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Questions tagged [batteries]

An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy

298
votes
6answers
63k views

Why is there so much fear surrounding LiPo batteries?

I've been trying to design a charging system for a small robot powered by a 2S 20C lithium polymer (LiPo) battery. Were I to trust everything I read online, I would believe that the LiPo will kill me ...
12
votes
3answers
16k views

Measure Lithium ion battery voltage (thus remaining capacity)

What I am working with: I am running my self-made Arduino board (in the sense that I use the Arduino bootloader and code editor) at 3.3V, and powered from a Lithium ion battery, which is USB-charged ...
87
votes
5answers
231k views

Why are there 3 pins on some batteries?

Lots of new batteries (for mobile devices, MP3 players, etc) have connectors with 3 pins. I would like to know what is the purpose of this and how should I use these three pins? They are usually ...
8
votes
4answers
37k views

Battery Ampere-hour rating vs Battery Amps (not an experienced user)

I have almost no experience whatsoever with the technicals of electronics so this is probably a very easy question for someone who does. Do you know if a battery with a 200Ah rating can put out 200A ...
6
votes
6answers
33k views

Charging Li-ion batteries in parallel

I wanted some opinion on my set up here, just to make sure I got the basics right. I have a Li-ion battery charging circuit based on the MCP73113. This is designed to be a single-cell battery charger....
1
vote
1answer
573 views

What kind of power management circuit do I need to embedded a rechargeable battery in my electronics project?

I am doing a project where my electronics runs on 5V which I wanted to power from a 7.2v lipo regulated down to that voltage. I'd really like to include the opportunity to charge the lipo without ...
2
votes
1answer
8k views

Troubleshooting why Powerbank Doesn't Charge Cell Phone

I have powerbank that provides 5v (presumably regulated) power, as typical of most usb interface powerbanks. I have been trying out my powerbank with different phones. It works on all except one. I ...
21
votes
6answers
261k views

How to Calculate the time of Charging and Discharging of battery?

How do I calculate the approximated time for the Charging and Discharging of the battery? Is there any equation available for the purpose? If yes, then please provide me.
42
votes
3answers
36k views

When a battery is your power source, what is ground?

For the sake of not incorrectly connecting my power supply and damaging my board I'm going to ask a relatively dumb question. Is ground on my board the negative terminal on my battery? Explicitly ...
28
votes
5answers
4k views

Charging lead-acid batteries?

Are there any special requirements for charging lead-acid batteries?
16
votes
4answers
9k views

Pulse-powering heavy loads with a coin cell

Lithium coin cells are rated for fairly low standard current draws, on the order of 1 to 5 mA. Also, while they allow greater pulsed current draws (i.e., periodic bursts), this appears to be ...
6
votes
2answers
26k views

Powering 10watt light bulb for 24 hours using solar power

I am a total noobi to solar power and even electricity so I apologize if I am asking a silly question. Imagine I have a 10 watt light bulb which I want to leave on for 24 hours a day. Will I just ...
31
votes
2answers
12k views

How to calculate battery life

How do I calculate how long a battery operated product will run? Here's what I've got: 2 AA, 1.5V, 2700mAH batteries Voltage Regulator with a Iq of 25 uA Voltage Regulator Eff = 80% Active Current = ...
19
votes
2answers
60k views

Adding mAh when wiring battery cells in series?

When combining battery cells in series, the voltages of the cells are added to get the voltage of the final circuit. Do the mAh add up, or stay the same? For example, suppose you have two 3.7V cells,...
13
votes
2answers
5k views

Calculate battery life

I would like to know how to calculate battery life when using an LED strip. The LED strip is powered by 8 AA batteries in series. LED Current Draw = 260 mA. LED power consumption: 3.1 W. LED Operating ...
20
votes
5answers
24k views

Whats does “hr” mean among “V” and “Ah” in batteries?

I have a battery which indicates 12V25Ah/10hr. What does 10hr mean here? I guess "hr" stands for "hour". But 25Ah already means if battery is fully charged and if I load 12V 25A (=300W) to it, it ...
1
vote
3answers
423 views

Actual electric potential at terminals of battery

I understand that a 9V battery will produce an electrical potential difference/voltage of 9v across the positive and negative terminal, with the positive terminal having the higher potential by ...
60
votes
4answers
297k views

Does mAh measure how long a battery would last?

