A device for protecting 12v batteries from deep discharge and short circuit with automatic disconnection of its output from the load.
CHARACTERISTICS
The battery voltage at which the shutdown occurs is 10± 0.5V. (I got exactly 10.5 V) The current consumed by the device from the battery when turned on is no more than 1 mA. The current consumed by the device from the battery when turned off is no more than 10 µA. The maximum permissible direct current through the device is 5A. (30 Watt light bulb 2.45 A - Mosfit without radiator +50 degrees (room +24))
The maximum permissible short-term (5 sec) current through the device is 10A. Turn-off time in case of short circuit at the device output, no more than - 100 μs
OPERATING ORDER OF THE DEVICE
Connect the device between the battery and the load in the following sequence:
- connect the terminals on the wires, observing the polarity (orange wire + (red), to the battery,
- connect to the device, observing the polarity (the positive terminal is marked with a + sign), the load terminals.
In order for voltage to appear at the output of the device, you need to briefly short-circuit the negative output to the negative input. If the load is powered by another source besides the battery, then this is not necessary.
THE DEVICE OPERATES AS FOLLOWS;
When switching to battery power, the load discharges it to the response voltage of the protection device (10± 0.5V). When this value is reached, the device disconnects the battery from the load, preventing further discharge. The device will turn on automatically when voltage is supplied from the load side to charge the battery.
If there is a short circuit in the load, the device also disconnects the battery from the load. It will turn on automatically if a voltage of more than 9.5V is applied from the load side. If there is no such voltage, then you need to briefly bridge the output negative terminal of the device and the negative terminal of the battery. Resistors R3 and R4 set the response threshold.
Spare parts
1. Mounting board (optional, can be mounted)
2. Any field-effect transistor, select according to A and B. I took RFP50N06 N-channel 60V 50A 170 deg
3. Resistors 3 for 10 kΩ, and 1 for 100 kΩ
4. Bipolar transistor KT361G
5. Zener diode 9.1 V
Add. You can use terminals + Mikrik for starting. (I didn’t do it myself because it will be part of another device)
6. You can have an LED at the input and output for clarity (Select a resistor, solder in parallel)
Soldering iron + tin + alcohol rosin + wire cutters + wiring + multimeter + load, etc. and so on. Soldered using the tin-nozzle method. I don’t want to poison the board. There is no layout. Load 30 Watt, Current 2.45 A, the field worker heats up at +50 degrees (room temperature +24). No cooling needed.
I tried a load of 80 watts... VAH-VAH. Temperature over 120 degrees. The tracks began to turn red... Well, you know, you need a radiator, Well-soldered tracks.
DEVICE for protecting 12v batteries from deep discharge and short circuit with automatic disconnection of its output from the load.
CHARACTERISTICS
The voltage on the battery at which the shutdown occurs is 10± 0.5V. (I got exactly 10.5 V)
The current consumed by the device from the battery when turned on is no more than 1 mA
The current consumed by the device from the battery when turned off is no more than 10 µA
The maximum permissible direct current through the device is 5A. (30 Watt light bulb 2.45 A - Mosfit without radiator +50 degrees (room +24))
The maximum permissible short-term (5 sec) current through the device is 10A
Turn-off time in case of short circuit at the device output, no more than - 100 μs
OPERATING ORDER OF THE DEVICE
THE DEVICE OPERATES AS follows:
Spare parts
2. Any field-effect transistor, select according to A and B. I took RFP50N06 N-channel 60V 50A 170 deg 3. Resistors 3 for 10 Ω, and 1 for 100 Ω
5. Zener diode 9.1 V
Soldering iron + tin + alcohol rosin + wire cutters + wiring + multimeter + load, etc. and so on
Soldered using the tin-nozzle method. I don't want to poison the board. There is no layout.
Load 30 Watt, Current 2.45 A, the field worker heats up to +50 degrees (room temperature +24). No cooling needed.
I visited a load of 80 watts... VAH-VAH. Temperature over 120 degrees. The tracks began to turn red... Well, you know, you need a radiator, Well-soldered tracks.
Communities › Electronic Crafts › Blog › Protecting the Battery from Deep Discharge…
Tags: battery protection, battery, 12v, 12v, 12v, 12v, protection, recorder, mosfit. Protecting the Battery from deep discharge... The circuit is not mine. I’ll just repeat... Use where necessary... Recorders, tape recorders, etc. ... DEVICE for protecting 12v batteries from deep discharge and short circuit with automatic disconnection of its output from the load. CHARACTERISTICS Battery voltage...
