DIAMOND® CHARGE TECHNOLOGY
Innovative Charger Technology
All battery chargers used in industrial applications are electrical converters of the same type (AC/DC), designed to transform the AC input voltage available from the mains to a DC output voltage.
In order to charge batteries properly and safely, it is not sufficient to apply a DC voltage to them, but it is necessary to control the charging current and voltage to follow well defined trends, that are commonly defined as “Charging Curves”, and to implement a number of protection functions to prevent potential malfunctions.
A large number of electrical technologies and circuit topologies can be used to design battery chargers, from very simple to highly sophisticated solutions. Moreover, batteries and chargers can be matched in different ways, depending on the requirements and constraints of each specific application.
The mix of all these variables, summed with the potential of customization and differentiation given by microprocessors (used today in all modern battery chargers), determined a proliferation of models, types and versions in the market.This document is intended to give you a simple but complete view of the chargers available today, and to help you to identify the best product for your unique application needs.
CLASSIFICATION BY TECHNOLOGY
Battery chargers can be classified by the type and construction of their core AC/DC conversion unit.
A first macro-classification is done by the frequency at which the power converter operates. Traditional types operate at line frequency (60 Hz, or “low-frequency”), more recent types operate at high frequency (in the range from 1000 Hz to 50,000 Hz, or “high-frequency”), and very new systems have been designed to operate at a frequency that is the result of the multiplication of the line frequency by a variable factor (360-720-1440-2880 Hz, or “multi-frequency”).
Within these three macro-groups, the classification is based on the components that are used and the circuit topology. After grouping together the most similar technologies, we have the following tree:
Line-Frequency Example: GECI Black Diamond ◦ Controlled Flux ◦ Ferroresonant ◦ SCR/Thyristors ◦ Saturable reactors
High-Frequency Example: GECI Gold Diamond ◦ High Frequency – Standard ◦ High Frequency – With power factor correction ◦ Hybrid High Frequency
Multi-Frequency Example: GECI GREEN Diamond ◦ Green Converter
In the past, only Line-Frequency chargers were available, but in the last two decades new semiconductors (MOSFETS, IGBTs) and control systems have been introduced. This allowed manufacturers to design new products and take advantage of these new technologies. The main advantages of increasing the operating frequency of a converter are the possibility to reduce size and weight (fundamental for portable chargers) by increasing the electrical efficiency, and to achieve very well filtered output currents (low ripple) without the need for large filters. Other significant improvements have been reached with the introduction of multifrequency power stages, that aim to take the best of the two worlds (low and high frequency) while minimizing cost and complexity. However, the most important features of battery chargers are not strictly dependent on the technology that is used, and the reality is that still today, in the market, there are excellent old products that are competitive with the most recent designs.
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Evaluation of a charger for industrial applications should be based on three main characteristics, that are independent by the technology. The most important features of a battery charger are not strictly dependent on the technology that is used for the power stage.
The operating frequency, the types of components or the age of the design are not sufficient to define the qualities of a charger, because there are no direct and unique correlations with quality of the control, ability to charge faster, reliability, efficiency, ability to support opportunity/rapid charging applications, etc.
Each application is different and, in any case, the qualities must be supported by experimental data in real-life conditions.
Quality and sophistication of the charge controller.
This will maximize battery life and ensure good and stable performances. Beside the basic controls on the charging curve, a good charger should include a set of protections against mistakes of the operator, an adaptive algorithm to recognize the real conditions of the battery (State of Charge, Age, Temperature) and to adjust the charge cycle accordingly, and should be equipped with a good display that shows all the relevant operating parameters.
Other important features, that are always useful but may be absolutely necessary to support the heavier applications, are a programmable real-time clock with calendar, a built-in datalogger to save charge history, an automatic battery-recognition system (with or without battery identification modules), a remote control system (ideally a WEB based type, with bidirectional capabilities), and advanced protection features like anti-arcing, reverse-polarity control and ground-fault detection.
Robustness and quality of construction.
This will protect investment and ensure continuity of operation. A good charger is not just robust and has a long MTBF (Mean-Time-Between-Failures), but it is designed around a clear and well organized layout, where components are easy to identify and replace, with no need for special tools and sophisticated calibration procedures. In this way, troubleshooting and repair can be done by any electrician, at low cost and with little impact on productivity.
Typical marketing materials contain words like “heavy duty”, “strong” and “reliable”, but in the field the best way to evaluate this aspect is to ask an electrician to watch a product inside and evaluate the construction robustness, the simplicity of the layout, and the quality of components and interconnections. The questions to be asked are: “Is it well built?” and “Can you repair it?”.
This characteristic is important to minimize energy cost and carbon footprint.
It is fundamental to understand that the energy efficiency of a charger depends on a combination of many factors.
Typically, the peak conversion efficiency (%) at full load is the first (and, sometimes, unique) parameter that is taken into account when the goal is to minimize energy consumption. This approach could be misleading, because chargers don’t operate always at full load, so the average efficiency (%) over the complete charging cycle is a better indicator. Unfortunately, this value is generally not disclosed by manufacturers, so real-life test results are necessary to know the truth.
To better understand this concept, we can use the example of car mileage: a car that has a great mileage at 50 Mph but poor mileage at other speeds will probably consume more gasoline than another car that reaches a fairly good mileage at any speed, even if the mileage at 50 Mph is not particularly good.
Similarly, with battery chargers, a system that gives a constant 82% efficiency over the entire charge may consume less energy than another system that reaches a 92% peak efficiency at full load but then operates at 70% in other moments.
This characteristic is important to save energy by minimizing the amount of energy that needs to be given to the battery in order to bring it to the desired State of Charge.
Batteries required more than 100% of the removed capacity to be returned, in order to reach the full state of charge and to achieve a proper mixing of the electrolyte.
Chargers that use a conventional finishing charge (at low current, eventually constant), need to apply a charging factor of 108-120%. Chargers that are equipped with advanced finishing charge systems (like the PulseMix, implemented in the IBCI Green Diamond chargers), allows to reduce the charging factor to 102-107%. This is possible because the high current pulses at the end of the charge generate a very efficient gassing of the battery, while the temperature rise and the time required to complete the charge are minimized. This feature helps to maximize the energy savings and to minimize the water consumption too.
BASSI and GECI joined forces in 2007, to create the new “DIAMOND” battery of chargers for the North American market. Bassi S.r.l.
Founded in 1974, Bassi S.r.l. is one of the World leading companies in design and production of EV battery chargers for industrial and commercial applications.
The company head office, laboratories and main manufacturing departments are located in the northern Italy, in a world-class, 100% solar powered facility. Other manufacturing and sub-assembly branches are located in the Eastern Europe, Asia and North America.
As a result of almost 40 years of continued R&D, one of the unique characteristics of the Bassi Company is the completeness of the product portfolio, which covers all the existing types of chargers and technologies: controlled and uncontrolled chargers, conventional and opportunity/rapid chargers, ferroresonant, controlled-flux, SCR, High Frequency switch mode, High Frequency Hybrid and Multifrequency.
The product range is completed by load banks and battery testers, battery monitors, fleet management systems, power supplies, transformers and converters.
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LOCATION: LUGO (RA) ITALY FOUNDED in 1974