691 votes
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Why is there so much fear surrounding LiPo batteries?

Every cell phone (as well as laptop and nearly everything with a rechargeable battery) uses LiIon/LiPo (essentially equivalent for the purposes of this discussion). And you're right: In terms of ...
metacollin's user avatar
  • 28.4k
103 votes

Batteries. Why use 9V?

A 400mAh 9V battery will last a year with a 40µA current draw. Now consider a smoke detector. It is low power analog circuitry, most likely drawing less than the 40µA figure above. If you wanted to ...
bobflux's user avatar
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92 votes
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Batteries. Why use 9V?

First a AA is not a battery.. it's a cell. A battery is a "battery" of cells, i.e. more than one cell. A 9V battery contains six 1.5V cells. Rip one apart and see. As for why we still use 9V ...
Trevor_G's user avatar
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87 votes

Why is there so much fear surrounding LiPo batteries?

To use Lipo batteries safely, you must treat them with the same respect you would anything that can store and rapidly release a large amount of chemical and/or electrical energy. The bigger the ...
Brian G's user avatar
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73 votes

Why are car batteries still so heavy?

So, obvious answer first: why do batteries still weigh 20kg? Because they're still the same lead-acid batteries. Simple as that. No other technology came near the low cost per Ampere (and ampere-...
Marcus Müller's user avatar
73 votes
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If I am measuring 2.3 V on a 1.5 V AA battery from Duracell, is my multimeter broken?

Most likely cause is that you need to replace the battery in your multimeter. When the battery is very weak, the voltage drops to the point where the internal reference can no longer maintain ...
Spehro Pefhany's user avatar
73 votes
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Why are so many batteries 3.7V?

The voltage is dependent on the materials used in the cell chemistry and cannot be chosen per se. 3.7V is typical for Lithium chemistries. Similarly, 1.2V is typical for nickel-cadmium (NiCd), 1.2V ...
DKNguyen's user avatar
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65 votes
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Why are car batteries still so heavy?

So, now after the answer to your literal question to your real question, that you sadly didn't ask Battery technology has moved so far in the last 100 years. The lead-acid starter battery became ...
Marcus Müller's user avatar
63 votes

Supercapacitors as car batteries

It is not practical. I do not know why people do this, there is no benefit whatsoever. It amounts to misuse of something useful. Simply put, those videos are by people who don't know what they are ...
metacollin's user avatar
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58 votes
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Wouldn't charging a lithium battery to 80% only defeat the purpose of putting the battery into longer use in the first place?

When you run, you cover less distance by sprinting for a short time compared to running at marathon pace. Same goes for batteries. The longevity of Li-ion batteries is greatly affected by a) how deep ...
Mister Mystère's user avatar
57 votes

Why is there so much fear surrounding LiPo batteries?

When a big company wants to make a LiPo charger, they can: A. Have experts on staff and do extensive testing to make sure the charger will work safely across the full range of operating conditions. ...
Adam Haun's user avatar
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57 votes
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Can this battery be charged?

It's a lead acid battery. The second bullet point wraps to the third line (terrible layout). Do not charge in a gas-tight container In other words, you can charge it, just ensure that it can ...
JYelton's user avatar
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56 votes

How do we know that voltmeters are accurate?

These days, you build a primary voltage standard from a bunch of Josephson junctions and a microwave source. That generates a voltage that's dependent only on the defining constants of the ...
TimWescott's user avatar
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53 votes

Why can't I power everything with a 9 V DC battery?

Archimedes said, “Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.” This is the nature of the thought exercise you’re asking. And the answer is, yes, given a ...
hacktastical's user avatar
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51 votes
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Why do capacitors have less energy density than batteries?

This is more of a chemistry question, but the basic idea is, well, chemistry. A capacitor imposes an electric field around a dielectric, which can only store energy until it breaks down (typically a ...
Tim Williams's user avatar
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50 votes
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What is the truth about 1.5 V "lithium" cells?

