# Tagged Questions

Involving or pertaining to a circuit or device that is intended to be operated with cells or batteries (as opposed to mains power, for example).

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### How many batteries are required for a 3.5 kVA inverter?

I am planning to buy a 3.5 kVA small industrial inverter, but I am not able to figure out how many batteries are needed for that. Please anyone help me out with details.
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### Understanding C20 value of lead battery for a low power circuit

I've developed a simple circuit using a Photon to send data to my database. It has to be a portable device and because of this I looked into lead batteries. My circuit runs on 5V and draws a maximum ...
181 views

### Powering AC Appliance with DC

I have an AC speaker set and it is plugged into an outlet. Then the outlet is put into a transformer where the transformer output is 17V 2.5A AC. Then from the transformer is put through a bridge ...
160 views

### Turning off IC's when not used in battery powered circuit

I'm building a small battery powered device which contains an ATTiny85 micro controller, a dual common anode 7 segment display and 2x595 shift registers to drive the 7 segment display. The device ...
49 views

### High current draw at start up of DC motor. How to understand if the battery can withstand it?

Suppose I have a solar powered plant like this one below: simulate this circuit – Schematic created using CircuitLab The solar panel charges the batteries and, when needed, the power is ...
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### CR2032 alternative for higher current [closed]

I'm designing a small battery powered circuit which will draw around 50mA for a millisecond every couple of seconds. I was planning on using a CR2032 coin cell but have recently learned that a coin ...
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### Can I replace D cell with AA cell in an electric train?

I have an electric train powered by 2 D cells. But they are quite cumbersome and I have only AA charger and a bunch of good quality AA rechargeable batteries. So I want to tweak my electric train and ...
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### Power a laptop from 12V Battery using DC-DC Step Up Circuit

I have following items 1) DC - DC Step Up Boost (150W) http://www.ebay.in/itm/131625051992 2) 12V 12Ah Battery (Sealed Lead Acid Battery) 3) LCD Lead-acid Battery Capacity Tester I charge my ...
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### Detect battery/cell's charge

I am building a portable device with Raspberry Pi and powered by 3 AAA batteries in series. I am trying to create a battery indicator with a LED: Green = Full power Orange = Half power Red = Low ...
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### Elegant non-mechanical way to switch on battery-powered device the first time

For a primary-battery powered device, that will be stored for a period of time before first use, what is the most elegant non-mechanical* way to switch it on for the first time, after which it will ...
101 views

### Implementing a low cost battery backup circuit for internal RTC in STM32F030R8

Extension of this question. Datasheet: http://www.st.com/resource/en/datasheet/stm32f030f4.pdf The micro-controller in question has an internal RTC module but no VBAT pin. As such, the only way RTC ...
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### Detect if connected battery is rechargeable

The device I am building can be powered by USB or 3xAAA batteries. While connected to the USB, the device will charge the batteries. But before charging the batteries, the device needs to make sure ...
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### RTC Battery Voltage Error; Non-Ideal Op Amp Error?

First post here from a hobbyist electronics guy so please bear with me. I'm happy to do whatever I can to improve my question for the community. For a bit of a backstory, I have a project that ...
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### How to run ammeter in low resistance?

I need to measure current in a small electromagnet powered off 3 x AAA batteries in series. This is the manual for my multimeter. When I run this multimeter in series and try to find the current, the ...
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### Use a PIR sensor with a boost converter

I bought some cheap pir sensors on amazon (I think they are called DYP-ME003 modules). Now I am trying to use them on a small board powered by only one coin cell or aa battery. As they only work with >...
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### Current increases when circuit resistance is increased while measuring black box device power consumption

The circuit is powered with 3V a battery and contains a black box device who's power consumption we're measuring with a shunt. The rated required voltage for the device is 3V. Whit a 1 Ohm shunt, the ...
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### Power supply ORing without ORing controller IC [duplicate]

The objective is to fallback on battery power if external supply (5V) is cut off. The ORing circuit should have as low voltage drop as possible when powered by the battery. The business end of the ...
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### Portable Speaker Powered by Battery and Power Supply Separately but Can Charge the Battery From the Same Power Supply [duplicate]

I'm building a portable speaker using a PAM8403 amp, 3.7v battery, and a battery charging module, all powered by USB input. What I want to do is be able to switch between 1) charging the battery ...
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### Measuring state of charge of a non rechargeable CR123A lithium battery

Is there a method (voltage, resistance, other...) of measuring leftover charge in a non rechargeable lithium battery? Background: I'm trying to get a general overview of power consumption for few ...
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### What is more power efficient: GPRS or SMS for a GSM sim Arduino application?

I have a GSM shield for my Arduino and am wondering the most power efficient way to receive and send data from and to the cloud. The specific project I am looking to accomplish is starting my car ...
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### Power switching peripherial parts by MCU

Using an MCU like from MSP430 series, it is possible to create circuits that runs from battery power for years in some standby mode (waiting for button or realtime clock alarm for example). However, ...
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### Arduino and GSM Module running on Li-primary batteries for years

For one of our projects we need to run an Arduino board + GSM module (SIM800C for example) for many years on batteries without recharging. The Arduino should be in power down mode for 99,99% of the ...
2k views

### Lithium Coin Cell CR2032 battery specifications

I am using a CR2032 battery module to operate a BLE 4.1 module. The BLE radio for communication takes around 3.5ma to 5ma of current. But when I look at the datasheet of the battery (https://cdn-shop....
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### How to connect these two led strings?

