WO2017111751A1

WO2017111751A1 - Internal resistance measurement method for power supplies like batteries or supercapacitors

Info

Publication number: WO2017111751A1
Application number: PCT/TR2016/050516
Authority: WO
Inventors: Parviz HASANOGLU ALI ZADA; Ramazan NEJAT TUNCAY; Salih Baris Ozturk; Omer Cihan KIVANC
Original assignee: Okan Universitesi
Priority date: 2015-12-21
Filing date: 2016-12-19
Publication date: 2017-06-29
Also published as: TR201516481A2

Abstract

The invention relates to a new internal resistance measurement method for power supplies like accumulators, batteries or highly secured capacitors which performs direct measurement by means of a multimeter and a switch.

Description

INTERNAL RESISTANCE MEASUREMENT METHOD FOR

POWER SUPPLIES LIKE BATTERIES OR SUPERCAPACITORS

DESCRIPTION

Technical Field of the Invention

The invention is about a new internal resistance determining method which makes assembling easy, developed for highly secured capacitors and performs direct measurement.

State of Art

A condenser is a basic electricity and electronic circuit element formed by placing a non-conducting material between two metal plates through utilizing from the electrons' capability to store electrical charge in the electrical area by polarizing. Also named as capacitor, these condensers started to be developed in 18^th century and had an important role in the development of today' s technologies and also they are indispensable elements of electricity-electronic branches. They are being used for storing electrical charge, reactive power control, preventing information loss and transition between AC/DC. Features of condensers vary from types of insulators used between plates, to operating and breakdown voltages and the amount of charge they can store. Physical sizes of condensers can vary depending on the operating voltages and charge amounts they can store.

Small sized micro systems became more spread as technology developed. These developments lead to a need for condensers that are small sized but have higher charge amount. In the direction of this need, super condensers with high capacities are being developed .

Super condensers are basically consisted of a dispersive surface and a large number of surface electrodes on a double layered electro-chemical structure in which electric power is stored . Dispersive surface blocks the physical contact between electrodes but also allows the passing of ions.

Surface electrodes in the structure of super condenser are nanosized, and then increase the surface area and capacity value to very high values. Super condensers can charge-discharge at very high speeds due to their incredibly low internal resistances and there is no chemical reaction in their internal structures. Also they have other advantages like durability, longevity, high number of cycles, and being less sensitive against the weather conditions. Super condensers are preferred both in small applications and as a power storage element in recent rapidly developed electrical vehicle applications for their high productivity and the materials they are being produced of are green friendly. Some of their prominent disadvantages are low energy density, being unable to make long-term storage due to poor discharge ratios, and their high costs.

Super condensers can not only energize 10 or 100 times fold per unit volume but also they can charge or discharge in high amounts comparing to rechargeable batteries. Super condensers are generally used in the applications which needs long term energy storage rather than fast charge or discharge features.

Super condensers are divided into three groups according to storage basis;

Double layered condensers (EDLCs) - very high electrostatic activated carbon electrodes or its derivatives and double layered electrochemical inclusive capacitances

Pseudocapacitors - pseudocapacitors involving transition metal oxides or conductive high electrochemical polymer electrodes , Hybrid condensers - asymmetric electrodes such as lithium- ion, capacitances that are mostly inclusive of electrostatic and electrochemical .

The most determinative criteria in terms of characteristic features of batteries and condensers are lined up as voltage, capacity of the battery, internal resistance and charging time.

The voltage produced by a battery or an accumulator is characteristic feature of that battery or accumulator, this voltage value is also called nominal voltage value of battery. The energy produced by a battery or an accumulator is indicated as ampere-hour (Ah) . One thousands of one ampere-hour is 1 milliamp-hour (ImAh) .

There is an internal resistance which absorbs some of the energy produced by electrical energy sources. This internal resistance serially consists a voltage divider with the energy produced by battery or accumulator. For this reason, as the current produced by batteries, condensers or accumulator increases, then the voltage transmitting over the charge decreases. As internal increases, then battery, condenser or accumulator give less current without changing the voltage transmitted over the charge .

During the current draw from generator, the resistance measured at its ends is lesser than EMK (Electromotor power) , because there occurs a voltage drop in internal resistance of generator while current is transmitting through generator. As the current draw increases, the voltage drop in the resistance also increases; on the other hand, the resistance measured at the ends of generator decreases.

Charge and/or discharge of super condenser depends on the movements of dispersive electrodes and carriers (ions) inside the reticular structure of dispersive electrodes. Lost internal DC resistance ingenerates during this measured movement. Internal resistance increases with RC (resistance/condenser) element pores of series electrodes, gradual electrical model and increased penetration pore depths of charge carriers. The internal resistance (Ri) , charge/discharge time of a super condenser depends on factors of capacitances (C) . So, internal resistance affects the charge/discharge times of super condensers. Charge/discharge time is found by this formula:

Time constant (T) in this formula, determines the charge/discharge time. Charge/discharge time is calculated based on the certain structure details. For this reason, it cannot always be calculated with abovementioned formula. Present charges of super condensers including charge, discharge and peak current do not work without generating chemical connection; because discharge and peak currents are not limited with reaction limitations. Present charge and stability cycle of rechargeable batteries can be higher. Present charges are limited by a significantly lower internal resistance for batteries .