Hi all. I recently assembled an electronic switch based on a field-effect transistor that automatically turns off the battery when discharged to a specified voltage. That is, this device is capable of monitoring the decrease in voltage on the battery and disconnecting it from the load in time so that it does not go to zero and deteriorate. For example, if you forgot to turn off the flashlight.
Battery protection device diagram
For lead-acid batteries with a voltage of 12 V, the minimum permissible voltage during discharge is approximately 9 V. It is at this voltage that the load must be disconnected from the battery in order to prevent it from being deeply discharged. It is convenient to control the battery voltage using the TL431 parallel stabilizer chip. This chip contains a built-in error amplifier and a precision voltage reference. To switch the load, it is recommended to use a MOSFET transistor, which can provide a very low on-state voltage drop. The scheme is extremely simple, I used it myself for several years, having assembled it using a hinged installation, and only recently made a “boxed” version:
In this version, the switch is for 6/12V batteries, P1 is selected and then replaced with permanent ones. For 6 V – the threshold is 4.8..5 V, for 12 V – 9.6..10 V, respectively. You can set your P1 for other cutoff voltages if desired. For convenience, I added an indicator - LED.
In view of the shortage of powerful P-channel field-effect transistors, and even “Logic Level”, the circuit can be converted to an N-channel one, instead of the P-channel one, installing a low-power P-N-P transistor of the KT316 type, and this can be used to switch the powerful N-channel one key. But in this case, it is not the “plus”, but the “minus” of the load that will be disconnected.
A radiator is not required for load currents up to several amperes - this is accurate, verified. In general, for installation in a car, where currents reach tens of amperes, everything is easy to calculate. We multiply the resistance of the open field switch by the squared current.
And although the transistor does not heat up at all, I still installed it on a small radiator, just to be on the safe side. There was just one case when, during the process of recharging the battery, I touched a field worker - it was noticeably hot. While figuring out what was going on, I found out that the 431st stabilizer had failed, and the key was “stuck” in linear mode, never fully opening – which was why it was heating up. Why the stabilizer burned out remains a mystery, it was soldered, maybe it had already happened before. All other elements of the circuit remained intact.
Battery deep discharge protection
Protection against deep battery discharge Hello everyone. I recently assembled an electronic switch based on a field-effect transistor that automatically turns off the battery when discharged to a specified voltage. That is
A device for protecting 12v batteries from deep discharge and short circuit with automatic disconnection of its output from the load.
CHARACTERISTICS
The battery voltage at which the shutdown occurs is 10± 0.5V. (I got exactly 10.5 V) The current consumed by the device from the battery when turned on is no more than 1 mA. The current consumed by the device from the battery when turned off is no more than 10 µA. The maximum permissible direct current through the device is 5A. (30 Watt light bulb 2.45 A - Mosfit without radiator +50 degrees (room +24))
The maximum permissible short-term (5 sec) current through the device is 10A. Turn-off time in case of short circuit at the device output, no more than - 100 μs
OPERATING ORDER OF THE DEVICE
Connect the device between the battery and the load in the following sequence:
- connect the terminals on the wires, observing the polarity (orange wire + (red), to the battery,
- connect to the device, observing the polarity (the positive terminal is marked with a + sign), the load terminals.
In order for voltage to appear at the output of the device, you need to briefly short-circuit the negative output to the negative input. If the load is powered by another source besides the battery, then this is not necessary.
THE DEVICE OPERATES AS follows:
When switching to battery power, the load discharges it to the response voltage of the protection device (10± 0.5V). When this value is reached, the device disconnects the battery from the load, preventing further discharge. The device will turn on automatically when voltage is supplied from the load side to charge the battery.
If there is a short circuit in the load, the device also disconnects the battery from the load. It will turn on automatically if a voltage of more than 9.5V is applied from the load side. If there is no such voltage, then you need to briefly bridge the output negative terminal of the device and the negative terminal of the battery. Resistors R3 and R4 set the response threshold.
Spare parts
1. Mounting board (optional, can be mounted)
2. Any field-effect transistor, select according to A and B. I took RFP50N06 N-channel 60V 50A 170 deg
3. Resistors 3 for 10 com, and 1 for 100 com
4. Bipolar transistor KT361G
5. Zener diode 9.1 V
Add. You can use terminals + Mikrik for starting. (I didn’t do it myself because it will be part of another device)
6. You can have an LED at the input and output for clarity (Select a resistor, solder in parallel)
Soldering iron + tin + alcohol rosin + wire cutters + wiring + multimeter + load, etc. and so on. Soldered using the tin-nozzle method. I don’t want to poison the board. There is no layout. Load 30 Watt, Current 2.45 A, the field worker heats up at +50 degrees (room temperature +24). No cooling needed.
