# Tag Info

32

It's marketing, like PMPO watts. Big numbers sell! If the battery is 1.2V nominal, there won't be a big difference between W.h and A.h numbers. But if the battery is 3.6V nominal, the W.h number will be 3.6 times more bigger than the A.h number! So a 1200 mWh 3.6V battery sounds a lot better than a 330 mAh battery... even though it's the same battery of ...

18

cIt's complex, and some of the answers are "soft" and some of you assumptions are (reasonably enough) inexact. Li-ion are measured in mWh LiIon cells are frequently measured in mAh capacity. LiIon batteries (1 or more cells) often have mWh and mAh markings. Neither is a certain measure of what a user will receive. Both are useful. (cf George Box's "All ...

8

That's a 27A-size battery, not a battery capable of providing 27 amperes of current. The maximum current from that battery can best be described as "piddly", which is all a remote control needs.

7

Not all loads are constant power or constant resistance or constant current or constant in any other category as the voltage drops at 20% and the double layer effects in all batteries as well as the double C (Farads) and ESR (milliohms) products affect the high drain capacity reductions more. Squeezing out the last 10% SoC might result in 30% drop in ...

6

Like most batteries, Alkaline batteries produce electricity through chemical reaction. This produces byproducts like liquid and gas. The former can be seen when a battery goes bad and leaks out. The latter can be heard. It's normal for hydrogen gas to be produced. The batteries are not sealed, to allow this gas to vent. But misuse of the battery, or if it ...

5

Alkaline battery capacity depends too much on load, it's too complex for the average consumer to understand and the difference between brands is small. Primary (non-rechargeable) lithium AA cells have more stable capacity but they are oriented to the same market. Capacity for NIMH batteries actually is quite stable under load. There is a trade-off between ...

4

The power supplied by a DC->AC converter to its load comes from the DC input. The part you've chosen, an LPS09-3-5, is designed for driving an EL panel, rated at 5 unit loads. In this case, a unit load is defined as 20nF//100kohm, taking 6.1mA at 120v rms at 400Hz. The specification goes on to say that each unit load requires 500mW of input power from the ...

3

Traditionally, battery capacity was specified in mAh or Ah. When the only rechargeable types commonly used were Nicad, NiMH and Lead-acid, it wasn't hard to relate to because only two voltages were involved - 1.2V for Nicad/NimH and 2.0V for lead-acid. But then Li-ion cells became available with various nominal voltages, which made relating their energy ...

3

Where can one find the standard specification for regular alkaline AAA, AA, C and D batteries? The international standard is IEC 60086, specifically: IEC 60086-2:2015 - Primary batteries - Part 2: Physical and electrical specifications (current cost is CHF 250) Abstract: IEC 60086-2:2015 is applicable to primary batteries based on standardized ...

3

Typical Alkaline AA is 2000-2300mAh. Self discharge is around 2-3% per year or 60mAh. I've tested 100 mA discharge rate to 1.1V, yielding around 1800mAh. For so much lower than this, I would expect you get very close to nominal capacity. This would be around 800 hours. This is assuming your mean load doesn't include high spikes. Alkaline internal ...

3

Originally, all microcontrollers were designed to work off of 5v. Then 3.3v logic was introduced, and microcontrollers came out running off of that voltage. Since then, those have been the two standard voltages, with 3.3v becoming the most popular. Although many microcontrollers can go down to 2.7 or 2.6v or even lower, IMO it is best to run them off of 3....

3

I guess you shown us a lithium because you failed to find the equivalent photo with an alkaline battery. Actually, I doubt you can find pre-made alkaline batteries with the terminals as shown. So if your concern is manufacturability, that's something to check first. Moreover, in case your circuit is mainly SMT with only the alkaline battery being through ...

3

Don't use any sort of rechargeable cells. They will be flat through self-discharge by the time you use them. Non-rechargeable lithium cells aren't common in the size you want, but if you can source some, then they will last many years. Otherwise, get brand new alkaline cells from a reputable manufacturer. Check the "install by" date on the ...

2

Even an amp for a few milliseconds isn't going to harm them at all and a mA for a few seconds isn't going to much either, you'd need to be pushing several watts for quite some time before you would experience any real problems (you can always swap out the alkalines for rechargeables if you are still worried, there are NiZn cells that have the same voltage as ...

2

Battery capacities are usually specified in milliampere-hours, or mAh. You don't say what the capacity of your batteries are, but you can usually find it in the manufacturer's datasheet. You also need to know the current draw of the LEDs. For a typical LED, such as the one in your picture, it's about 15mAh typically. This is probably reasonable for a cheap ...