Since the internal resistances of batteries are very small, Ri is not considered in the discharges with low currents. But in some occasions where current draw is so high, voltage drop in the Ri of battery can increase and this situation makes an appearance as a decrease in the useful voltage of poles. Here Ri shows the heat eventuated in the internal resistance of battery and this heat can cause the temperature of battery to increase during the discharge of that battery with high current. Also this heat is a loss for external circuit and since this loss is proportionated to square of current draw it decreases the Watt efficiency of battery during the discharge with high current.

For any kind of cell type, internal resistance is determined by several methods, some of them are:

VDA progressive current management,

Current closure method,

Measurement with alternative current method, Measurement with impedance spectroscopy method, Power loss method

VDA progressive method is a test performed by analyzing the resistance reactions of a battery cell, given under the

discharge current impacts at different sizes in different time periods. Throughout the test, discharge current impacts at different values are kept constant and resistance values of battery cell are analyzed.

For current closure method, the internal resistance of battery is determined from the voltage change which is generated during the breaking of the current transmitted over the battery cell. The biggest disadvantage of this method, which is not hard to apply, is that accuracy of the results are not certain.

The method of measurement with alternative current is a commonly used method. It is performed by alternative current damping method at fixed frequency. It is frequently preferred since it does not harm the battery cell, it is easy to apply and it gives results in a short time. But this method is suitable only for measuring and comparing the internal resistances of same type cells . Frequency dependency of a battery cell impedance is analyzed by impedance spectroscopy in this measurement with impedance spectroscopy method. So, detailed information about the behavior type of a battery cell can be obtained by this method. The biggest advantage of this method is that it does not cause any harm in the cell. But the expensive equipment required for applying this method makes this method disadvantageous.

Energy efficiency and the amount of loss energy and internal resistance is calculated by figuring the charge and discharge powers of a battery cell in the power loss method. This method requires auxiliary materials for abovementioned energy calculations .

There are some several disadvantages of these methods in terms of technical and economic aspects. Some of these disadvantages are; application difficulty for technicians, analyzes that requires long terms, low dependability, long quality control time during the production, difficulties in the assembling, and non-conformance with the different performances of batteries.

"CN104330636" numbered patent application is examined within the state of art. An internal resistance measurement method of a lithium ion battery is described by the subject invention. This invention is about finding the internal resistance value of a lithium ion battery as a result of some periodical tests performed under fixed temperature and fixed moisture.

In this "KR20150028410" numbered patent application, a new internal resistance measurement method is being described within the state of art. By this subject method, internal resistance is calculated by applying a current to battery whose internal resistance is to be measured by taking charge/discharge currents and equivalent impedance model of battery into consideration. Purpose of invention:

The purpose of the invention is to reveal a new measurement method which provides the measurement of internal resistances of batteries and super condensers.

Another purpose of the invention is to make it possible to directly calculate the internal resistances of energy sources such as batteries and super condensers.

Another purpose of the invention is to reveal an internal resistance measurement method which has a modular structure and can be applied to energy sources of different types.

Another purpose of the invention is to reveal an internal resistance measuring method that can be easily applied by many users .

Another object of the invention is to reveal a new internal resistance measuring method which has a high accuracy and is easy to apply.

Explanation of figures:

Figure 1. Single Element Test Circuit Connection Figure 2. Half Circuit

Figure 3. Multi-element Test Circuit Connection

The parts shown in the figures are numbered one by one, and the corresponding part names are as follows:

1. Half circuit

2. Multimeter

3. Switch Explanation of Invention

The subject method of invention is a method of measuring internal resistance of accumulators, batteries and condensers, which is developed to end the complexity of the internal resistance calculation methods used in the common situation of method. The internal resistances of single-cell batteries connected in equivalent series or super condensers can be calculated by so- called method.

The working principle of the subject internal resistance measuring method is about to form a closed circuit by connecting the single-cell battery or the super condenser to another equivalent single-cell battery or super condenser in series or cross-connection and to use the total resistance value on this circuit . A half circuit (1) apparatus is used to carry out the internal resistance measuring method subject to invention. There is a power supply on the so called half-circuit (1) which is equivalent to the power supply whose internal resistance is to be measured. There is a switch (3) and (1) a multimeter (2) on the half circuit (1), other than the power supply which changes depending on the power supply whose internal resistance is to be measured .

This subject internal resistance measuring method can be easily used in single element systems. It is also a method that allows the calculation of the internal resistances of each single-cell battery or super condenser which are connected in a series in multi-element systems. This method is realized with the help of a simple Multimeter (Amper-Volt-Ohm) (2) .

