( OPERATING INSTRUCTIONS Version 05/14 ( Rechargeable Batteries and Charging Technology Understanding and Using Item No.
Table of Contents ( Page 1 2 Becoming familiar with the components of the learning package....... 4 1.1 The Experimenting Board............................................................... 5 1.2 USB Connection Cable................................................................... 6 1.3 Solar Module.................................................................................. 7 1.4 Diodes............................................................................................ 8 1.
Page 10 Charging a Nickel Zinc Cell.................................................................... 36 11 Charging Lithium Rechargeable Batteries........................................... 40 12 Monitoring Charging............................................................................... 45 12.1 Rechargeable Battery Tank Display.......................................................... 45 13 Testing Rechargeable Batteries............................................................ 48 13.
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1.1 The Experimenting Board The experimenting board, also called a lab plug board or simply plug board, permits setting up the experiments without using a soldering gun. It comprises of contact springs inside that are connected to each other in a row system. The electronic components and connection wires can be plugged into the contacts repeatedly and thus permit circuit setup without soldering or screwing. Connection wires diagonally cut off with a wire cutter can be pushed in most easily.
1.2 USB Connection Cable The USB connection cable of the learning package has a USB A plug on one side and a pin plug for the plug board on the other side. This permits connecting the 5 V (Volt) power supply of a USB source (USB mains plug) to the plug board. Important! When connecting the pin plug to the plug board, always observe polarity! The red cable to the pin plug is the plus pole, the black is the minus pole. Fig.
The reason: Basically, high power devices at the computer USB socket may have a current consumption of 500 mA, low power devices one of up to 100 mA. Unfortunately, not all USB sockets (depending on computer type) are short-circuit protected! Often, there is only one fuse soldered in at the socket, sometimes also the corresponding resistor. Some devices have a fuse that will reset on its own, in others it must be replaced after a short circuit.
a) b) Fig. 003: a) Solar module with protective film, b) Circuit symbol 1.4 Diodes A diode only permits current to flow in one direction. They are therefore used to rectify alternating voltages and block undesired polarity in direct voltage. The function of a diode can be imagined as a kind of check valve (as in water installations) in regular operation.
a) b) Fig. 004: a) Silicon diode type 1N 4001; the cathode of the diode can be recognised by the printed-on dash. The other connection wire is the anode. The technical current direction goes from the anode to the cathode. b) Circuit symbol of the diode In passage direction (circuit symbol arrow), considerable current starts flowing in the silicon diode, such as the 1N 4001, only from a voltage of approx. 0.6–0.7 V or 700 mV (millivolt) onwards. a) Fig.
1.5 Light Emitter Diodes The LED (light emitting diode) has another property in addition to those of a regular diode: It lights up when voltage is applied. LEDs should usually always be operated with a dropping resistor for current limitation. Red LEDs require the lowest voltage (1.8 V). Then there are yellow, green, blue and last white LEDs with the highest voltage (up to 3.6 V). a) c) b) Fig.
1.6 Transistors Transistors are active components that are used in electronic applications to switch and amplify current and voltage. The bipolar transistors contained in the learning package have the type designations 2N 3904 and 2N 3906. These are complementary small-power transistors that are suitable for a maximum operating voltage of 30 V and a current of up to 200 mA. Complementary means that they are a matching transistor pair of an NPN and a PNP transistor.
How the transistor works A small current applied to the basis-emitter section can control a large current on the collector-emitter section. I.e. if a low basis current is flowing (positive in NPN transistors, negative in PNP transistors), the transistor will conduct the current from the collector to the emitter or vice versa. If no current is flowing through the basis or if the basis connection is with negative (NPN) or positive potential (PNP), the transistor will block. Fig.
a) b) Fig. 009: a) Resistor, b) Circuit symbol The resistor values are encoded and printed on as coloured rings. The learning package contains carbon layer resistors with the following values and colour rings according to the table: Amount Resistance 1st ring 2nd ring 3rd ring 4th ring 1st number 2nd number Multiplier Tolerance 1 1.2 Ω Brown Red Gold Gold 1 1.