I know mAh tells how much milliamperes a battery can deliver in an hour. But does that also tell how many hours the battery would last? Sorry but I don't really get it. If we're talking about a water ...
22
votes
3answers
32k views

Why are deep cycle batteries rated in amp hours instead of watts hours?

Why are deep cycle batteries rated in amp-hours instead of watt-hours? For example if I see a 85Ah battery, I multiply 85Ah x 12V to get 1020 watts. As household electricity use is measured in watt ...
25
votes
3answers
4k views

Why do batteries recover after a load is removed?

I carry a small 2-AA flashlight, and a few times, I have accidentally left it on in my holder. Each time it dies completely, so that no light is emitted, but if I turn it back off and wait for a few ...
16
votes
2answers
4k views

How fast can a Li-Ion battery be charged?

So far I've seen many Li-Ion battery chargers that do the full charge in about 1,5 hours or more. There're also NiMH battery chargers that claim they charge a NiMH battery in 15 minutes and then the ...
6
votes
6answers
19k views

Wrong multimeter readings measuring 12V lead acid battery

I just got my first multimeter and when I measured a 12V 1.2ah lead-acid battery I get AC 28.8V and DC 13.4V. Is this normal? In addition I tested an AA 1.5V battery and I got 2.9V (AC setting 200) ...
20
votes
3answers
28k views

Batteries in series with different amp-hour ratings.

I have a 1.5 amp-hour, 12 V battery and I have a 10 amp-hour 12 V battery. I know the voltage will increase to 24 V when they are put in series, but I don't know what goes on amp-hour wise. Does the ...
32
votes
5answers
53k views

Regulated 3.3V from a Lithium-ion (or LiPo) battery

Background I wish to power my circuit with a Lithium-ion or LiPo battery (likely a battery with around 1000 mAh capacity). These batteries have a voltage that goes from 4.2V to 2.7V typically during ...
26
votes
4answers
135k views

How to measure capacity of a Lithium-ion battery

I bought a Lithium-ion battery for a camera (much cheaper than the brand replacement but non unreasonably cheap compared to AAA Li-Ion batteries with similar charge). I however have doubts that it has ...
10
votes
5answers
8k 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 ...
34
votes
3answers
28k views

How is wristwatch with 10 years battery life possible?

Turns out Casio offers a handful of wristwatches with "10 year battery life". The claim is that thanks to "an advanced technology" the battery life in those watches is extended to ten years. Now if ...
8
votes
5answers
4k views

How much can I overcharge a 4.35V LiPo?

I'm building a charger for a set of LiPo cells. My circuit needs to make sure they get fully charged to their maximum level of 4.35V. At the same time, the circuit should protect the cells from ...
2
votes
2answers
4k views

Can I charge and discharge a NiCd/NiMh battery at the same time?

I presume there will be opposite movements of the charged particles inside, with collision energy being exhaust as heat. On the other hand, such a setup would probably introduce an extra noise/...
1
vote
1answer
357 views

Trying to Get the Most Cooling Power out of TEC Peltier Element: Smaller or Larger Peltier?

I am trying to achieve the strongest cooling effect using a TEC Peltier element. Currently, my set up is two small, 20mm x 20mm peltier TES1-4902 run with a 5V 2.4A USB Battery Pack per peltier. I ...
-6
votes
3answers
2k views

A capacitor stores half the energy when charged from a battery each and every time? [closed]

I understand that when a battery is connected to a capacitor that half the energy is stored in the capacitor while the other half is lost to heat or whatever other losses are involved once the ...
26
votes
7answers
26k views

Least expensive way to boost DC voltage

What would be the least expensive way to boost a DC voltage? The aim is to convert 1.2 V/1.5 V (from an AA/AAA cell) to 3.3 V to power a small 8-bit microprocessor, like Atmel ...
36
votes
5answers
10k views

Are decoupling capacitors needed with battery power?

