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Help me understand electrical math!
Posted by: Buzz
Date: August 04, 2020 08:54PM
Set of three old 3200mAH phone batteries that test out between 66% and 71% remaining health can be recharged ~5X by alleged 26800mAH new power bank. Li 3.7V vs. USB 5V is factor of 1.35. So go low (since 71% batt doesn't quite squeeze fifth recharge)....

3200 X .66 = 2112 X 5 = 10560 X 1.35 = 14260mAH

New 4380mAH with 100% health can be recharged ~3X by same power bank, so....

4380 X 3 = 13140 X 1.35 = 17760mAH

which is getting closer to alleged 26800mAH rating of power bank, which is clearly overrated.
Still >20% difference between power bank output to same phone w/ different batteries....

So, how does battery health, or lack thereof, account for this difference of efficiency?

I'm gonna go with, that the power bank should be rated at 20000mAH, since it's actually slightly smaller than our other 20000mAH power banks. New power bank is Li polymer vs. Li Ion for the older ones. I know polymer is smaller, and lighter, so I'm still trying to discern by how much. Got a 30000mAH polymer that's bigger, and heavier to start testing for accuracy, but why doesn't this electrical stuff add up? Literally?
Thanks.
==
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Re: Help me understand electrical math!
Posted by: Racer X
Date: August 04, 2020 09:11PM
loss due to waste heat as the brick discharges and the phone charges. Gotta figure that in too. Entropy is a bitch.



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Re: Help me understand electrical math!
Posted by: Filliam H. Muffman
Date: August 04, 2020 09:18PM
Percentage charge is a little bit voodoo. When it was new, my phone battery used to sit at 100% for 20 minutes of use and then start dropping.

You would need to put an ammeter in the loop to get a really good idea on what is going on.



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Re: Help me understand electrical math!
Posted by: Buzz
Date: August 04, 2020 09:23PM
Entropy is a bitch.

You want @#$%&? I'll give you @#$%&!

....oops, wrong movie.

So, an additional 20% loss between old and new batteries?
That does not compute, ...does it?

It's gonna be interesting to test the 30KmAH power bank to see how it fares....

...and it feels like a real brick!
==
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Re: Help me understand electrical math!
Posted by: Racer X
Date: August 04, 2020 09:26PM
At some point you are toting around a lawn mower battery.



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The police have no duty to respond. See Castle Rock v. Gonzales, 545 U.S. 748 (2005) or Warren v. District of Columbia[1] (444 A.2d. 1, D.C. Ct. of Ap. 1981)
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Re: Help me understand electrical math!
Posted by: space-time
Date: August 04, 2020 09:29PM
The lithium ion batteries are rated at 3.7V and your USB gizmo measures mAh at 5V. There is a loss of energy when converting from 3.7V up to 5V for USB and back to 3.7 inside the phone.

You are overthinking this. Have been posting about it for months. Just let it go. Life is short. Don’t waste it.
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Re: Help me understand electrical math!
Posted by: August West
Date: August 04, 2020 09:52PM
smiley-laughing001



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Re: Help me understand electrical math!
Posted by: Racer X
Date: August 04, 2020 09:57PM
You have wasted more energy than that power brick ever will.



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Re: Help me understand electrical math!
Posted by: RAMd®d
Date: August 04, 2020 10:31PM
You have wasted more energy than that power brick ever will.


POMTL!




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Re: Help me understand electrical math!
Posted by: GGD
Date: August 04, 2020 10:56PM
Quote
Filliam H. Muffman
When it was new, my phone battery used to sit at 100% for 20 minutes of use and then start dropping.

I could drive rental cars for 50 miles and still return them "Full"
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Re: Help me understand electrical math!
Posted by: Buzz
Date: August 04, 2020 11:09PM
You have wasted more energy than that power brick ever will.

Just trying to find the most efficient power bank, per ounce. You're right about the 30KmAH... it might be a lawnmower battery;
it's efficiency is measured by the pound, not ounce.
Trying to find a winner not to exceed ~15 - 16 oz.
==
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Re: Help me understand electrical math!
Posted by: Racer X
Date: August 05, 2020 05:11AM
facepalm

Here is something I learned decades ago. Is it really worth the time effort and money trying to chase down an extra 2 horsepower? Can you even measure that on a dynomometer? Will it even make a difference?



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Re: Help me understand electrical math!
Posted by: Buzz
Date: August 05, 2020 05:55AM
If it were only 2 horsepower, I'd be in total agreement. The performance difference between power banks is staggering, both in input and output technologies and usable speed. Plus, it seems apparent that many of the manufacturers over-represent the capabilities of their products both in capacity, and compatibility of technology. The real world differences between the product described, and the product received can also be staggering; so I've just been trying to cut thru all the bovine poop.

I've seen, per prior posts, the 26.8KmAH power bank show a 20% difference between batteries in the same phone. Dopey me was kinda excited when I got 5+ full charges from what I what a 3200mAH battery. When I found out/realized it was more like a 2100mAH battery, that excitement waned. But before that excitement waned, it was enhanced by the fast times it took to get recharged to 100%, to what I thought was close 26.8K.

It was advertised as having the latest and greatest fast charging technologies inside. I'm still fairly happy w/ its overall performance, but saddened that its real world embodiment is only about 70% of what was represented, after taking entropy into full account. It weighs a hair under 15 oz. The 30K "brick" weighs over 11 oz. more, so whatever its real world performance turns out to be, it's too heavy for some applications.

It turns out I'm willing to trade some amount of realized capacity for faster input/output performance. As noted before, ~16 oz. seems to be the comfort zone for weight. So, I'm looking for the best/most compatible I/O tech, w/ the most realized capacity at around ~16 oz., and unfortunately you can't tell jack about real performance based on anybody's written descriptions of their products.
==
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Re: Help me understand electrical math!
Posted by: WHiiP
Date: August 05, 2020 06:29AM
Somewhere, there is another forum for this specific technology. Google is your friend sometimes.



Bill
Flagler Beach, FL 32136

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Fermentation may have been a greater discovery than fire.
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Re: Help me understand electrical math!
Posted by: Racer X
Date: August 05, 2020 06:35AM
When it comes to China, batteries and specs, you can't really believe what you are told is true. Just look a 18650 batteries on eBay. Some have capacities listed as 3-30 times more than is currently possible with today's tech and knowledge. Surprisingly, one can't power a flashlight continuously, for 8 months. Who would have thought THAT? RollingEyesSmiley5

Best bet, Anker or RavPower and get one size bigger than you think is good.

I have an 18,000 from monoprice at a VERY good price, but rough guess is 15,000ish



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The police have no duty to respond. See Castle Rock v. Gonzales, 545 U.S. 748 (2005) or Warren v. District of Columbia[1] (444 A.2d. 1, D.C. Ct. of Ap. 1981)
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Re: Help me understand electrical math!
Posted by: mikebw
Date: August 05, 2020 09:11AM
I haven't really been tracking this issue, but I get twitchy when I see KmA... why not just put A?
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