1.8 Electrolytic Capacitors Electrolytic capacitors (elcos) have a high capacity as compared to regular capacitors. Due to the electrolyte, an electrolytic capacitor is polarity-dependent and the connections are marked with a plus and a minus pole. If a component is connected »swapped« for an extended period of time, this will destroy the electrolyte of the capacitor. The printed-on maximum voltage indication should not be exceeded. Else, the insulation layer may be destroyed.
1.9 Battery Holder The battery holder is used to hold the rechargeable battery in the AA-mignon format. The battery holder can also be used for the AAA-micro format if the spring at the minus pole connection is elongated a little. a) b) Fig.
1.10 Experimenting Cable Use the red and black experimenting cables at the ends of which alligator terminals are connected to quickly and simply electrically connect parts to the circuit and to each other – without soldering gun and screwdriver. It is sensible to use the red connection cables for the plus pole and the black ones for the minus pole. Fig. 012: Experimenting cable with alligator clamps 1.11 Jumper Wire Wire bridges can be made of the enclosed jumper wire.
2. Use of the USB-Cable The enclosed USB cable should be connected to a 5-V-USB plug-in mains adapter as it is used for charging mobile phones. Generally, connection to the USB output of a PC is possible, but advised against. The reason: At accidental short circuit when setting up the circuit, the current limitation in the computer (usually in the form of a resistor) may be destroyed. 2.
c) Fig. 013: a) and b): Connect pin plugs to the plug board; connect the 1.5Ω protection resistance to the plus pole. c): Add the LED and the 1kΩ resistor. In the next step, plug in the red LED. Observe that the longer connection wire reaches the plus pole. Additionally push the 1 kΩ resistor into the plug board. If the USB plug is now connected to the USB power source, the LED should light up. Fig.
3. Storing Energy The principle of energy storage with electrical current that cannot be perceived with our senses can be compared and explained with a principle that we can observe in water: A water container is filled with water from a tap. The water can be taken out again at a later time. Fig. 015: Principle of energy storage, illustrated by a water tank The »energy storage« has different forms in the electronic world. The learning package contains an electrolytic capacitor.
3.1 Energy Storage with the Electrolytic Capacitor Test setup: Plug board, cable with USB-A plugs and pins, resistor 1 kΩ, red LED, electrolytic capacitor, 1,000 µF The preceding setup is expanded by the electrolytic capacitor. The connection wires of the electrolytic capacitor point to the plus pole rail of the plug board with their plus poles. If the electrolytic capacitor is plugged in correctly, plug the USB plug into the USB plug-in mains adapter. The LED lights up.
4. Familiarising Yourself with Battery Types The most common battery types used in everyday life: 1. Lead batteries (lead acid, lead gel), e.g. starter battery in the car. 2. Nickel cadmium (NiCd; no longer being sold), often used in cordless screwdrivers. 3. Nickel metal hydride (NiMH) 4. Nickel zinc (NiZn; new on the market) 5. Lithium (Li) in very different designs The lead battery is familiar from cars as „starter battery“. This battery type is costefficient, long-term stable but heavy.
Fig. 018: Experimenting setup with alligator clamps Fig.
Usually, LEDs should be operated with a dropping resistor. Since the solar module will only deliver a limited current and this is a short-term experiment, you can make an exception to find out which one is the permanently lit LED and which one the flashing LED. The flashing LED is then marked with a piece of adhesive tape for the further experiments. Fig.
6. Charging Rechargeable Batteries with the USB Source USB is a standard in the computer area and widely distributed. Electronic devices, computer accessories, such as external hard discs, but also small lamps, fans, etc. can be operated with it. Most mobile phone providers now offer micro USB as the standard device socket for the charging contact.
The USB source is great for charging experiments with smaller rechargeable battery cells. Use requires electronic circuits that consider the special charging conduct of the respective rechargeable battery types, though. Fig. 022: USB-cell-NiMH, mignon cell with integrated USB adapter Fig.
