Got circuit made by questionable freelancer

Thread Starter

ejnarwj

Joined Jan 20, 2023
16
Hi everybody. I am defintely what you can call a newbie regarding electronics Recently i got this li-ion battery charger circuit with 12 v input made by a questianable freelancer, and i do not have the skills to look for errors. The circuit looks like this:
1674232889989.png
Let me know, if I forgot information about the project.
Any feedback will be appreciated.
 

Audioguru again

Joined Oct 21, 2019
5,419
A Li-Ion battery cell is 3.7V when it is sold because 3.7V is its half-charged storage voltage. It can stay at 3.7V for years in a store before it is sold. The max charged voltage is 4.20V.
Two cells in series are a max of 8.40V and are fully charged when the charging current has dropped to 1/20th the capacity.

To avoid an explosion and fire, use a Li-Ion battery charger IC instead.
 

crutschow

Joined Mar 14, 2008
31,128
made by a questianable freelancer
Questionable is right.
A proper Li-Ion charger cuts off the charge current when the battery is fully charged to prevent overcharging and possible catastrophic (i.e. fire and/or explosive) battery failure. :eek:
That circuit does not do that.
 

Audioguru again

Joined Oct 21, 2019
5,419
A Lithium battery charger circuit also senses cell voltage before charging. If the voltage is too low then the charger circuit attempts charging with a low current because if the cell is shorted with a fragment of metallic lithium the fragment will explode and catch on fire if fed a normal high charging current.
 

Thread Starter

ejnarwj

Joined Jan 20, 2023
16
Welcome to AAC!

That circuit is completely inappropriate for any lithium battery chemistry. Those batteries could start fires if abused.

Why would you use a questionable design when you can buy something for not very much money?

Here's some reputable information regarding charging lithium batteries:
https://batteryuniversity.com/article/bu-409-charging-lithium-ion
That was what i was affraid of, when ordering such things cheaply from fiverr. Maybe looking into it myself is the best solution. Will be looking at the article you sent. Thank you very much
 

Thread Starter

ejnarwj

Joined Jan 20, 2023
16
A Li-Ion battery cell is 3.7V when it is sold because 3.7V is its half-charged storage voltage. It can stay at 3.7V for years in a store before it is sold. The max charged voltage is 4.20V.
Two cells in series are a max of 8.40V and are fully charged when the charging current has dropped to 1/20th the capacity.

To avoid an explosion and fire, use a Li-Ion battery charger IC instead.
Any specific suggestions for such IC's?
 

Thread Starter

ejnarwj

Joined Jan 20, 2023
16
hi ejn

What are the details of your Li-Ion battery.
E
View attachment 285709
I apologize for using the wrong channel.

This is the specifications for the batteries i am using:

14500 Battery Item specifics :
Brand Name: GTF
Type: Li-Ion 14500
Nominal Capacity: 900mah(700-900mah)
Nominal Voltage: 3.7V
Weight: 19g±1g
Rechargeable Battery: Yes
Rechargeable Times: Up to 500 times
internal resistance: ≤60mΩ
Limited Charge Voltage: 4.2v
Working Voltage: 2.75-4.2V
Size: 14.1 mm x 49.7mm (Diameter)


Can i ask what software, you are using for that diagnostic?
 

Thread Starter

ejnarwj

Joined Jan 20, 2023
16
That was what i was affraid of, when ordering such things cheaply from fiverr. Maybe looking into it myself is the best solution. Will be looking at the article you sent. Thank you very much
The circuit was ment to be produced and incoporated in some LED products i am currently working on. That is why i can't just buy them, and why it shouldn't have any flaws :-/
 

bassbindevil

Joined Jan 23, 2014
640
But that shouldnt' be needed if multiple batteries are connected in parallel, right?
No, cells in parallel will just accept the charge they want at the applied voltage. EVs and home power banks can have dozens or hundreds of cells in parallel. Series might be a better choice in some applications; 3S is close enough to 12V to run most 12V devices, for example. In that case, use a "BMS" or "PCM" that provides protection from overcharging, over-discharging, short-circuits, and provides balancing. The buck converter chips ( SY6912, MAX745) that I mentioned provide the necessary voltage and current regulation for charging.
 
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