# Tagged Questions

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### Boat; How to charge Leisure batteries the first time? [on hold]

I will have 4 x 12V 100ah leisure batteries for my boat. They will be wired in parallel(using staggered wiring). My alternator is 12V 50amps. The batteries will be charged when the boat is moving. ...
164 views

### Will a 6 volt LED kill a 9 volt battery quickly?

I am building a little circuit and I am adding a little 6 volt LED to tell me when I have power going through. But my power source is a little 9 volt battery, will this LED kill this battery quickly? ...
108 views

### Amplify current and voltage to preserve battery

I'm wondering, is it possible to provide for example 5V/500mA from a single 1.2V battery and consuming only 50mAh from the battery by using a low input voltage boost converter and a power amplifier ? ...
110 views

### Convert 48V battery bank to 12V for boat appliances - Inefficient?

I need a 48V bank for an electric motor on my boat. I also need 12V for my appliances. Obviously keeping both a 48V and 12V bank would be most efficient but the space required and cost of maintaining ...
88 views

### How to detect low battery under load?

I was measuring the voltage across a 12v VRLM battery when I noticed something : the battery had 11.7 volts without the load and when the load was added, the voltage dropped to 11.4. I don't want to ...
194 views

### What's the relationship between volts and amperes in batteries?

I recently bought a bag of 100 5mw 4.5V laser diodes (the spec said they have "driver: out"). My idea was to connect two and two of these in series to get something that needs 9V, and then connect ...
342 views

### Stabilize 12V to 12V

How can I stabilize a 12V input to a 12V stabilized output voltage? I have a battery that supplies 12V but not regulated and a device that uses 12V regulated, how can I supply power to that device ...
170 views

### How to reduce voltage from a battery to a motor [closed]

I have a 14.8v battery and I want to run a motor on 13v. What is the best solution to reduce the voltage from 14.8v to 13v?
113 views

### How to use a solar panel that has 'watts' to power a battery charger that requires: 3v & 2.8 amps?

I have a battery charger that charges small batteries ( AAA & AA ). It uses an adapter that gives it 3V and 2.8 amps. I want to remove the adapter and give it solar energy instead. There are ...
318 views

### How to power an Attiny from AA batteries?

I am working on a project where I would like to power an RGB Led in a ambient light situation. I have prototyped this using an Arduino Leonardo and the led. Currently the project is plugged into the ...
93 views

### If a battery was overused will the voltage decrease? [closed]

I have a 1.5V battery. When my battery is overused will its voltage remain the same or will it decrease?
105 views

### How to Calculate battery drainage from a set # of LEDs

I will be wiring 18 LEDs to three 3.7V batteries(600mAh) in parallel. 10 of the LEDs are rated at 4.5V with 40mA and 8 LEDs are rated 3V with 20mA, how long will these 18 LEDs run on the three ...
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### Low Voltage Disconnection

How to build a circuit wich operates on 12V DC Battry (which is used in multimeter) and it sense the DC Volatge Range from 56V DC to 44V DC on attaining 45V DC circuit send a Ground Signal through a ...
102 views

### How to measure battery charge and depletion over time

When using my various electronic devices, they always seem to know how much charge is left in the battery. They also know when the battery is completely charged. Not exactly sure how this is ...
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So if I have a batter that says it can produce a max of 2000mAh and a device that says it uses 3.6 mA does that mean I can run the device for 2000mAh / 3.6mA ? How does the voltage get factored into ...
124 views

### Mystery in extremely simple circuit [closed]

I have 3 pairs of wires from a battery, each pair goes to a lightbulb, two of them light up, I measure the voltage of the last pair as 10V, then I put a lightbulb in the third, and now the bulb doesnt ...
84 views

### Choosing the right batteries

I have a Radio control circuit for a boat I made and I don't really know which kind of batteries I have to use. Can someone explain me the differences (A, AA, AAA, C, D) and others if there are) and ...
228 views

### Single terminal of voltage source attached to earth ground

This is a conceptual question I continue to struggle with as I have started studying electronics. Say we have a battery, and one of its terminals is connected directly to a nice patch of highly ...
300 views

### Why is it bad to mix new and old batteries?

I've seen warnings that it's bad to mix new and old batteries -- why? Is it a matter of a battery's age or a battery's voltage/current (remaining)?
101 views

### Two questions about charge between capacitor plates

Let's say that we have capacitor with two identical plates - but one of them (let's call it plate A) is 50% of the size. Let's put a current through this capacitor so that there is some voltage V. ...
423 views

### Is a solar panel clamped to a battery a drain on the battery at night time?

I noticed that in the night time (dark) the voltage measurement on the battery was lower than in the day time (sun), measured with my voltmeter. I'm new to electricity, but that made me assume it had ...
217 views

### Why do batteries in series add up voltage?

This question will probably sound easy to most of you, but to me, it is still a kind of magic :) Taking in account all I know until know, I guess a battery has two sides: one that "emits" electrons ...
2k views

### Can I connect my laptop that runs on 18.5V directly to a 12V battery?

I have days of electricity outages here (due to war!!!) and I need to use my laptop. The thing is, it runs off 18.5V 3.5A (AC adapter output), so it is expecting 18.5V, what will happen if I connect ...
135 views

### Is it possible to amplify a sine voltage by a factor of 190? [closed]

I would like to amplify a sinusoidal wave (-1.23V to +1.23V) to a wave between -230V and +230V. I am planning to use a 12V@8.1Ah battery as my Vcc source. My question, Is this idea possible? If it ...
705 views

