All types of batteries are built from a series of cells of 1.2 Volts to 4 Volts each, depending on the type of cell used.
The reason that your portable radio or flashlight is supplied with more than one AAA, AA or D-cell battery is to increase the voltage and therefore the available power. The same technique is used on a standard 12 Volts car battery. These batteries are constructed with six individual 2 Volts cells.
Every single cell includes a unique chemical process. Despite of minimum margins during manufacturing and even with the highest quality of materials used, there will always be a difference between cells. The difference between cells will even increase due to aging and the charge and discharge cycles.
In 12V or 24V systems, built with standard lead acid batteries, the initial purchase price and the limited amount of cells used is not justifying the investment of a cell balancing system. The limited lifespan of 400 cycles will not dramatically increase with a cell balancing system. Therefore, in these applications a non balanced setup is accepted. Besides that, the charging process of lead acid batteries is a slower process and needs several hours of absorption and float to compensate a part of the cell unbalance.
The new battery system layout with higher voltages far above 100 Volts, even up to 1.000 Volts requires a large amount of cells connected in series.
Even if cells are used with higher voltages, like 3.4 Volts for Lithium-Ion and 3.7 Volts for Lithium-Polymer cells, it is still necessary to connect 28 up to 250 cells to reach the requested system voltages. A large team of single players like this needs a coach with a complete overview. This requires an advanced balancing system.
Two types of balancing methods are used: passive and active.
The passive balancing method is most widely used because it is less complex and easy to make and therefore cheaper. Passive balancing is used at the end of the charge cycle and works with switching resistors across the single cell(s) that is(are) fully charged until the last and weakest cell is finally balanced to fully charged levels. These resistors create unwanted heat and generate loss in valuable energy. Besides that, this method requires a well-controlled charge process to keep excessive heat buildup under control.
Active Cell Balancing
The active balancing method is an active system that constantly monitors and controls all voltages and states of charge or discharge per individual cell. Some applications use an external power supply for balance charging a selected cell in a system.
ESTechnologies went one big step further and uses an in-house developed, state of the art, internal active balancing and monitoring system board per battery module. The EST system is capable to balance fully automatically standalone within each EST battery module. All single cells receive, by activation of the module, automatically an unique data-address via an NMEA 2000 based EST-CanBus system.
Per cell, the system monitors voltage, SOC, SOH, temperature and all safety parameters. In case of an unbalance between cells, the system uses the cell with the highest voltage to transfer a part of that energy to the cell with the lowest voltage. With an accuracy of 0,005 Volts between cells and a response time in milliseconds. This transfer of energy is almost lossless and therefore will hardly generate any heat at all.
The ESTechnologies modules are constructed with only 14 large 3.7 Volts Lithium Polymer Cells of the highest quality available today. All 14 cells are connected in series to be able to make the requested voltage. This is also the only way to make single cell balancing possible. Connecting smaller cells in parallel and series to create larger capacities, makes this active balancing useless and even technical impossible. Result: The ESTechnologies Marine Lithium Polymer Battery Modules are always completely balanced.
Active Series Modules Balancing
Active Balancing is used per serial system at any moment, during charge or discharge or standby modes: In a typical EST Power system set-up there are 7, 13 or up to 18 battery modules connected in series. We just learned that every EST battery Module is built with 14 single cells. All single cells are monitored by an NMEA 2000/CanBus based controller. This advanced process results in a safe and useful 52 Volts battery module. For systems with higher voltages which consists of a series connection of several modules, balancing between all connected battery modules in the same series is required. All single cells that are part of one chain of modules connected in series are automatically monitored and constantly balanced actively via the interconnecting NMEA 2000/CanBus system cabling. In case of an unbalance between cells or modules, the Active Balancing system uses the cell with the highest voltage to transfer a part of that energy to the cell with the lowest voltage within any of the modules of the whole chain in that system. With an accuracy of 0,005 Volts, the balancing system reacts in just milliseconds. Therefore a complete EST Advanced Marine Battery System is always 100% balanced in all states of charging levels, at all times. In practice, the use of battery systems on board of ships tells us that batteries are constantly switching between charge or discharge modes between 30% and 85% of charge. In this case the commonly and most used passive balancing setup, which can only be active at the top end of the charge period, will never balance the individual cells, resulting in a shorter battery lifespan overall.
ESTechnologies uses just two cell models in both their modules, a 3.7 Volts/100 Ah and a 3.7 Volts/200Ah. Both cells are designed, built and tested for Military applications. Compared to civil applications, this results in very high safety standards and long life span. ESTechnologies combined this high end cell technology with the experience of the EST founders. They gained their experience by working in the marine/boat builder industry for more than 25 years.
ESTechnologies presents the world first Marine Lithium Polymer Battery with a full Lloyd`s certificate for Lloyd`s certified vessel based systems up to 1.000 Volts, including the system power connection cabling.
Next step is to upgrade this precious Lloyd`s certificate with the approval of the use of a non ventilated location to place these battery systems making installation easier and much cheaper for the boat builder. Dear client, please neglect the drama films on YouTube, these amateurs just need to show themselves. To get a single cell to explode or burn they need to put more than 10 times the nominal voltages on the cells shown. Even if we want, how can we get 10.000 Volts or more on board of a ship to get this same reaction? ESTechnologies Marine Lithium Polymer Batteries are delivered as a fully controlled and protected system.
Because all cells are made to military specs, every EST battery module is equipped with one internal main fuse per cell, this means 14 main fuses per module (!). Also the advanced active balancing circuit board is taking care of safety issues. In case of eventual system failure, each of the modules will automatically disconnect the whole system serial setup by opening the plus and minus 2.500 Amps main contactors, which are mounted in the supplied EST system battery pack controller. This EST system battery pack controller is part of deliveries in larger systems and is used for system main fusing, for battery monitoring and energy control and connection to the ships energy system and controls.
ESTechnologies uses cells that won’t burn neither explode, even when tried (as can be seen on YouTube). These certified modules are safely constructed with our high impact resistant and IP65 polyethylene (LDPE) casing.