The first step to measure the internal resistance of a single cell battery or super condenser in a single element system with this subject internal resistance measuring method is to connect the power supply whose internal resistance is to be measured with a different equivalent power supply in series and cross- connection by placing an "on" positioned switch (3) between them. After equivalent power supplies are connected in series with an "on" positioned switch (3), an Multimeter (2) is added to the circuit in a way that their ends are connected to both ends of the switch (3) . Thus, as seen in Figure 1, the circuit required to measure the internal resistance of a single power supply is made ready.

The first step to make the internal resistance measurement with the prepared single-element circuit is to bring the switch (3) to the "off" position. Equivalent power supplies connected in series to each other balance each other in this way and have identical voltage magnitudes of + E / -E . As there are two equivalent power supplies with identical voltages on the circuit, the internal resistances of the respective power supplies become equal to each other. Then the total resistance value on the circuit is read on the Multimeter (2) by turning the switch (3) in the "off" position to the "on" position. The total resistance on the circuit is the sum of the internal resistances of the power supplies. That is, the resistance value read on the Multimeter (2) after the switch (3) is turned "on" becomes the sum of the internal resistances of the two power supplies. When the read resistance value is divided into two, it gives the internal resistances of both power supplies. Thus, with a simple operation, it gives the internal resistance of a battery or super condenser.

The subject internal resistance measurement method can also determine the internal resistances of the power supplies serially connected in a multi-element circuit. For this, the subject half-circuit (1) structure has to be suitably connected to the single-cell battery or super condenser element which are positioned in series connection in a multi-element circuit in which the internal resistance value is to be measured.

The circuit required to be established in order to measure the internal resistance of a power supply connected in series in a multi-element circuit by subject method is established with the new connections from both ends of the power supply whose internal resistance is to be measured. The outputs from both ends of the power supply, whose internal resistance is to be measured, are combined with the ends of the half-circuit (1) shown in Figure 2.

As shown in Figure 3, a new and small circuit is established for the internal power supply whose internal resistance is to be measured. On the half circuit (1) which establishes the so called circuit, there is a power supply equivalent to power supply whose internal resistance is to be measured. There is also a Multimeter (2) , which can make the measurement by means of a switch (3) , on the said half-circuit (1) . The ends of the Multimeter (2) are positioned so as to be connected to the two ends of the switch (3) as shown in Figure 3. When the this established small circuit is considered as one, the two equivalent power supplies on it must be cross connected to each other.

When the switch (3) on the established small circuit is brought to the "off" position, the equivalent power supplies on the small circuit have identical voltage magnitudes of + E / -E by balancing each other. Thus, the internal resistances of the two equivalent power supplies on the small circuit are equalized. Then the total resistance of the small circuit is measured through the Multimeter (2) connected to the small circuit by switching the switch (3) to "on" position. The value of the resistance read on the Multimeter (2) indicates the sum of the internal resistances of two equivalent power supplies connected to the small circuit. Since the internal resistances of equivalent power supplies are equal, when the resistance value read on the Multimeter (2) is divided into two, it gives the internal resistance of the battery or super condenser whose internal resistance is desired to be measured.

By the same method, the internal resistance of each power supply connected serially in a multi-element circuit can be measured. However, the power supply on the half-circuit (1) to be used during the measurement of each power supply whose internal resistance is to be measured, must be equivalent to the power supply whose internal resistance is being measured. It is not possible to make a reliable internal resistance measurement unless the cross-connected power supplies on the small circuit established with the half circuit (1) are equivalent.

Thanks to this subject internal resistance measuring method, it is possible to determine the internal resistance values of batteries and super condensers in single element or multi element circuits by an easy, simple method.

Claims

1 . The invention is a new internal resistance measurement method providing a simple measurement of internal resistances of power supplies like accumulator, battery and condenser and its features are consisted of following process steps:

- One piece of switch (3) at "on" position, one piece of multimeter (2) whose ends are connected in a way to correspond to ends of switch (3) and the preparation of the half-circuit (1), which will perform the measurement of internal resistance process, by connecting a power supply identical to power supply whose internal resistance is to be measured to any end of the multimeter (2),

- If power supply whose internal resistance to be measured is not connected to any circuit; connecting this power supply to half circuit (1) in a way to transform half circuit (1) into a closed circuit inversely to identical power supply on the half circuit (1) and constituting a closed circuit by half circuit

(1) ,

- If power supply whose internal resistance is to be measured is connected to a circuit; constituting a new closed circuit by connecting open ends of the half circuit (1) to two ends of power supply whose internal resistance is to be measured in such a manner that identical power supply on the half circuit is cross- connected with the power supply whose internal resistance is to be measured,

- Charging the identical power supplies on closed circuit with same size values at opposite poles by switching the "on" positioned switch (3) to "off" position in this constituted closed circuit, - Switching the "off" switch (3) on the closed circuit to "on" position again,

- Reading the closed circuit total resistance, which consists of sum of equal resistances of power supplies which have opposite pole identical charge values on the closed circuit, through multimeter by switching the switch to "on" position,

- Finding the internal resistance values valid for both power supplies in the closed circuit by dividing total closed circuit resistance, which is read through multimeter and is the sum of equal internal resistances of power supplies into two.