Electricity and batteries

MissBlossom

youdontknowme
Does that mean watt-hours can only be compared when the volts are the same?

youdontknowme

MissBlossom In terms of real-world applications, the opposite. Watt-hours always work, but amp-hours become less meaningful the wilder the voltage swings get. The math for charging/discharging is easier with amp-hours though, if you accept a few simplifications.

Ines

I do not know how a thread about frustration ends as an physics bachelor! 😂😂

youdontknowme

Ines

Owl

Ines

I kindly suggest splitting all messages from the "Frustration-"Thread since https://unwedchastity.org/d/907-frustration/127 incl. the one at hand to a separate "Batteries and Charging"-Thread.

Besides, regarding fast charging and in addition to Tjc's correct remarks ...

Tjc At 5 volts. Traditional USB is 5 volts. Some of the newer USB-C power supplies allow the device (like a phone or tablet or iPad) to negotiate a higher voltage and higher amperage to allow faster charging. These devices are marked PD (Power Delivery)

... I just want to say, that besides USB Power Delivery there have been further proprietary fast charging techniques - like Qualcomm Quickcharge, Samsung [...] Fast Charging, ... etc. I presume most predate USB-PD, yet some seem to have gotten additional revisions after USB-PD arrived. Generally, if you don't know by heart, you have to look up and check involved devices' specs (incl cables!) to find out which "standards" they are compatible with.

For more details: See a (heavily ad-ridden but relatively comprehensive) overview here: https://www.digitaltrends.com/mobile/how-does-fast-charging-work/

MissBlossom

youdontknowme Watt-hours always work, but amp-hours become less meaningful the wilder the voltage swings get.

If I'm comparing a 5 volt battery pack phone charger to a 12 volt car jumper that has a 5 volt USB output, and they both list milliamp-hours, is there any way for me to figure out which one holds more power?

I'm sorry I'm so far off topic, but this is something I'd like to be able to figure out.

George

youdontknowme
Don't know what your problem is.

"John" solved her car problem, as she mentioned that her husband was at the moment busy and not available.

Very problem solving oriented. 😆

youdontknowme

MissBlossom The car jumper pack surprises me. You would have to figure out where the milliamp-hours are measured on both devices, then multiply that figure with the nominal voltage of each device.

LockedChasity4u

MissBlossom
The 5 volt charger that plugs into a 110 AC outlet plug- in . Will always have more Juice behind it than on that plugs in basically to a car battery. Why you ask ??? Because car batteries can be run down if it's being used for other things or electrical loads drawn as well. Where a charger being powered and supplied by a charger plug into the wall will not ever be run down .

MissBlossom

youdontknowme
So if I want to compare this (12 volts, 12,000 mAh):
https://www.amazon.com/YABER-Starter-12000mAh-Portable-Flashlight/dp/B09LH5SL12/

And this (5 volts, 20,000 mAh):
https://www.amazon.com/Anker-PowerCore-Technology-High-Capacity-Compatible/dp/B07S829LBX/

I multiply 12 x 12,000 and 5 x 20,000?

144,000 vs 100,000?

Does that mean the first one holds more, even though the second one has more mAh?

youdontknowme

MissBlossom No, it seems the capacity is given specifically for the power bank function, which runs at 5V. Also, it seems that the mAh rating of a power bank is given more as a single-cell LiPo equivalent, so it might be right to multiply by 3.6 V on both, not 5 V. But yeah, between power banks you should be able to compare mAh directly, since both single LiPo cells (the typical phone battery) and USB run at a predictable voltage.

curious

MissBlossom
Voltage has nothing to do with the energy content of a battery. You need a given voltage to drive something, so you best look at voltage as a separate factor that just has to match between battery and device you want to power.
Energy content is measured in Ampere hours.
Ampere is the current (imagine the flowing water). If your current is stronger, the content of a given bucket of water will flow over less time until it is empty. And vice versa, reduce current to a trickle and it will flow for a very long time.

MissBlossom

youdontknowme
Well dang.