7. Charging NiMH and NiCd Rechargeable Batteries Test setup: Plug board, cable with USB-A plug, resistor 100 Ω, LED orange, battery holder, rechargeable battery AA or AAA, if present: Multimeter The rechargeable batteries, such as the NiMH rechargeable batteries and the NiCd rechargeable batteries, are alternatives to disposable batteries. The last rechargeable battery type listed is no longer sold. Nickel metal hydride rechargeable batteries are currently the most common rechargeable battery type.
Fig. 024: Setup plug board; a mignon rechargeable battery is being charged. Fig. 025: Circuit diagram Additional test (with a multimeter): Wire the multimeter in the milliampere range in series with the rechargeable battery. You can then read the current charging current, see figure 026.
Fig. 026: Measuring setup Fig. 027: Circuit diagram A multimeter can be used to check the charging current and, of course, measure the rechargeable battery voltage. To measure the rechargeable battery voltage, connect the cables of the multimeter right to the battery holder (in parallel to the rechargeable battery).
8. Constant Current Charging Test setup: USB cable, plug board, 1 resistor 1.5 Ω, 2 resistors 1 kΩ, 1 resistor 1.2 Ω, LED orange, Schottky diode BAT 42, battery holder, rechargeable battery mignon AA or micro AAA Constant current charging is a wide-spread way of charging rechargeable batteries in simple chargers. Depending on the battery capacity, the flat rechargeable battery is charged for a defined time with constant current. Fig.
There are also chargers with thermal monitoring and deactivation (e.g. in rechargeable batteries of low-cost cordless screwdrivers). This works best with NiCd rechargeable batteries, since they convert the energy flowing in from the charger into heat when fully charged. Thus, the electronics can understand that the rechargeable battery is now fully charged.
Memory Effect If not the entire capacity is used after discharging the rechargeable battery and the rechargeable battery is only partially discharged and then charged again, the rechargeable battery will „remember“ this condition and only provide this amount to the consumer the next time it is discharged. The charged battery then loses more and more useful capacity in the course of its service life, since the cadmium cathode forms crystals that reduce the rechargeable battery output.
The voltage distributor, comprising of R2 and D2, as well as the basic resistor R4, can be changed as well. This changes the constant charging current. You can thus first experiment with R4, i.e. replace the 1 kΩ-resistor (R4) with the 2.2 kΩ-resistor of the learning package, to get a lower charging current for the rechargeable battery. Fig.
9. Impulse Charging Test setup: USB cable, plug board, flashing LED, LED orange, diode 1N 4001, transistor T1 2N3904, transistor T2 N3906, resistor 10 Ω, 2 resistors 1 kΩ, battery holder, rechargeable battery AA mignon or AAA micro Impulse charging mostly prevents the memory effect even in older rechargeable battery cells. Short current surges will charge the rechargeable battery cell. The rechargeable battery is charged faster or more slowly depending on wiring.
The flashing LED and the resistor R2 together form a voltage distributor. The LED emits impulses to the basis of transistor T1. T1 Controls the basis input of transistor T2 via the collector-emitter section. It releases the current flow to the rechargeable battery as longitudinal transistor. The orange LED shows by its flashing brightness whether and how much current is flowing to the rechargeable battery. Fig.
If a multimeter is at hand, the pulsating and rising rechargeable battery voltage can be observed. If the diode D2 is bridged, charging is faster (more charging current), but at the expense of the orange LED‘s service life. Fig.
10. Charging a Nickel Zinc Cell Test setup: USB-cable, plug board, red LED, orange LED, resistor 100 Ω, battery holder, NiZn rechargeable battery AA mignon or AAA micro. The nickel zinc cell (NiZn) is a very old and also more recent development on the rechargeable battery market. The benefit of this cell type is a higher cell voltage of approx. 1.6 V. Thus, it is better to replace disposable batteries (1.5 V).