I tried a load of 80 watts... VAH-VAH. Temperature over 120 degrees. The tracks began to turn red... Well, you know, you need a radiator, Well-soldered tracks.
Protection of batteries from deep discharge
Battery protection from deep discharge A device for protecting 12v batteries from deep discharge and short circuit with automatic disconnection of its output from the load. CHARACTERISTICS
How often do we forget to turn off the load from the battery... Have you ever thought about this question... But it often happens that the battery seems to be working and working, but then something has dried up... We measure the voltage on it, and there is 9-8V, or even less. Torba, you can try to restore the battery, but it doesn’t always work.
For this reason, a device was invented that, when the battery is discharged, will disconnect the load from it and prevent deep discharge of the battery, because it is no secret that batteries are afraid of deep discharge.
To be honest, I thought many times about a device for protecting the battery from deep discharge, but it was never my destiny to try everything. And over the weekend I set a goal to make a small protection circuit
Battery protection circuit from full discharge
Any Start and Stop buttons without fixing
Let's look at the diagram. As you can see, everything is built on two op-amps switched on in comparator mode. LM358 was taken for the experiment. And so let's go...
The reference voltage is formed by the R1-VD1 chain. R1 is a ballast resistor, VD1 is a simple 5V zener diode, it can be used for higher or lower voltage. But not more and not equal to the voltage of a discharged battery, which by the way is equal to 11V.
A comparator was assembled on the first op-amp, comparing the reference voltage with the battery voltage. The voltage to the 3rd leg is supplied from the battery through a resistor divider, which creates the compared voltage. If the voltage on the divider is equal to the reference one, a positive voltage appears on the first leg, which opens the transistors, which are installed as an amplifier stage, so as not to load the output of the op-amp.
Everything is set up simply. We supply 11V to the Out terminal. It is on this leg, because the diode drops by 0.6V and then you will have to rebuild the circuit. A diode is needed so that when you press the start button, the current does not go to the load, but supplies voltage to the circuit itself. By selecting resistors R2R6, we catch the moment when the relay turns off, the voltage on the 7th leg disappears, and on the 5th leg the voltage should be slightly less than the reference
When the first comparator has been built, we apply 12V voltage, as expected, to the Vcc terminal and press Start. The circuit should turn on and operate without problems until the voltage drops to 10.8V, the circuit should turn off the load relay.
Press Stop, the voltage on the 5th leg will disappear and the circuit will turn off. By the way, it is better not to set C1 to a higher value, since it will take a long time to discharge and you will have to hold the STOP button longer. By the way, I haven’t yet figured out how to force the circuit to turn off immediately if there is a good capacitance on the load itself, which will take longer to discharge, although you can throw a ballast resistor on the condenser itself
At the second Op, it was decided to assemble an indicator indicating when the battery is almost discharged and the circuit should turn off. It is configured in the same way... We supply 11.2V to Out and select R8R9 to ensure that the red LED lights up
This completes the setup and the circuit is fully operational...
Good luck everyone with your repetition...
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Author of the Article: Admin check
Deep discharge battery protection device
How often do we forget to turn off the load from the battery. Then we measure the voltage on it, and there it is 9-8V. Khan to him Here is a device that will prevent the battery from completely discharging
Submitted The circuit protects the battery from deep discharge(discharge below the minimum permissible voltage) or disconnects the load from the source when the voltage drops. After the battery is discharged to the minimum supply voltage, the device disconnects the load from the battery. Suitable for protecting batteries such as lead-acid (Pb), NiCd, NiMH, Li-Ion and Li-Pol batteries.
The threshold voltage is determined by the sum of the voltages on the zener diode ZD1, the b-e junction of transistor T1 and resistor R1. To start the circuit, you must press the TL1 button. As long as the battery voltage is high enough, T1 and T2 are open. As the voltage decreases, current stops flowing through the zener diode and transistors T1 and T2 close. T2 operates in switching mode, so there is no slow gradual closing of the transistor.
In Fig. 2 you can see a modified circuit where the TL1 button allows you to turn the load on and off. The device thus serves not only as protection, but also as a power switch.
The maximum input voltage depends on the maximum voltage VGS transistor T2. The minimum input voltage depends on the voltage at which T2 still opens reliably. Typically, for MOSFETs this is about 5V; low voltage logic MOSFETs can operate at lower voltages. This allows the circuit to be used to work with Li-Ion / Li-Pol, which has a min. voltage is approximately 3.4 V. At low voltages, the Zener diode ZD1 can be replaced by a combination of diodes connected in series.