Currently I run all my gadgets from batteries and don't use decoupling capacitors. Are they generally needed/useful when drawing energy from a battery?
30
votes
8answers
41k views

Current flow in batteries?

I am reading a basic electronics book: "There are no Electrons: Electronics for Earthlings" and I came across a clever passage about the fact that you need a closed circuit in order for current to ...
20
votes
6answers
34k views

Why are batteries measured in ampere-hours but electricity usage measured in kilowatt-hours?

I was reading about energy usage in batteries and don't quite understand why it is measured in different units than home electrical usage. An ampere-hour does not include a measure of volts. But my ...
35
votes
4answers
79k views

At what voltage is a NiMH battery empty?

I have a battery pack of NiMH batteries. It is ten cells with 1.2V, 4000mAh each, put together in series. So rated voltage is 12V. After charging, i.e. when the charging device says that it is ...
14
votes
4answers
22k views

Least expensive way to plug in a microcontroller into 120V (without wall wart or batteries)

I need to be able to power a Atmega168 by plugging it into a wall. The circuit is a little bit more complex but not too much. The Atmega168 needs between 1.8V and 5V at 200mA. The ideal solution ...
6
votes
5answers
62k views

How to get high current from 9 volt batteries

I am planning to make a solenoid.. Which should be so powerful as to lift up about 600N force. I have thought about it, and I have a doubt. How can I get DC currents up to 20-30 A using a 9 V battery? ...
24
votes
3answers
14k views

Does leaving a cell phone on charge all the time weaken the battery, and why?

If I leave my cell phone with the charger plugged in all the time, would this weaken the batter, and why? I've heard that you should only charge the cell phone when you receive a 'battery low' message ...
16
votes
5answers
74k views

Powering laptop from 12V sources without inverter

This question has two parts: 1) How inefficient is it to boost 12V to 120V and then back to 12V as in using a traditional car power inverter to power a laptop (i.e. the 12V car battery power is ...
12
votes
1answer
916 views

How to power a widget, while the li-ion battery is charging?

I am in need of a way to charge a 3.7V li-ion cell (probably an 18650 type) from a 4.5V - 20V input. That's not a problem, there are plenty of (switching) battery chargers around with that kind of ...
5
votes
3answers
172k views

How long will this appliance run from a battery? [closed]

How long can I run a water pump which requires 12V and 50W from a 12V, 40Ah, 400A car battery? Can you explain how this was calculated?
10
votes
3answers
5k views

Watts - I think I'm getting free energy from a circuit?

Imagine I have a 10V battery with a capacity of 1Ahrs connected to a 100 Ohm resistor. I'll get 0.1A (V/R) at a power of 1W (current x voltage) for a total of 10hrs. As a watt is defined as J/s my ...
16
votes
5answers
32k views

How do I connect two identical batteries to increase the consumer lifetime?

If I've got a device that uses a single battery, and with that single battery, the device lasts an hour, and I want the device to last for two hours, I'm assuming I can wire two batteries up and it ...
9
votes
3answers
4k views

How deep should we discharge lithium batteries to maximise their lifetime?

Recently I posted an answer mentioning the very classic "lithium batteries like partial discharges, so design your system for limited depth of discharge". But then I wondered: with partial discharges, ...
3
votes
4answers
10k views

Charging 3 AAs in series

I'm currently repairing a project built by someone else and want to avoid tinkering with it as much as possible. I am looking to recharge 3 AA NiMH batteries (at 1.2v each), that are in series. I ...
2
votes
1answer
524 views

Low Current Battery Monitor Detail Question

I'm trying to design a circuit that will be running from a battery. I'm currently working on the part that detects the voltage and came across this question (and answers) here: It made pretty good ...
2
votes
1answer
1k views

Arduino Negative Voltage Reading with Positive Ground

I am trying to measure voltage & current off a solar charge controller from panel, battery & load simultaneously with my arduino. I have managed to achieve this by tying all the negatives ...
8
votes
1answer
3k 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 ...
6
votes
4answers
19k views

Building a USB charger for camping

I was looking into building a battery powered USB charger for camping. It occurred to me that car chargers are pre-built and run off 12 V. If I made a battery pack out of 8x 1.5 V batteries in series ...