For a moment I thought I understood, but that's okay. Thanks for trying! lol

Tjc

MissBlossom The Yaber can deliver 2 amps (2000 mA) for 6 hours straight, theoretically. The Anker can deliver 2 amps for 10 hours. If it takes 2 hours to charge your phone from completely from dead, the Yaber can charge it 3 times before it needs to charged itself. The Anker can do 5 charges.
I have the Anker or a model like it and am pleased with it. It is about the same size as a phone so I can carry the both in a shirt pocket (it's a tight fit) while charging. The Yaber is too big for that.

MissBlossom

Tjc The Yaber can deliver 2 amps (2000 mA) for 6 hours straight, theoretically.

At 3.6 volts, 5 volts, 12 volts, or the same at any of them?

Tjc

MissBlossom At 3.6 volts, 5 volts, 12 volts, or the same at any of them?

At 5 volts. Traditional USB is 5 volts. Some of the newer USB-C power supplies allow the device (like a phone or tablet or iPad) to negotiate a higher voltage and higher amperage to allow faster charging. These devices are marked PD (Power Delivery)

curious

MissBlossom

I wil try to use an equivalent so you can. visualise electric units more easily.

Ampere is the unit of current. Imagine flowing water instead of electricity. and this would be how much water is flowing.
Volt is the unit of the electric potential. So as water flows downhill, you can imagine this to be the difference in altitude.
If you let water flow downhill, it has an amount of energy which depends on the strength of the flow (current) and the difference in altitude. Hence it can drive for example a turbine.
Ampere X Voltage = Watt = Joule X Second

curious

Sara

Sorry, but may I suggest you read up on electricity in your physics book? I am actually correct.

Watt is the unit of electric 'work" and is defined as Energy (in Joule) per second.
So a light bulb of 60 Watts consumes 60 Joule of Energy per second.
Joule is defined as Volt X Ampere X Second.
Battery capacity is typically given in Ampere (current it can deliver) hours. Meaning it tells you what current can be delivered over a defined time.

MissBlossom

I've been reading Wikipedia (always dangerous) and I've found some contradictions.

curious Watt is the unit of electric 'work" and is defined as Energy (in Joule) per second.

According to Wikipedia, work is measured in Joules, not Joules per second, and Watt is the unit of power, not work.

https://en.m.wikipedia.org/wiki/Work_(physics)
https://en.m.wikipedia.org/wiki/Watt

curious Ampere X Voltage = Watt = Joule X Second

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

https://en.m.wikipedia.org/wiki/Power_(physics)

curious Voltage has nothing to do with the energy content of a battery.

curious Energy content is measured in Ampere hours.

According to Wikipedia, Kilowatt-hours is a measurement of energy and amp-hours is a measurement of charge.

https://en.m.wikipedia.org/wiki/Kilowatt-hour
https://en.m.wikipedia.org/wiki/Ampere-hour

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."

I'm not sure who's right between @Tjc, @youdontknowme, @WriterAlexis, and @George, but I'm pretty sure it's not @curious.

George

Owl It's even more complcated. Quickcharge 4 is a rebadged PD.

(Happens all the time: Thunderbold 4 is actually USB4 with a number of optional features ticked as non-optional. Thunderbold 3 OTOH was a completely different beast, as "extend your PCIe bus over a cable" thing. Which is if I remember correctly, interestingly an optional feature of TB4 ports for backward compatibility)

George

WriterAlexis No, energy is what counts in the end. Actually from an engineering point of view energy that the battery can provide in an acceptable voltage/current range.

OTOH, for specific batteries (e.g. for cell phones), the voltage is usually well understood, so you can get away with specifying the current.

For DC, UIt gives you energy. And for AC it gets way more complicated, which might be also a reason why EV batteries that are capable to be charged via built in AC chargers are specified via Wh which nicely hides all that complexity without being wrong.

Angelina

WriterAlexis If you get hurt on a scooter, you were probably doing something dumb. Like riding an electric scooter.

best comment and 100% agreement 😂 👍️

But please, this no longer has anything to do with frustration, even if my frustration about the ban on combustion cars is very strong

MissBlossom

Angelina But please, this no longer has anything to do with frustration

I'm frustrated with the contradictory answers in this thread! lol

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