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Why do I see random people on websites giving answers that make no sense?

zionosis

Oct 23, 2013
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I am not talking about this website here, I am talking about another one that is mainly a question and answer site. I also see lots of times the "best" chosen answer is actually flat out incorrect.


So basically guys it's about charging lithium batteries like in a laptop. The person claimed that if you charge a lithium cell at lower than the suggested charging voltage that it will still take the same time to charge as the suggested voltage, but somehow the battery will claim it's fully charged at the voltage that is commonly known as the limit. (Like 4.2v generally). He said it will really only be 50% charged but everything will report it as fully charged 0_o.

This person also claimed that if you charge the lithium battery at a voltage higher than suggested and charge it really fast, it will have a longer discharge time.



How does this even make sense? Plus I am pretty sure the way to change charge times is to change the current in which you charge the battery at, I am pretty sure that you are not meant to adjust the voltage and somehow charge a lithium battery at 6V and lets say 400mA.

Pretty sure you should charge it at the suggested voltage and just raise the current instead if you want it to charge faster.



Plus I am pretty sure that if you charge at a voltage lower than the batteries suggested full voltage. (Say you charge the lithium cell with only a 3.8v power supply) I am pretty sure that you will never be able to fully charge it at that voltage, no matter what that other person claims. You cannot connect a 3.8v PSU to a lithium cell and just wait long enough and somehow find the cell at 4.2v.



What do you guys think? This only bothers me to see these peoples claims get best answers.
 
Last edited:

Arouse1973

Adam
Dec 18, 2013
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Hello Zionosis

Lithium ion batteries need a two stage charging sequence to achieve full charge. This is constant current usually 1C but can vary between manufactures. The constant current is applied until the desired peak voltage for that cell is reached. The charger should then switch over to constant voltage charge (4.1-4.2). If you use the lower 4.1 Voltage the battery will achieve around 80-90% capacity, this is often done to prolong the life of the battery because any slight amount of over charging is very bad for lithium batteries.

Now if you were monitoring the terminal voltage of the battery and not the current then you could mistakenly terminate charging early as you would have reached say 4.1 Volts after 1 hour. But you will only have around 50-60% capacity. The finishing charge of a lithium ion battery takes approximately the same amount of time for all sizes and that's about 3 hours.

Fast charging Lithium ion batteries to achieve 100% is not possible. Fast charging will only shorten the time to the peak voltage required. The battery will still have to go through the finishing charge for say 3 hours. Some say that if you fast charge the finishing charge will take longer, I have never monitored this.

To correctly terminate the battery to achieve 80-90% charge is to monitor the current and I use 10% of the capacity. This is because if you choose too low a value the batteries may never terminate because the larger cells have a higher leakage current.

I would not recommend charging any battery outside of the manufactures specifications.

Thanks
Adam
 

Minder

Apr 24, 2015
3,478
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I am talking about another one that is mainly a question and answer site. I also see lots of times the "best" chosen answer is actually flat out incorrect.
.

What you have to realize that many out there obtain there knowledge of a certain subject etc from the internet itself and not from a formal training in the subject.
They believe it to be plausible and appears to come from someone proclaiming certain knowledge so they honestly believe it to be true.
I have ran into this situation many times, some even put up a web site on a certain subject and make statements that are patently false.
But they have acquired this from other sites who are also in possession of the false info.
The web can be an asset and a curse.;)
M.
 
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