Using the status of the LED’s the charge level of the battery is determined. We have used U1:A with Blue LED for 100% indication, U1:B with Green for 75%, U1:C with Yellow for 50% and U1:D with Red for 25% of charge level.
#Battery monitor circuits Activator#
Thus we obtained a output voltage of about regulated 5.1V from the battery.Ĭircuits Library - 220+ practical circuitsĪ quad Opamp IC LM324 was used as an comparator or activator for the charge indication LED’s.
#Battery monitor circuits series#
Once it is connected a 1N4733A a 5.1V, 1W Zener diode is used to regulate the voltage along with a series resistor R1 which controls the current flow through zener. Initially connect the battery for charge testing to the circuit. For easier understanding let’s analyze the circuit in a step by step manner. The Voltage measured to the corresponding charge levels forms very important reference to the above circuit. You can find these details in the datasheet of the manufacturer, almost all 12V batteries carries the same properties but datasheet is always worth looking for. Now for a typical 12V battery the voltage at various charge levels will be Voltage measured I am going to take a 12V Li battery and keeping it as an example, the design the battery charge indicator circuit is explained below. Let’s design a simple circuit to know the percentage of charge in a battery. Failure to that may cause the battery dead, so now you would’ve known that knowing the charge in the battery is very necessary to keep the battery alive. Li batteries should be used in such a way that always 20% of the battery’s charge is left before recharging it. Li batteries proves to be very useful source of power but for long lasting performance you need to look on to key parameters carefully. In fact you can build one with minimal components and little sweat. But its not necessary you have to buy one of these modules to use your Li battery in a effective way. These kind of indicators generally measures the voltage in the battery and indicate the charge by turning up any appropriate LED’s. All images and diagrams courtesy of yours truly.Battery charge indicator circuits are very useful modules for efficient use of the Li batteries.In the next page, we will examine the contruction and components of the circuit.Ĭontinue on to Battery Monitoring Circuit components and layout. In this project, an additional program is written for a separate PIC MCU to simulate the requesting of battery data from the BMC. This process is interrupt driven and triggered by an i2c "START" condition sent by the external device. Once the cell voltages are determined by the BMC, they will be read by external devices via the i2c protocol. Therefore the microcontroller ADC results from each cell will be scaled to reflect a range of values from 3.0-4.2 V.Ĭommunication between battery monitor and external MCU: For LiPo battery chemistry, it is important to not allow any individual cell to drop below 3.0 per cell (for both battery life and safety reasons). The resulting output of these differences will be sent to 4 analog input pins of a PIC microcontroller and measured against a reference voltage of 4.2V (4.2V is the maximum cell voltage for LiPo batteries). Our sampling technique wil involve using differential amplifiers (configured as subtractors) to measure the difference in voltage levels between each wire of the connector and the wire that proceeds it (in order of the series connection). For purposes of illustration, if we assume that the pack is at its nominal voltage, the wires of the JST-XH connector will have the following voltages values (with respect to ground of our monitoring circuit):įrom observation (and by measuring the voltages of each cell with respect to the black wire) you will notice that the individual cells are connected in series. This means that each cell (there are 4 cells in a 4S pack) will measure a nominal 3.7 volts. Using the battery shown above as an example, we see that the nominal voltage of the pack is 14.8 volts. This reference voltage will be connected to ground of the BMC. The black wire is connected to the negative terminal of cell #1 of the battery pack. Our primary method of doing this will be through differential amplifiers connected to the 5-pin JST-XH connector of the battery. Our goal here is to design a Battery Monitoring Circuit (BMC) that can sample the voltage of the individual cells in a 4s LiPo battery such as the one found here. Four Cell LiPo Battery Monitoring Circuit
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