended delivery of high current to the research subject and thereby potentially cause injury or death. As such, we are taking every step possible to address the issue and ensure the best possible safety for your research subjects.

We strongly recommend that you verify proper device operation prior to connecting any research subjects and initiating any stimulation protocols. If an LZ48 battery is fully discharged while still connected to the IZ2, under some operating conditions electrical components in the IZ2 stimulator can be damaged. After the failure of these electrical components, higher than intended stimulation current can be delivered to the research subject during subsequent device operation. In this condition, IZ2 devices must be returned to TDT for repair or replacement of the damaged components.


  1. To minimize risk, never allow the LZ48 battery to fully discharge. When the battery charge indicator is getting low, stop the experiment, disconnect the subject, and recharge before further use.

  2. Always verify proper operation of your device before connecting to a research subject. If you observe red LED status lights on your IZ2 during setup, do not connect a research subject or proceed with the experiment. Please see the IZ2 Operation Guide for additional details. If you encounter any problems or need help verifying proper device operation, please contact TDT Technical Support for assistance.

  3. Contact TDT for a free LZ48PC protection cable. This new cable will monitor line voltages and protect the IZ2 from electrical component damage even if the battery is inadvertently allowed to fully discharge. The cable will replace the LZ48 to IZ2 cable that shipped with your device and can be easily installed in a matter of seconds.

  4. Consider upgrading your current LZ48 battery to a newer LZ48M battery pack that includes several additional protections and safety features including medical grade isolation from mains power when charging.