Written by Cláudio Lopes, LISSOL
Physical characteristics
For the same capacity, a pack of lithium can weight 50 to 70 % less. Lithium cells can be installed and used without restrictions of orientations. Lithium cells are stacked very closely creating a very consistent set reenforced with fixation, rigid cover, and protective part. This set, results in a strong and consistent structure against vibrations that occur over time.
Internal inclusion of the electronic protection system (BMS)
The pack of the lithium battery always includes an internal electronic device (BMS), from Battery Management System, to monetarize and control all the battery.
This has the function of controlling tensions and currents, totally (all the pack) or per cell, namely for a longer battery duration, control of maximal and minimal tension, maximal currents of charge/discharge, protection against inverted polarity, shorth circuit. Automatic control of balancing the internal cell as so it’s life cycle.
Charge Algorithm
Lithium batteries can be charged with chargers that use algorithms of charge, Constant Current (CC), Constant Tension (CV). Any type of charger can be used if it respects the maximum levels of tension and current.
For more durability the charger must be programed according with the tensions “Bulk”, “absorb”, “float” according to supplier specifications. The characteristics of a lithium battery allow it to be charged totally in less than an hour, when necessary. This is an advantage for critical systems.
Efficiency
The relation between charge energy with discharge energy is very high, usually superior to 99%. Resulting from the few losses in the processes of charge and discharge, primarily when the currents of charge and discharge are limited to the recommended. An excellent low level of auto-discharge, usually below 3% per month allows Its usage in systems of long duration, virtually without auto-discharge.
The curve of tensions of discharge and functioning of the cell are very near of the rated voltage, low fall of tension.
Very useful for efficiency and sizing of systems that need a lot of energy and tension control of great stability.
Available Energy
Unlike the traditional technology of acid batteries, lithium batteries allow a total discharge of it's capacity, allowing a bigger capacity of available and usable energy, maintaining oje direct relation between capacity and available energy.
Low effect, “Peukert’s Law”, the battery can discharge to various levels of intensity providing the same quantity of energy. Meanwhile in the acid traditional technology, the value of energy of discharge can be much more inferior in case the discharge is made with a current superior to the recommended, leading to the loss of energy available and specific damage.
Advantages of the Lithium cell
Wide gamma of temperatures of operation.
Consistence and predictability of operation allow a better sizing of more complex and advanced systems.
The usage of the BMS technology eases the interconnections between different batteries, their supervision, and their integration in centralized monitoring systems.
The construction of a battery it’s based on the use of smaller cells, this function it’s used to facilitate the design and final appearance, easing its installation in more restrict places.
Less maintenance. No need for acid control.
Longer lifespan, allowing the return of its investment when used in systems with a longer time of usage.
For the same quantity of energy, it has less size.
Diverse ways of processes of charge and discharge
High efficiency, low auto-discharge, high relation between the battery and the energy available.
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