2

If the lowest testing current you found was forty times higher than your load, take the time from the curve and multiply it by forty, you'll have the time you can stand with your load. Actually, it will certainly be significantly more than that, because, at lower current, the internal resistance of the battery has less effect. So you'll gain more mAh. Here ...

2

It doesn't matter what is the voltage on LEDs, 2.77 V is about right for modern LEDs. However, three alkaline batteries should be delivering at least 3.3 v to 4.5 V under this modest load, so there must be some other circuit (or just a resistor) in series with this bunch of LEDs. However, nothing of this matters, the only 76 mA is important. Your estimation ...

2

Some switches themselves are to blame. Many cheap slide switches are simply two metal plates that slide over each other. Sometimes one is shaped with a curve to add a bit of spring action. This type of switch is rife with friction, and sometimes there is dirt build-up and such. The device may turn "off" (a motor stops spinning) but there can actually still ...

2

Batteries installed in devices are almost certainly partially discharged. Nobody puts fresh batteries in a device and doesn't immediately use it, at least a little bit. Any discharge at all produces hydrogen gas, which raises the internal pressure of the cell. This can only accelerate any leakage.

2

Each manufacturer of a battery chemistry category will try and evaluate the temperature behavior of their commercial technologies, because doing so may give them a new market worth pursuing. (Or let them know which markets NOT to pursue.) Some battery types don't even work until the temperature is over $60^\circ\text{C}$. While that might seem bad, it's ...

1

Lithium has much higher Coulombic efficiency than NiMH, but mWh is a more useful value as a unit of energy. Lithium are often rated for a 20% drop in voltage 3.8 to 3.0 NiMH are often rated for a 30% drop in voltage 1.3 to 0.9V but only 20% in large strings to prevent reverse V. So that is similar. Alkalines do have a very good mAh rating , it's just not ...

1

You need special $batteries and derate capacity. A lot! We used Silver Oxide [packs in the 70's to -50'C Silver Oxide types are your best bet. They actually are made in LOTS of sizes but$\$. This one is cost-effective. https://data.energizer.com/PDFs/silveroxide_appman.pdf If you can insulate and keep near earth in a protected structure and increase ...

1

Usually not, but sometimes. Most devices that run off of two AA cells or similar are just powered directly from the two cells in series. The components inside the device are chosen to be able to operate over the valid voltage range of the two cells. For example, there are many microcontrollers, especially those intended for low power applications, that ...

1

Batteries are complicated chemical reactions. The 30mAh will be when drawing some specific current. A larger or smaller draw will change that value. So will temperature. What's the maximum current you can pull? Well, the battery has an internal resistance which will limit the current. The formula is I=V/R. How long will it last at that level? No idea, but ...

1

An AA alkaline battery's voltage starts at 1.5 and drops to 0.8V cutoff. This makes alkaline a poor choice for powering an LED. You want a flatter discharge curve. Li-ion is a much better choice. You could easily power these LEDs with a single 18650 battery. The lifespan is determined by the discharge rate. At 25mA expect 3000 mAH. At 100 mA expect ...

1

Boost converters are rated by input current, so a 600mA boost converter can't make 600mA at 5V with a 3V input With alkaline cells you should design for 1V per cell unless you want to waste money replacing the AAs when they still have 80% charge, For 600mA at 5V from 2xAA input you should use boost converter rated at more than 1.5A. eg: XL6009.

1

It would (for all intents and purposes - there is always some leakage). However, a more significant issue is the fact that it will also drop almost half of you AA battery voltage - and thus waste half of the energy inside the battery. There are two options to mitigate this: Battery protection circuits with some form of switch, such as a mosfet: These exist ...

1

Energy capacity of a AA alkaline cell is about 2000 - 2500 mAh. So it will last maybe half an hour. From your experiment, about 50% of power is dissipated on internal resistance of the cell, internally. This power will be about 1.5- 2W. The alkaline battery cell will become pretty hot, but it won't burst into flames or explode. So you should be safe.

1

You can test V with a 1A analog current meter for a blinking fraction of a second and bin them, as this will allow you to measure (almost) short circuit current and thus capacity. Combine say 10 bins into fewer bins as needed to optimize matching. Mismatched cells are useless as the series capacity and ESR is controlled by the weakest cell. Car batteries ...

1

In my experience, AA batteries fairly well never have a capacity >2.7Ah (usually 1.8-2.3Ah), so as long as your pack of series-connected AAs lasts >1hr in use, then you're for sure safe. EDIT: At very worst, the 12V/2A power supply might yield a small reduction in initial power vs. the batteries, but should for most purposes be sufficient.

Only top voted, non community-wiki answers of a minimum length are eligible