46 votes
Accepted

Does it matter if a fuse is connected to the negative or positive terminal of a battery?

[Should I] connect the fuse to the negative terminal of the battery since it's where the actual flow of electrons originate which is opposite to the conventional flow of current from the positive ...
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  • 159k
45 votes

How to solder wires on Li-ion cell phone batteries?

Don't. The battery manufacturers specifically tell you not to do this, as the batteries are quite heat-sensitive. If you manage to set one on fire, you can't extinguish it either: it reacts ...
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  • 44.9k
40 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 ...
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  • 491
33 votes
Accepted

Unknown component in an electronic dictionary

That is a piezoelectric buzzer: Photo from the linked Wikipedia article.
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  • 57.4k
30 votes

Can I disable a battery powered device by reversing half of its batteries?

If the batteries are not perfectly balanced they would still have some net voltage. And that is assuming that the batteries are connected in series. If the batteries are connected in parallel, ...
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  • 3,757
30 votes

My DIY RGB LED panel powered by 9V battery works but certain colors like blue, white, and purple don't work

It is a bit hard to see from the picture, but since each LED has six pins, and knowing that it is meant for 12V supply, it is extremely likely that the LEDs might be arranged so that there are three ...
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  • 87k
29 votes

Possible battery solutions for 1000mAh capacity and >10 year life?

First, let's see how much energy or capacity you need. 70 µA for 10 years comes out to 6.1 Ah, and you say this is at 3 V. That's a lot more than a CRxxxx battery can do. Another problem is ...
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27 votes

Would a 7805 5 V regulator drain a 9 V battery?

What could explain such a short battery life? Could it be the 5v regulator? As mentioned, the 7805 has about 4mA of quiescent current. You need to find a data sheet for the battery (Eveready has ...
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  • 35.8k
27 votes

Can I disable a battery powered device by reversing half of its batteries?

You can, but as per @Dampmaskin's answer, it's not really the best plan. Why not do as often seen in new electronic devices, and inserst a plastic slip between a battery and one of the terminals (or ...
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23 votes

Possible battery solutions for 1000mAh capacity and >10 year life?

Long lasting (very low self-discharge) batteries usually doesn't have a very good discharge characteristics. For example Tadiran SL-360, 14500 form factor offers 2.1AH at 6mA discharge but can not ...
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23 votes

Why do batteries in consumer electronics get used unevenly?

There will always be some variation in capacity between batteries. In toy use the current is typically drawn at a high level compared to many other applications, so the internal resistance of the ...
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22 votes
Accepted

Why do smoke detectors run off 9v batteries?

The sensor (typically an ionization chamber with some radioactive Americium 241) is normally specified at 9V. I think it would work at a lower voltage, but with less sensitivity. More information ...
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21 votes
Accepted

How to solder wires on Li-ion cell phone batteries?

Step one is trying to avoid wanting to solder to any kind of pre-fab battery, as you don't know 100% for sure what's in them in ways of protection. Step two is really thinking hard if you can't stick ...
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  • 18k
21 votes

How to solder wires on Li-ion cell phone batteries?

There are Li-ion batteries and battery packs designed specifically to be soldered, which usually look like this: I'd strongly suggest you buy one of these instead of trying to reuse a cell phone ...
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20 votes

Why do batteries in consumer electronics get used unevenly?

Toys are often supplied with the cheapest battery cells which may be lower capacity, but also have the widest tolerance. This tolerance and the "weakest cell's fails 1st" is the general rule. To ...
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19 votes

My DIY RGB LED panel powered by 9V battery works but certain colors like blue, white, and purple don't work

Blue LEDs require a higher voltage than red and green. If the panels are designed to work on 12 V, there may not be enough voltage to light the blue LEDs when run on 9 V. The blue LEDs must work for ...
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16 votes

Why do batteries in consumer electronics get used unevenly?

In addition to the notes on battery manufacturing tolerances, I have seen (at least one) device that would split off battery electrical connections to different parts of the circuit. In my case, it ...
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  • 865
14 votes

How to solder wires on Li-ion cell phone batteries?

Use conductive glue. Here's an example. A few caveats, taken from the reviews: It isn't tacky.. so either use a clamp, or be prepared to hold the object (for a long time.) It's thin & watery.....
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14 votes

Lithium Coin Cell CR2032 battery specifications

From the data sheet: Nominal capacity indicates duration until the voltage drops down to 2.0V when discharged at a nominal discharge current at 20 deg. C So, if you discharge at a steady 0....
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  • 70.7k
14 votes

Does it matter if a fuse is connected to the negative or positive terminal of a battery?

Since the negative terminal of the battery is normally considered "Ground" or "Zero Volts", a fuse in the negative lead would leave the rest of the circuit "hot" - usually Not a Good Thing. ...
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13 votes

Can I disable a battery powered device by reversing half of its batteries?

Very often, multiple batteries are series-connected. And the total voltage is used to power "stuff". In that case, flipping a battery to turn off current works just fine. However, the less-usual case ...
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  • 18k
13 votes

Would retro-fitting a DC motor as the blower motor in a residential furnace be more efficient than existing 1/2 hp AC motor?

Brushed DC motors do not have the longevity of induction motors. They are also not particularly efficient. You may be able to find a BLDC motor with built-in control that could run from DC and be more ...
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  • 24.2k
12 votes
Accepted

How does this mosquito zapper circuit work?

Looks like a self-oscillating converter, probably a primary winding, a feedback winding and a secondary winding (6 pins). It would be similar to this, but with many more turns on the secondary: I ...
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12 votes
Accepted

Using DC voltage instead of AC to supply SMPS

I have practical experience with PC power supplies. Pretty much any modern ATX PSU contains a main section (that delivers full horsepower when the PSU is on) and a tiny section to deliver +5VSB. In a ...
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  • 2,240
12 votes

Would a 7805 5 V regulator drain a 9 V battery?

All those parts can run from 3 to 5V so use a battery that doesn't need a regulator, a 16500 Li-ion cell, or a 3xAAA battery pack are about the same size as the 9V and produce voltages in that range. ...
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  • 26.6k
12 votes

I need to power a device that requires 12V and 0.43A, with as small of a battery as possible

You have a 430mA load and want it to last 2-3 days. That's 48 to 72 hours. Doing the math, you need a 21 to 31 amp-hour battery. That's approxmately one large motorcycle battery.
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  • 87k
11 votes
Accepted

How much current can lead acid batteries safely supply?

Lead acid batteries are fantastic at providing a lot of power for a short period of time. In the automotive world, this is referred to as Cold Cranking Amps. From GNB Systems FAQ page (found via a ...
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11 votes

Would a 7805 5 V regulator drain a 9 V battery?

The idle current of a 7805 regulator is around 4 mA so, armed with the ampere hour capacity of your battery, work out how long it will last with a continuous drain of 4 mA. If you establish that is ...
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  • 378k
11 votes

Nichrome wire not heating up with a 9v battery

A 9V battery is a poor choice for providing electrical energy for heating. An Alkaline 9V battery can typically provide maybe a few watts of heat energy for a short while. If your wire resistance is ...
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  • 142k
10 votes

Simple, efficient "breathing" LED circuit

A CR2032 has a capcity of ~ 200mAH. For 2 weeks, this gives you an average current budget of ~ 500 uA. A plain 555 has a supply current of a few mA, so you'll need to use a cmos 555, which has a ...
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