It is interesting that the capacity in the NiZn rechargeable battery is not indicated in milliampere, but in milliwatt hour. The voltage of a freshly charged NiZn-cell is at approx. 1.8 V and the discharge end voltage, depending on current load, at about 1.2 V. Since the cell type is still rather new, there is little experience with the cycle number yet. Rechargeable battery cycles means the number of times the rechargeable battery cell can be completely charged and discharged before it is rendered useless.
It is important for the circuit setup for a simple charger that the charging end voltage is stabilised/limited to max. 1.9 V. If the current used for charging is lower, this is unproblematic and charging merely takes longer. For many rechargeable battery types, a gentler charge (at a lower current) is rather of benefit and contributes to a higher number of charging cycles. Quick-chargers charge rechargeable batteries in the shortest time possible.
Fig. 037: Circuit diagram The self-discharge of the NiZn cells takes place independently of the ambience temperature, according to experience in the area of approx. 5 – 7%.
11. Charging Lithium Rechargeable Batteries Test setup: USB-cable, plug board, red LED, 2 diodes 1N 4001, resistor 1 kΩ, cable with alligator clamps red and black, lithium rechargeable battery. Most mobile phones and Smartphones, notebooks and tablet PCs work with lithium polymer (LiPo) or lithium ion (Li-Ion) rechargeable batteries. This rechargeable battery type has a high energy density at a low weight. The rechargeable batteries are replaceable or firmly installed (soldered in).
Note on discharge The final discharge voltage must never drop below 2.5 V. Otherwise, the rechargeable battery cell is destroyed. The rechargeable battery management usually integrated in the rechargeable battery therefore usually switches off at 3.0 V. It is recommended to „gently“ (dis-)charge lithium rechargeable batteries (only to approx. 30 %), since this will extend their service lives. If you want to build your own charger, precise control of the final charging voltage is mandatory.
The integrated safety electronics ensure that the rechargeable battery is not overcharged nor enters undervoltage when discharging, and switches off the connection to the rechargeable battery contacts. Thus, you can easily experiment with rechargeable batteries of mobile phones while the upper and lower temperature limits and the maximum charging current (1C) are not exceeded.
Fig. 039: Clamping connection with the rechargeable battery contacts Fig.
If a multimeter is at hand, you can measure the rising rechargeable battery voltage of the charging current. a) b) Fig. 041: a) Rechargeable battery charging and monitoring with the multimeter.
12. Monitoring Charging There are several ways to determine the output values around the rechargeable battery to be charged: • Display with LEDs • Measurement with a multimeter • LC display • Measurement and evaluation with the PC Light-emitting diodes can be used for simple measuring tasks (e.g. polarity display) or general function displays (e.g. whether a charging current is flowing or not). If detailed measuring information is desired, a multimeter is a good aid.
Fig. 042 shows the test setup for a very simple charge status display. After setting up the components, first connect the lithium rechargeable battery to the plug board with the alligator clamps. Then the orange LED lights up. Once the USB plug is plugged into the USB mains adapter, the rechargeable battery is charged at approx. 200 mA. A short time later, the flashing LED starts to flash and indicates that the rechargeable battery has reached the voltage of about 4 V.
Fig. 043: Circuit diagram of the charge status display The simple battery tank display is still implemented via the voltage measurement of the rechargeable battery. It would be progress to perform the voltages measurement under load (current tapping from the rechargeable battery). The load should have a current consumption of about 10% of the rechargeable battery capacity and could be activated at the time of measurement using a button.
13. Testing Rechargeable Batteries Everyone knows it: You have rechargeable batteries for many different uses in your drawer, but you do not know how much charge they still have. This is particularly important when using several rechargeable batteries. An electronic device will only work if all of them are sufficiently charged. Only measuring voltage will tell you little about the „charge capacity“ of a rechargeable battery. Fig.
13.1 Test at Low Current Test setup: Plug board, red LED, resistor 100 Ω, battery holder, NiZn rechargeable battery, micro AAA. The tests can be performed with different rechargeable battery types as well if you have a multimeter with which the rechargeable battery voltage under load can be displayed. The test at low current load usually is not a big problem even for older rechargeable batteries that have been freshly charged.
b) c) Fig.