### Can you damage an iPhone by charging it using a (homemade) solar panel?

I found a guide online that shows how to make a solar phone charger (in a bottle), and I thought I'd try it out, but I'm worried about damaging my iPhone 4 (for a school project). (If anyone's ...
118 views

### Conversion of voltage of battery [closed]

I have 9 volts battery. What resistance do I need to have 5 volts. And how to calculate?
216 views

### Simple circuit Voltage regulator question?

I am trying to build a simple circuit that takes a 9v battery through a voltage regulator that outputs 1.5v across a load resistor . The load will be just a piece of metal that gets heated up. My ...
154 views

### Getting a higher voltage from a battery than specified

This may be a totally stupid question, but say I have a battery that supplies power at 7.5 V. Is there any way to boost its voltage to provide 9 V? I know you can step down voltages in many ways ...
125 views

### AA cells depletion

Currently I have two AA cells in series powering a 3.0v bus line for my application.Recently I am finding that one of these AA cells gets completely dead before the other. What could be the possible ...
494 views

### If my battery charger says 160mA on the back, what does that mean to my 1800mAh batteries?

I'm sorry if this is a horrible place to ask such a question. I just stumbled upon here from google. So I have this battery charger that DOES NOT indicate when a battery is fully charged (stupid ...
176 views

### Battery monitor gauge for embedded development

For one of our upcoming projects, we have a battery pack consisting of 12 Energizer L91(Lithium /Iron disulphide AA Battery). We divide this battery pack into three sets of 2 ,5 and 5. In order to ...
191 views

### Increase resolution of voltage divider

I have a lead-acid battery on which I am using a voltage divider to measure the remaining charge. Its my understanding that an example battery could discharge from 100-0% over say 10.5V - 12V. ...
225 views

### SPICE Modeling voltage during battery discharge

I am trying to create a spice model of a battery discharging into an LED. I would like to model the charge remaining (Ah) throughout the discharge and as I understand it this can be acheived by ...
379 views

### What's a good estimate on how low an alkaline battery voltage can be to still make the battery useful?

Here's a YT video by Duracell about how many batteries declared dead and sent to recycling still have some usable energy. In the beginning of the video there's a sequence where they have a row of ...
318 views

### Battery Power for RC Car

I'm working on a school group project which involves setting up a remote controlled car with a BeagleBone, webcam, WiFi module and a powered usb hub. To handle the mechanical side, we bought a cheap ...
169 views

### Connecting arduino to power another device

I have an arduino board which I want to use to give power to a device which uses two 1.5V batteries. I think I have to remove the batteries from the device and control the power supply via arduino, ...
667 views

### 3.7 Volt external battery to charge a another 3.7 Volt Phone Battery?

I would like to know if a 3.7 V external Battery would be able to charge a phone battery of the same voltage. From my understanding, the batteries would charge each other until the charge in both the ...
352 views

### Battery in parallel with main power source

I have a system that is powered by a main voltage supply and I want to connect it to a battery for backup, in case of power outage. I need to know what would happen if I connect the system with the ...
445 views

### Laptop power supplies - why the spectrum of voltages and connectors?

Why do are laptops designed with different Voltage input requirements? Is this just a power requirement consideration, or something more technical? Maybe the lithium battery requirements? (And - for ...
88 views

### which battery will supply the load?

I have connected 14V supply terminal from alternator to 12V battery terminal and has taken the load across these terminals . But the load is operating still in 12V, and when measured across the ...
655 views

### How to calculate consumed energy effects on battery voltage?

I have 2 3,6V batteries. I want to send a SMS when voltage drops down to 3,4V. I ve chosen a voltage detector which has a 3,4V threshold. What I am trying to figure out is how long does it take the ...
241 views

### How to best estimate power consumption for a system?

I'm not an engineer, I'm a software guy getting into hardware - so bear with my ignorance! I'm in the process of building a system with many components (e.g. a computer, many sensors, a few motors, a ...
150 views

### dying battery, increasing resistance

this is a graph of v-i relationship of a battery (not ideal one since it has internal resistance) as you can see, the slope is 1/R, so as time passes by, R increases, therefore, the slope ...
526 views

### Arduino Mega run on 2 AA batteries? [closed]

I am completely new to electronics and I have a question. I read that the Arduino Mega runs on 5V and that a supply of 6-12V is recommended for stable operation of the board. So what if I wanted to ...
841 views

### How does a battery recharge?

Alright, I should probably know this, but I don't. For a school project, I need to be able to charge a 12v battery from an alternator. What I am stuck on is the method of how batteries (generally ...
248 views

### How to provide stable power to RF receiver when operating on small batteries with blinking LEDs

I have a very simple circuit design (simple to keep cost low) consiting of a super-regenerative (or super-heterodyne) RF receiver, a Microchip PIC and 3 LEDs. These are powered on 3 or 4 AG13 ...
753 views

### 19v Charger with 14.4v Battery: What exactly can I expect?

Long story short: I have to replace the charger AND battery on my ASUS U53F-BBL5 laptop due to a combination of lost original charger and Best Buy can't read a laptop's model number for the correct ...
2k views

### Why is there risk of overvoltage when jump-starting a vehicle?

Ford Focus C-Max manual describes jump-starting procedure as follows: shut off everything, connect the jump cables, start the donor vehicle engine and let it run for a while, turn the ignition key on ...