I tested the circuit with IRF3205 and IPB06N03LA depending on T2. Note: It is advisable to connect a fuse in series with the battery, otherwise there is a risk of fire if it fails.
Rice. 1 - Schematic diagram of battery protection from deep discharge (reduced).
I wanted to solder something... Don’t deny yourself such pleasure :)
The background is this. I’m assembling a quadcopter :) I need good batteries: large capacity, good current output, lightweight. Those. lithium-ion. A couple of batteries were purchased and it was decided to test them. Lately I have been checking everything I buy in China. It is much better to assemble the device from known good parts: firstly, there is time to re-order the part if it arrives dead, and secondly, it is easier to check the element on the table than in the device and you will not have to rip it out of the bowels if something happens. Input control is correct!
So, I check my batteries and find that they show a capacity noticeably less than declared. Well, it happens that they lay in a warehouse and all that (although the voltage was normal and this should have raised alarm bells). I remember that batteries can be “trained”, i.e. carry out several discharge-charge cycles and then the capacity can be restored.
I put one battery on the iMax B6 charger, which can automatically control the discharge and charge processes. The process is long... what to do with the second one? Yeah, a thought! Let me light it up the old fashioned way, with a light bulb! Yes, I know that lithium-ion batteries cannot be discharged below about 3 Volts per cell (“cell”), but I have a tester, I will monitor the voltage directly at the balancing connector... In general, a bad idea. Of course, I got carried away and drained the battery to zero 🙁
I thought it was no big deal. Past experience with nickel-cadmium suggests that full discharge is bad, but not fatal. But no! My battery only needed one time for one cell out of three to swell and die (I had to amputate it and now I have a 2S battery). Those. It’s not just impossible to discharge a lithium-ion battery below 3V per cell, but completely, completely impossible!
So, we think further. Not all devices, especially homemade ones, have a controller that will prevent the battery from being discharged to a dangerous level. This means that you need some kind of device that will monitor the voltage and warn if something happens. Modelers all over the world are laughing out loud at me for such a fresh idea 😀
How to do it? The thought flowed into some damp distances, towards a circuit on a microcontroller with element-by-element control of the battery... And then a video caught my eye, in which a very simple analog circuit was proposed that turns off the power when the voltage drops below a given threshold. True, it only monitors the overall voltage on the battery and does not control individual “banks”…. but we charge our battery honestly, on a balancing charger, so when working it is enough to know the total voltage.
While I'm thinking, the Chinese are acting! And then one of them screwed up, instead of the ordered “crank” (L7805), he sent powerful MOS transistors (aka MOSFETs). Well... since so many things have come together, it’s time to take up the soldering iron :)
Yes, the scheme is valid. But there is a nuance (c). It has a start button. Those. To turn on the load, you need to apply voltage and briefly press the button. Inconvenient: two actions instead of one. I want it without a button!
When creating self-powered devices, care must be taken to protect the battery from deep discharge. It is enough to miss the moment once and allow a deep discharge of the battery below the minimum voltage threshold and your battery will fail, or will lose part of its capacity and will be unable to operate at rated load currents.
In order to prevent cases of voltage drop below a critical level in the open circuit of the battery-consumer, protection circuits are installed, which consist of several units:
comparator and power switch.
Requirements for the protection circuit:
- low leakage current (self-consumption)
- switching currents comparable to the maximum permissible for the battery
This battery deep discharge protection circuit was assembled to protect a 6 volt acid-gel battery with a capacity of 4 ampere-hours, but it can also be configured to work with 12 volt batteries and higher, up to the supply voltage of the ne7555 chip. The prototype of this board was found in some magazine and slightly modified. Instead of a conventional zener diode, an adjustable zener diode TL431 was introduced, which allows you to adjust the cutoff voltage (load disconnection) in conjunction with adjusting the resistive divider R6/R7. From the 3rd leg of the 555 timer chip, the signal began to not illuminate the LED, but to open the n-p-n transistor, which in turn opens the power switch N-channel field-effect transistor. Pay your attention to the characteristics of this transistor, it must be designed to work with the expected load currents, and another important detail is gate opening voltage. If you are planning a circuit for a 6-volt battery, you need a field-effect transistor with an opening voltage of 5 volts n-channel logic level mosfet. Field-effect transistors for “general power” purposes with an opening voltage of 10-20 volts will not suit you, since with a voltage between the gate and source of the transistor of 5 volts, they will not be in saturation mode but in linear mode, which will lead to strong heat generation and failure .