Fig. 046: Circuit diagram Insert the rechargeable battery in the battery holder; when the rechargeable battery cell is fully charged. The LED lights up. Now push the button. The LED will darken slightly. With the 100 Ω resistor, about 15 mA of load current will flow. This is easily possible for the rechargeable battery. Therefore, the rechargeable battery voltage will only drop slightly. 13.2 Test at High Current Test setup: Plug board, red LED, resistor 1.
For the AA-mignon rechargeable battery, that means a maximum current of 1.5 A and for the smaller AAA cell a maximum discharge current of approx. 550 mA. Now the resistor R1 is replaced. Instead of the 100 Ω resistor, the 1.2 Ω resistor is now put into the plug board. If you push the wire button now, the LED will go out. The load current is approx. 1 A when calculated with the formula R = U / I and about 0.5 A when measured with the multimeter.
Fig. 047: Plug board setup Fig.
Fig. 049: Measuring setup with multimeter Rechargeable battery efficiencies The rechargeable battery efficiency states the amount charged in it and how much of it can be taken from the rechargeable battery again. The efficiencies of the different rechargeable battery types fluctuates strongly from approx. 70-90 %.
14. Rechargeable Battery and Solar Module Test setup: Solar module, plug board, plug pins, resistor 100 Ω, red LED The front of the unused solar module is protected with a film. This must be removed first. On the rear of the module there are two soldering connections with soldered-on cables. The module supplies direct current. Thus, there are a red cable, the plus pole, and a black cable, the minus pole, like in a battery.
b) Fig. 050: a) Connect the connection lines of the solar module to the plug board. b) The cables can be additionally secured with the plug pins. Place the solar module so that sufficiently bright light, preferably sunlight, falls onto it. If the sun does not shine during the experiments, you can replace it with a bright desk lamp, e.g. with a halogen light bulb (at least 30 W). Energy savings lamps and LED lamps are not suitable.
Fig. 051: Plug board setup; simple function test with the red light-emitting diode Fig.
You can perform this experiment with different light sources, e.g. with sunlight, a halogen lamp, a light bulb, a flashlight, an energy savings lamp, a fluorescent lamp, etc. You can tell by the brightness at which the LED is lit whether they are suitable or less suitable light sources. This experiment is important to teach you about suitable lighting for the subsequent experiments. 14.
Fig. 053: Plug board setup: Simple solar charger with LED as charging display Fig. 054: Circuit diagram; charging current display with one LED Both the red and the orange LED can be used in the charging circuit. The charging current is a little higher with the orange LED.
14.2 Solar Charger – What to Observe Test setup (as before): Solar modules, plug board, LED, battery holder, rechargeable battery Depending on rechargeable battery type, there is a number of options for customising the solar modules so that the rechargeable battery is charged in the best manner. The number of solar cells in series leads to the maximum upper charging voltage. The size and quality of the solar cells determines the maximum charging current.
Fig.
15. Using a Return-Current Block Experimenting setup: Solar module, plug board, electrolytic capacitor 1.000 µF, Schottky diode, resistor 100 Ω, LED red During solar charging of a rechargeable battery, the charge would „reverse“ unload through the solar module again if it didn‘t have the protective diode. Therefore, a return current lock in the form of a diode must be inserted. The diode works like a valve that only permits the energy current to flow in one direction while preventing it in the other.
Turn the diode around in the plug board once – what happens? The LED is no longer lit, since the current coming from the solar module is blocked. Blocking diodes prevent discharge of the energy storage via the unlit solar cell. a) b) Fig. 057: a) Plug board setup, b) Detail.
16. Using the Charge Controller Test setup: Solar module, plug board, red LED, electrolytic capacitor 1,000 µF, transistor T1 2N3906, resistor 2.2 k, button switch, battery holder, rechargeable battery In photovoltaic island systems, the entire current supply is gained by regeneration. The rechargeable battery storage stores this energy for later use.