Lithium batteries come in many different chemistries, and it is the chemistry that governs the voltage. The most common chemistries are on the order of 3-4V, but there are chemistries which have a 1....
Tom Carpenter's user avatar
45 votes
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12 V car battery short circuit with a wrench that has resistance of 0.5 ohms, how much current?

A wrench does not have a resistance of 0.5 ohms, it's way lower. Your basic multimeter cannot measure resistances to better than an ohm or so, the resistance of leads, and the unreliability of ...
Neil_UK's user avatar
  • 165k
43 votes

Why is there so much fear surrounding LiPo batteries?

[Though this late answer may get little exposure now that the question has exited the hot-list, I think it is essential to further emphasize the contrast between the comprehensive safety features in ...
Bill Dubuque's user avatar
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43 votes
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Watts - I think I'm getting free energy from a circuit?

Congratulations for having the wit to know something was wrong! simulate this circuit – Schematic created using CircuitLab Figure 1. Parallel and series arrangements of batteries will have the ...
Transistor's user avatar
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43 votes
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Current at 12 and 230 volts

Case 1: Using a 12 V - 1 kW heater. The heater draws 83.33 A from the battery. Case 2: Using a 230 V - 1 kW heater and an inverter. The heater draws 4.35 A from the inverter which, in turn, draws 83....
vu2nan's user avatar
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42 votes
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The voltage drops measured across very high value resistors do not add up - why is that?

Your meter is affecting the measurement Your voltmeter is also connected to the circuit, and in a different position for each of your two measurements. A "perfect" voltmeter would have an infinite ...
Jack B's user avatar
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42 votes
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Why do cordless tool batteries have a circuit board connected?

The circuit board is, most likely, a battery management system to ensure that batteries are charged in a balanced fashion. When each cell reaches a predetermined voltage (indicating sufficient charge ...
Transistor's user avatar
  • 175k
41 votes

Lithium Coin Cell CR2032 battery specifications

I did my PhD thesis on energy management in wireless sensor networks and was working with sensor nodes using CR2032 batteries. We designed the nodes ourselves (my supervisor designed the PCB and I ...
lowtech's user avatar
  • 511
41 votes

Is it safe for a CR2032 coin cell to be in an oven?

So, first of all, CR2032 is a Lithium Battery type, so, yes, overheat it and it has a good chance of exploding/combusting. I'd really just go and use some cable to get the sensor into your oven, and ...
Marcus Müller's user avatar
40 votes

Batteries. Why use 9V?

Boost circuits have a quiescent current; some energy is wasted simply by having the boost converter. They also get very inefficient at low duty cycles. So if you have a circuit that usually draws a ...
pjc50's user avatar
  • 46.7k
40 votes

Why are multimeter batteries awkward to replace?

The internals of a well designed handheld multimeter are designed to contain any explosions that may occur from failing parts. Imagine the following situation: you're holding a meter in your hand, ...
Hearth's user avatar
  • 31.8k
38 votes

Why can I use P = I²R but not P=V²/R when calculating energy lost in a circuit?

The problem assumes you understand something that is not clearly spelled out: the wires and the (unknown) load are in series. Therefore they share the current, not the voltage of the battery. That's ...
LorenzoDonati4Ukraine-OnStrike's user avatar
37 votes
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Why can't I power everything with a 9 V DC battery?

Batteries are chemical energy stores. The size of the battery determines the amount of electrolyte that can be accomodated and that determines the amount of energy that can be stored. The battery can ...
Transistor's user avatar
  • 175k
35 votes
Accepted

Why can I use P = I²R but not P=V²/R when calculating energy lost in a circuit?

60A through a 0.01ohm resistance gives a 600mV drop. That is the voltage you need to use in the equation.
Ignacio Vazquez-Abrams's user avatar
35 votes

Batteries. Why use 9V?

My multimeter uses a 9V battery and maybe draws about 10mA to function. It is very accurate. If it is powered by a 3V battery, the average current will be 40mA with a 75% efficiency. However the ...
Jason Han's user avatar
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