Electricity and batteries

WriterAlexis

My sister's LOVENSE Lush 3 comes with a Li-Ion Rechargeable battery

My new order of places I don't want a battery fire-

Something 'twixt my nethers.
Vehicle I am riding in.
Phone in pocketbook/clutch.

youdontknowme

Work/energy is total output over an extended period of time. Power is instantaneous output, but they are closely related. Basically, you could say that power is how hard it works, time is how long it works. In the end, how much it works depends on both.

MissBlossom And since Watt-hours = Watts x hours = volts x amps x hours, I don't see how it's possible that "Voltage has nothing to do with the energy content of a battery."

Most batteries stay at a relatively stable voltage over most of their useful life, so while measuring the voltage can tell you how full a battery is, there is a very indirect relation between the voltage of the battery and how much juice there still is in it. If it goes significantly below the nominal 3.6 V, it is empty, if it is much higher than that, it is full to the brim, but outside of those extremes it will stay at around 3.6 V for a loooong time.

Voltage absolutely has an effect on how much work you can do (per time) with a given amount of amps (which is why those big transmission lines that go between cities run at hundreds of thousands of volts), But when you compare similar batteries, the voltage is practically the same between both, so using Amp-hours is enough for comparing their juice.

MissBlossom

youdontknowme
I was talking about the energy of a fully charged battery.

Am I right in thinking that a 12 volt battery (not a device with a battery with less volts that somehow puts out 12 volts, but an actual 12 volt battery) with 1,000 mAh holds more energy than a 1.5 volt battery with 1,000 mAh?

youdontknowme

MissBlossom Yes.

To give some more context, some usual designs of 12 V battery include lead-acid batteries, which have about 6 cells of 2 volts each in series. Each cell has a given amount of energy, and obviously six cells have about six times as much energy as one cell has, but the mAh of the battery is the same as the mAh of each one cell.

MissBlossom

youdontknowme MissBlossom Yes.

Oh good, I finally get it.

youdontknowme To give some more context, some usual designs of 12 V battery include lead-acid batteries, which have about 6 cells of 2 volts each in series. Each cell has a given amount of energy, and obviously six cells have about six times as much energy as one cell has, but the mAh of the battery is the same as the mAh of each one cell.

WHAT??

I guess I don't. lol

youdontknowme

When you wire two batteries in series, you get more volts, but the amps stay the same. When you wire two batteries in parallel, you get the same volts, but more amps. Either way, the energy / power adds up.

MissBlossom

youdontknowme
Thank you for trying to explain, but I think I now know what I wanted to know, and I don't plan to make my own batteries. lol

Between power packs, I can just compare mAh.

With power packs, I multiply by 3.6 to get mWh.

With real batteries, I multiply by the volts to get mWh.

With batteries that have different volts, I compare mWh (for example, comparing a power pack to a real 12 volt battery).

Right?

If so, I'm done here.

Tjc

Voltage is the amount of "push" that a battery has. A 12 volt battery has more push than a 5 volt one. Amperage or Amps is the amount or rate of flow in an electrical circuit. A milliamp (mA) is one thousandth of an amp.
A milliamp-hour (mAh) is one thousandth of an amp flowing for 1 hour.
A 500 mAh battery could supply 1 mA for 500 hours or 500 mA for 1 hour. (This is theoretical)
If it is a 5 volt battery it would have 5 volts of "push" for the 500 hours or for the 1 hour.
If it is a 12 volt battery, it would have more push so it could run a bigger motor or run a motor faster than the 5 volt battery.

All batteries are made from one or more cells. The amount of voltage of the battery depends on the number of cells and the chemistry of the individual cell. Different types of cell chemistry produce different voltages. (1.1, 1.2, 1.5, 2.0, 3.6). Depending on haw the cells are connected you can get more voltage or more amp hours.

MissBlossom

Tjc
Does that mean "yes" or "no"?

Tjc

MissBlossom Does that mean "yes" or "no"?

In general, if you are powering things with USB, the more mAh, the better.
What actual problem are you trying to solve? What is you application?

curious

MissBlossom According to Wikipedia, "the unit of power is the watt (W), which is equal to one joule per second" not Joules x Seconds.

That's correct. Was a mistake on my side. Should not do physics too early in the morning.

MissBlossom

Tjc What actual problem are you trying to solve? What is you application?

I just want to know how to compare batteries and power packs.

You could say I want to be able to figure out which one's bigger without opening the package and testing it out.

If my summary above is correct, my problem is solved.

Tjc

MissBlossom If you are comparing USB batteries and power packs for phone and tablets and things like that (Not starting cars) the more mAh, the better.
If you are comparing a 12 volt battery and it has USB output, it will turn the 12 volts into 5 volts internally so you don't need to take the 12 volts into account.
The rest of what you said is correct

WriterAlexis

Tjc

If you are comparing USB batteries and power packs for phone and tablets and things like that (Not starting cars) the more mAh, the better.

Bingo was his name-o.

MissBlossom

Tjc youdontknowme
Thank you.

youdontknowme

Unless you are completely repurposing electronic components (in which case you should better know what you are dealing with instead of relying on internet strangers), any product that advertises USB output is going to provide capacity either in Wh or in a mAh figure that works like that of power banks. Else they would be shooting themself in the foot by underreporting their capacity compared to the competition.

cilarith

youdontknowme any product that advertises USB output is going to provide capacity either in Wh or in a mAh figure that works like that of power banks. Else they would be shooting themself in the foot by underreporting their capacity compared to the competition.

Except when they either intentionally lie or print misleading bullshit because they don't know any better (both situations being unfortunately common). When it comes to characteristics that cannot be easily and independently measured by the end user, anything which does not come from a known, reputable supplier (and is known not to be a forgery) is suspect. And batteries are in exactly the middle of the venne diagram of "extremely common", "surprisingly hard to accurately measure", "sold purely by advertised specifications" that make them ripe for such abuse.

I've come across a few power banks which made clearly impossible claims - e.g. a 2-cell pack, containing 2 18650 cells, claiming both a voltage and charge capacity that would require a minimum of 4 cells (7.2v, 5500mAh). Whether that an intentional lie, or simply incompetence at calculating basic specifications, is unknowable.

Joh

MissBlossom I agree with @Tjc . If you want to compare it look at the different devices as a black Box. What realy matter is the voltage at the Connection Point and current hours it can Delivery. What realy Happen inside is Not relevant for your comparison

youdontknowme

cilarith Sounds consistent with what the TP-Link document says. 2 Lithium-ion cells in series would add up to 7.2 V, and they could contain as much energy as a 5500 mAh LiPo cell.

Of course it is rather disingenuous to advertise both in the same figure, since when they are wired in series like that you are going to have the two (I assume) 2750 mAh cells discharged with half as much current draw. But the industry convention appears to be to just add up the charge of each cell, since that is how much phone battery it could top up if you completely ignored inefficiencies. Plus when comparing two power banks, you do not care about the voltages they use internally, you care about what you can get out of the battery at the end of the day, and marketing it as a 2750 mAh power bank would be underselling it compared to a 3.6 V 3000 mAh power bank.

Really, they should have just standardized on something more sensible, like Wh or mAh at 5 V, not mAh at 3.6 V. The simple "can top up your phone battery N times" metric does not work anyway because efficiency has not been factored into the mAh figure to begin with.

WriterAlexis

cilarith

Except when they either intentionally lie or print misleading bullshit

Within a capitalist model, that's a feature, not a bug.

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