AnswerBun.com

Help me to understand VOOC fast charging for lithium ion batteries?

Electrical Engineering Asked by Ridham on December 13, 2020

I know common VOOC charger have fast charging rate of 18W(9V/2A). But how it possible even current is only 2A. I mean 2A current have only stored charge 2000mAh(2A*1h). How changing voltage can charge battery faster?
On other side Oneplus Dash charger supports upto 20W(5V/4A). This makes sense that higher current can charge battery faster. But again how can just 5V can charge battery to 4A rating?

Thnaks for answer/comment. Corrections and suggestions are welcome.

One Answer

Li-ion cell charging voltage ranges from ~3.7V to 4.2V. 18W/4.2V = 4.29A. The charger has a DC/DC voltage converter circuit which pulses current through an inductor to 'transform' the voltage down and current up. This process is typically 85~90% efficient, so it should be able to deliver 4A for most of the charge cycle.

But again how can just 5V can charge battery to 4A rating?

20W/4.2V = 4.76A, or ~4A at 85% efficiency. The OPPO VOOC (Voltage Open Loop Multi-step Constant-Current Charging) 'Flash Charging' system claims to charge certain OPPO devices from 0 to 75% in 30 minutes, implying a capacity of ~2.7Ah.

At 4A a 4Ah cell would only get 50% charge in 30 minutes. Charging to 75% would take (4Ah x 75%) / 4A = 45 minutes.

At 75% charge the cell has probably reached 4.2V, then current must be reduced to avoid damaging the battery. Getting The last 25% into the cell may take another 20-30 minutes.

Answered by Bruce Abbott on December 13, 2020

Add your own answers!

Related Questions

Reduce Noise Added With Zener Clipper

1  Asked on August 26, 2020 by oats

     

Ohms law’s statement

5  Asked on August 26, 2020 by ashaal-aalam

       

15V to 3.3V to power ESP12E

2  Asked on August 22, 2020 by muxa

   

How to attach a clincher connector to a FSR

1  Asked on August 9, 2020 by cerin

     

Understanding addressing and size in memory map

1  Asked on July 28, 2020 by kmc

     

Read 24 Vac signal with a Raspberry Pi

1  Asked on July 25, 2020 by riccardo-minati

         

Ask a Question

Get help from others!

© 2022 AnswerBun.com. All rights reserved. Sites we Love: PCI Database, MenuIva, UKBizDB, Menu Kuliner, Sharing RPP