Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [capacity]

131 questions
64
votes
1 answer

Duracell PowerCheck - How Does It Work?

I've been using these batteries for a long time and I've never seen such a feature. There's a band on its outer wrapping having two ends: The white circle on the left side and the another one on the right side (not visible because it's under my…
Rohat Kılıç
  • 26,954
  • 3
  • 25
  • 67
17
votes
5 answers

Wouldn't charging a lithium battery to 80% only defeat the purpose of putting the battery into longer use in the first place?

I see most smart devices (laptops/tablets/phones) now have the option to optimize your battery by charging it to 80% only. But wouldn't this reduce your capacity i.e. your brand new battery now only has 80% of its rated capacity, which means more…
GuitlyofNtAsking
  • 191
  • 1
  • 6
15
votes
5 answers

Are varicaps (capacity diodes) obsolete?

I have read that varicaps (capacity diodes) are a "modern" alternative to variable capacitors. In several electronics books only positive properties of varicaps are mentioned. But several major distributors (here in Germany) simply don't offer…
java.is.for.desktop
  • 301
  • 2
  • 6
12
votes
2 answers

Why is channel capacity a factor of bandwidth instead of frequency?

I'm trying to understand the concept of capacity for a wireless channel. Some help would be appreciated. For a AWGN channel capacity is calculated as: $$C=B \cdot log_2(1 + S/N)\text{ bits/sec}$$ B = bandwidth. This is what I don't understand. …
Drew
  • 123
  • 1
  • 4
11
votes
1 answer

Current carrying capacity of 28 AWG wire?

This SCSI cable is composed of 28 AWG twisted pairs. According to an L-Com "tip", such a twisted pair should be able to carry at least \$3 \times 0.8=2.4\text{ A}\$ per conductor. However, this other web site which references the Handbook of…
ajs410
  • 8,381
  • 5
  • 35
  • 42
11
votes
5 answers

What is the valid capacity ranges of Lithium Ion 18650 batteries?

I'm seeing wildly varying capacities that are seemingly fake on 18650 cells, such as these "9,800 mAh" ones on eBay, but are ~$1 / cell. However, 'genuine' cells from Panasonic and similar name brands seem to top out around 3,500 mAh or so, but cost…
Ehryk
  • 1,141
  • 5
  • 16
  • 28
10
votes
2 answers

Properly charging and discharging Lithium cells during battery testing?

I'm working on some software that automates charging and discharging battery cells to generate discharge curves. I have a few concerns about properly charging and discharging of lithium-ion / lithium-polymer cells: Concerns: I understand when…
Rob
  • 291
  • 1
  • 11
9
votes
3 answers

Is 18650 battery capacity from 3V or 0V?

To calculate the battery capacity in mAh of an 18650 battery I understand you can use something like an iMax B6 in discharge mode on a fully charged (4.2V) battery to get the mAh it provides. The iMax B6 stops at 3V. So my understanding of this is…
GazB
  • 193
  • 2
  • 5
9
votes
4 answers

Is my phone battery better / more capacitative than my laptop battery?

When we go out and look for phones, the first thing I do I always look at the battery capacity, usually 2000 mAh, 3000, up to 10000 mAh for a (external?) battery. Looking at laptop batteries, they are much much larger and have only afraction of…
Gizmo
  • 381
  • 1
  • 3
  • 12
8
votes
7 answers

How do I find the maximum "discharge C rating" of a battery?

I've been experimenting running my 3A LED strips off battery power and the results are disappointing. I'm only getting a few minutes (< 10) out of a YSD-168 1800mAh lithium ion. How can I find the "C rating" of this battery? Is it something mainly…
Robert Atkins
  • 2,155
  • 3
  • 23
  • 37
6
votes
2 answers

UPS vs portable power station capacity ratings

I have been looking to buy a dedicated 220V AC offline UPS or portable power station with an offline UPS functionality. What surprised me is that, whereas both are very similar devices, is that portable power stations are often rightfully so…
JJM Driessen
  • 179
  • 5
6
votes
1 answer

What is the capacity of capacitors in this power supply circuit?

Imagine the following circuit with two capacitors and diodes acting as passive PFC. My question is what is the capacity of these two capacitors? I mean compared to a circuit with just a single capacitor. Some people say they are in series so their…
Al Kepp
  • 2,971
  • 7
  • 26
  • 32
5
votes
1 answer

Issues ascertaining current x time for battery life

It is simple to calculate a continuously-on device's theoretical battery life based on the battery datasheet capacity (assuming always nominal voltage, etc.) An LED @ 20mA.. 2800mAh / 20mA = 240 hours. The issue I am having is verifying calculation…
Tom Paris
  • 272
  • 1
  • 3
  • 9
4
votes
3 answers

Why battery specs are given in contextless mA·h instead of meaningful W·h?

Possible Duplicate: Why are deep cycle batteries rated in amp hours instead of watts hours? I don't understand why it is so common for specifications of battery capacity to be given in mA·h, when you have no clue how much power that is and how…
cnst
  • 227
  • 3
  • 9
4
votes
7 answers

Excess capacity in the power grid

My question concerns capacity in the power grid. I am an attorney trying to understand whether excess capacity runs in a power grid to avoid brown outs and how long can the excess capacity exist within the grid before it is dissapated or used? …
Lawbit
  • 51
  • 8
1
2 3
…
8 9