I've recently bought myself 2 sets of leds. Each set has 10 leds in a row powered by a solar panel which charges 2x 1.2V batteries. My question is what do I have to do when I want to have all of the ...
44 views

### Float charge heat dissipation of battery [closed]

I have a lead acid battery with specifications shown below. I wish to calculate the power & energy required to charge the battery from fully discharged. Constant current discharge (amperes) at ...
109 views

### How long should 8, 1.5V batteries last for?

I purchased a GPS tracker from Amazon and instead of wiring it to the car battery I would like to simply attach my own power battery pack. I am a complete noob when it comes to electronics and I ...
243 views

### What is the meaning of 25C?

I have a lipo battery of 11.1V,3s,5200mAH. What is the meaning of the 25C discharge current? How much current does it indicate? How do you interpret it?
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### LDO regulator below minimum input voltage

I'm designing a circuit that will run from 3V battery. The battery can get as low as 2V and I want to use it as much as I can. I'm using a PIC24 that operates with the integrated regulator for ...
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### 5v usb cable to power a 2AA Kitchen Scale [closed]

This is my first question and I'm a total beginner at this, so, please be kind :D I have a kitchen scale that eats up 2AA batteries every 2-3 days, so I thought to power it via a USB wall charger (...
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### How to efficiently power wireless sensor node from a 9V battery?

Context I have recently set out to add some wireless features to my entry-level smoke detector. Problem In order to achieve that, I will be adding a custom pcb embedding an ATmega328P and a ...
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### Does a motor really need all this circuit to run?

This is the pcb of an Ikea screwdriver, you can see I desoldered the 18650 battery, from B+ and B-, and desoldered the motor from the legs of the switch which is on the other side. So the circuit ...
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### How to charge a lipo battery inline with load

How do you charge a lipo battery while it's still connected to it's load (e.g. like all modern mobile consumer electronics) using an off the shelf lipo charger? I have an Accucell S60 battery charger ...
61 views

### ESP8266 servo controler

I am building a small application, that should be able to connect over wifi to server, pull some data and turn a connected servo accord the result. The system should be powered on battery. Is this ...
67 views

### Powering 5v LEDs with 6 or 12 volt batteries

I'm building an art piece that uses about 2000 RGB LEDs. They are WS 2812b LEDs, and I expect the normal draw to be around 200-300 watts. If all bulbs go full white at the same time, it could pull up ...
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### 2 Blue LEDS , in series or parallel/ optimal power resistor type of batteries compact area

I intend on making a project illuminating an acrylic transparent rod. drill holes on both sides and inserting Blue LEDS tight space wired in series or parallel what resistor value and perhaps small ...
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### how to differentiate the gnd audio to gnd of battery?

i'm new to the forum. I have some problem to Connect this device with one single battery. I think the problem is on the connection of the max4466 electret. It has a common ground and it make me ...
272 views

### Car stereo wired to computer power supply with backup battery to keep memory

This past Christmas I re-purposed an old Car Stereo and built a portable outdoor radio for my Dad. Ultimately what I wanted to do is have it to where it runs primarily off of a computer power supply (...
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### How to Power a Controller and Motor Driver off same 24V source

I am trying to find the optimum electrical design for my project. The project is a remote control vehicle that is moved by 2 DC motors, controlled by an arduino MC and powered by 2 X 12V 4Ah ...
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### How to determine whether I need ESD protection? (MOSFET H-Bridge)

I am designing a H-Bridge using IRLZ44N MOSFETs, IR2104 driver ICs and UF5401 diodes. The current circuit looks like this: It will be used on a battery powered device, so no real grounding ...
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### Powering a sensor with a battery

Basically I'd like to deploy a sensor temporarily for a period of about a month. The sensor communicates via a wireless protocol and sends a data packet about once every 5 minutes as far as I ...
122 views

### Can solar panel charging slow down the draining of phone battery? [closed]

I have made a solar panel charger, it consists of a 1.2 watt panel connected to a buck converter, then to the phone. Now, when I connect it, it charges the phone and in the battery settings it shows ...
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### Portable 5v power supply to duplicate wall wart

I've got a wifi device that works off of a 5v 2a wall wart. I need to walk around with it to get some signal strength ratings, so I am making it a portable power supply. However, the device won't ...
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### Dealing with different voltage needs on a battery driven low-power board

I'm going to design a small wireless sensor box for a weather station project. This involves: A sensor running at 3.0-3.6V (1mA) A MCU, running at 3.0-5.5V A 433MHz transmitter which takes about 6-...
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### How to determine the Solar-panel power requirement battery

I'm having a problem calculating the rated power requirement for my solar panel project. The panel will charge a battery that will power a 'micro' water pump. The power requirement for the pump is ....
209 views

### Wiring power supply, battery and charger for portable speaker

I'm planning to build myself a small portable speaker. I'd like to include a Li ion battery and a jack for an external 12V-ish power supply. I'd also like to add a jack that will be used to charge the ...
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### suggestions for solar charging battery-operated device

My battery-powered wireless device draws about 50mA @ 5V. I’m thinking of powering this off a 12V 7Ah SLA battery that is topped up with a small solar panel (12V, maybe 500mA or so). 12V to 5V will ...
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### What AC-to-DC adapter would I need to power two of these battery (3V) powered door contacts at once?

I'm new to electrical wiring. I understand circuits, soldering, and basic wiring in parallel / series but calculating and understanding draw, resistance, etc. is new to me. That being said, I have ...
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### Car battery capacity in colder countries

The capacity of the battery is affected when the temperature drops, particularly Lead-acid batteries. So how in cold countries this situation is solved. In this PDF about automotive batteries at low ...