Fig. 059: Circuit diagram charging controller With the charging controller built on the plug board, you can understand the principle of a serial shunt controller (longitudinal controller). The longitudinal transistor used for the charge control controls the current flowing from the solar module to the rechargeable battery and the voltage. In the test setup the control is achieved by manual cycling (manually) of the supplied current (cycle length and frequency) with the switch S1.
17. Solar Charge Monitoring of the Lithium Rechargeable Battery Test setup: Solar module, plug board, flashing LED, red LED, orange LED, Schottky diode BAT 42, electrolytic capacitor 1,000 µF, resistor 1 kΩ, alligator clamps, lithium rechargeable battery Fig. 060 shows the test setup of a simple charge monitoring system for solar charging of the lithium rechargeable battery. The upper red LED indicates the flowing charging current and is lit while the lithium rechargeable battery is charged.
Fig. 061: Circuit diagram of the charge status display Simplest rechargeable battery monitoring is implemented by voltage measurement of the rechargeable battery.
Fig.
18. Combination Chargers, Charging and Maintenance of Charge Test setup: Solar module, plug board, USB cable, flashing LED, red LED, orange LED, diode 1N 4001, resistor 1.5 Ω, resistor 1.2 Ω, 2 resistors 1 k, transistor 2N3904, battery holder, NiZn-rechargeable battery The self-discharge differs according to rechargeable battery type. If the rechargeable battery has been fully charged, then put in interim storage and is urgently needed, it is annoying to have to charge it again first.
b) c) Fig.
Function: If the USB plug is connected to the USB source, the orange LED lights up. The rechargeable battery is charged with a consonant current of approx. 70–80 mA. As of a rechargeable battery voltage of approx. 1.7 V, the flashing LED starts to flash, signalling that the rechargeable battery cell will soon be charged.
19. Solar Night Light Test setup: Solar module, plug board, orange LED, transistor T1 2N3904, diode D1 1N4001, resistor R1 100 kΩ, electrolytic capacitor 1,000 µF, alligator cables and clamps, lithium or old mobile phone rechargeable battery The following experiment charges an energy accumulator during the day. In darkness, it will emit the energy again – in the experiment setup via the lightemitting diode. The energy is emitted until the stored energy is used up.
Fig. 067: Circuit diagram for the solar night light Once it grows dark (e.g. with the solar module covered), the LED will light up. It goes out once the solar module is exposed to light again. The current from the lit solar modules blocks the T1 collector-emitter section via its basis. The rechargeable battery is charged via the diode D1. If no light hits the solar module anymore, the basis current stops and the collector-emitter section routes the current from the rechargeable battery via the LED.
Fig. 068: Cable light lantern according to the above principle For a long-term experiment, a red and a black cable can be soldered to the gold contacts of the older mobile phone rechargeable battery or the contacts can be connected via the alligator clamps.
Fig. 069: Covering one module will be enough to activate the night light.
20. Maintenance of the Capacity of Rechargeable Batteries 20.1 Rechargeable Battery Emergency Rescue Test setup: Lithium rechargeable battery, alligator cable, rechargeable battery cell (deep discharged) Rechargeable batteries that have been stored unused for a long time or connected to a permanent current consumer (e.g. an electrical watch) often collapse.
Lead batteries that have been used for an extended time form an insulation layer on the plate surface and thus become high-impedance and cannot be charged anymore. This can be remedied by alternating voltages being supplied to the rechargeable battery. Voltage applied with the „wrong“ polarity can help remove the inner insulation layers again. There are rechargeable battery refreshers to prevent this. The rechargeable battery is continually „shot at“ by short impulses in the millisecond range.
At the same time, there are some general properties and characteristics to be observed: • Chemical reactions are influenced by the ambience temperature. Too high and too low temperatures are harmful. The rechargeable battery is best kept at an even temperature in the range of approx. 10–15 °C. The refrigerator is too cold. • The higher the cell voltage, the faster will rechargeable batteries age during storage. Therefore, rechargeable batteries should best be stored only halfcharged.
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