expired Posted by DesertGardener | Staff • Apr 13, 2023
Apr 13, 2023 3:10 PM
Item 1 of 5
Item 1 of 5
expired Posted by DesertGardener | Staff • Apr 13, 2023
Apr 13, 2023 3:10 PM
WEWATCH 20,000mAh 65W USB-C PD Portable Charger Power Bank
+ Free Shipping$20
$70
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As per the Amazon review picture, the capacity is 20000 mah @ 3.6v and the rated capacity is 11000 mah @ 5v. The difference in voltage causes a difference in mah and the rated capacity usually takes in the loss conversion (usually 25% loss is calculated as stated by Anker).
The equation from stated capacity to rated is: 3.7v x Advertised capacity x efficiency / 5v. Plugging in the numbers: 3.7 x 20000 x 0.75 / 5 = 11,100 mah @ 5v which is what is stated on the power bank.
So TLDR: 11000mah @ 5v is the same as 20000 @ 3.7v with conversion loss and powerbanks should just use Wh as to measure capacity instead of mah to avoid this confusion.
3.6V*20Ah = 72Wh.
5V*11Ah = 55Wh.
That is 17Wh of loss converting or 55/72 = 76.4% efficiency
This efficiency is usually expected because this design is probably boosting and then bucking to get the continuous 5V. A better design is to just boost, but it gets tricker to regulate the voltage constantly at 5V. And the design is probably more complicated to just do boost without bucking.
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does it has passthrough?
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does it has passthrough?
From the Amazon reviews, the print on the charger and manual show 20,000mah.
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From the Amazon reviews, the print on the charger and manual show 20,000mah.
Ah, I see now. Thanks for mentioning!
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I guess $20 is still fine for what you get, but what you get is some really cheap components.
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As per the Amazon review picture, the capacity is 20000 mah @ 3.6v and the rated capacity is 11000 mah @ 5v. The difference in voltage causes a difference in mah and the rated capacity usually takes in the loss conversion (usually 25% loss is calculated as stated by Anker).
The equation from stated capacity to rated is: 3.7v x Advertised capacity x efficiency / 5v. Plugging in the numbers: 3.7 x 20000 x 0.75 / 5 = 11,100 mah @ 5v which is what is stated on the power bank.
So TLDR: 11000mah @ 5v is the same as 20000 @ 3.7v with conversion loss and powerbanks should just use Wh as to measure capacity instead of mah to avoid this confusion.
Our community has rated this post as helpful. If you agree, why not thank LeviathanUltima
3.6V*20Ah = 72Wh.
5V*11Ah = 55Wh.
That is 17Wh of loss converting or 55/72 = 76.4% efficiency
This efficiency is usually expected because this design is probably boosting and then bucking to get the continuous 5V. A better design is to just boost, but it gets tricker to regulate the voltage constantly at 5V. And the design is probably more complicated to just do boost without bucking.
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i am looking for a smaller battery for my steam deck and this would fit the bill (hopefully)