Multi-level protection

Multi-Level Protection

How is your installation configured to ensure the safety of your battery, vessel, and crew?


Our approach has been to design a series of protection levels to keep incidents from turning into major catastrophes.


Imagine you are on a boat in the English Channel. It is nighttime, commercial traffic is dense, and a storm is headed your way. You suddenly lose energy on board: no light, charts, radar, or autopilot. You can’t step away from the helm to see what the problem is. Your boat and crew are in serious danger.


This is perhaps an extreme example, but if your only protection is a fuse or circuit breaker, or if your EMS merely disconnects the load when the battery voltage is low, you could end up in life-threatening situations.


If you are serious about your safety and value your installation, you should think of ways to avoid such dangerous situations. One way is to receive an early warning that something is abnormal and have the time to correct the problem before it gets worse.


 A multi-level protection approach will put you on the right track


The Different Levels of Protection

We have defined the steps you or your EMS can take to stay within a safety zone according to six levels of protection. Level 6 is the one you never want to see activated, but it will protect you if all else fails.


This is how the levels of protection can be applied to an off-grid electrical installation:


1. A well designed, documented, and executed installation

This is the responsibility of the manufacturer or installer. It should include:

  • the use of fail-safe equipment
  • electrical diagrams showing all the components, their connections, and their location
  • compliance with the standards, regulations, and guidelines that apply to your installation
  • clean wiring with references to the electrical diagrams
  • documentation of changes and updates to the electrical diagrams as needed.


2. Suitable charging equipment

This equipment, which includes alternators, generators, regulators, and chargers, must be:

  • fail-safe
  • suitable for lithium-ion battery charging
  • adjustable to meet your needs in different situations, such as lowering charge voltage when your installation is not being used.


3. Early warning

Any instance of your installation drifting outside normal operating conditions could indicate the onset of a problem, such as:

  • charge voltage above the value set on the charger (caused by changed charger settings or a defective charger)
  • current above the theoretical maximum consumption value (defective equipment, short-circuit)
  • higher temperature of one cell (poor cell connection, failing cell).

The sooner you learn about any situation such as these, the greater the chance that you can find the cause and correct it before it gets worse.


4. Corrective measures

These are the actions undertaken to address the cause of an early warning. They can involve human intervention or automated commands:

  • stop all chargers
  • disconnect all non-essential equipment (keeping safety equipment operational)
  • start/stop a generator
  • start/stop a cooling or warming system for the battery enclosure
  • start/stop any piece of equipment that requires high charge (boiler, water-maker).

These measures are intended to avoid reaching level 5.


5. Critical alarms

If corrective actions do not have the intended effect and the situation gets worse, critical alarms must be triggered before the threshold for level 6 protection is reached. These alarms gives you a short space of time to react:

  • correct the problem
  • connect safety and essential equipment to an alternative energy source
  • prepare for a power outage
  • shut down the system.


6. Protection of last resort

This is generally the disconnection of the battery bank by a circuit-breaker, a short time after the critical alarm.

It is also the protection level that gets activated instantaneously (fuse) in the case of critical danger like a short-circuit (no time for early warning).

Note that many EMS provide only this level of protection, so do your research.

If safety is a concern, ensure that your installation/EMS will:

  • execute levels 3 and 4 protective measures (early warning, correcting or mitigating problems before battery disconnection)
  • differentiate between levels 5 and 6 (alarm activation before the battery is disconnected)


TAO EMS executes levels 3 to 6 protective measures in a flexible manner.

User-defined warnings and alarms based on voltage, temperature, current, and SOC

Six outputs and CAN connectivity to control safety devices and other equipment


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