# Forum: Analog Circuits Li Ion charge only with CV - what happens

Rate this post
 • ▲ useful ▼ not useful
Hi, my name is Victor. I'm german but try it in english.

I have a solarcell and an TP4056 IC for example. (I know its not good
setup). The voltage is termined by IC and the max current by resistor.
Althing work (not fine) but "ok".

My question is what happens with the 1S 18650 cell with that setup? The
CV ist ok. But there is no possibility for CC.
What changes with the 18650 for example: Lifetime? Capacity? other
difficulty?

Is a fluctuating current input so significant for e.g. NCR18650B Cell?
Why CC recomend? If you can give me a good link in german or english
with researches or information from a producer like panasonic/sony/...
would be great. Or if you have do test and could share would be really
great.
I couldnt found something like that in web.

Best regards

: Moved by Admin

Rate this post
 • ▲ useful ▼ not useful
Here are some specs of your cell:
https://www.batteryspace.com/prod-specs/NCR18650B.pdf

CC is recommended because it has the highest charge speed without
hitting a critical limit. The NCR18650B has a maximum charging current
of 1625mA. If you limit this current by a ((4.2V-3V)/1.65A) 750mohm
resistor, you get a significant lower charging rate. However low
charging rate is always good for cycle life but with a limiting
resistor, you still have a higher maximum current compared to a CC with
the same charge speed, so even if you want to limit current for better
cycle life you can have better results with CC instead of a resistor.

But in your case, the TP4056 has a CC setting. You can set it over a
resistor. Also, you can check the maximum current which the solar cell
can deliver. If this current is not higher than the rated charge
current, there is no need to limit it afterward.

Rate this post
 • ▲ useful ▼ not useful
David W. wrote:
> However low
> charging rate is always good for cycle life

Having a very low charging rate near the cut-off voltage might actually
decrease the cycle life..

Rate this post
 • ▲ useful ▼ not useful
vwilde wrote:
> I'm german but try it in english.

Crazy, in a German forum?

To understnd the 4056, please look fr this:
https://www.youtube.com/watch?v=wfrm6lbt8Pc

Der TP4056 startet mit Konstantstrom, wozu sonst hat er wohl den
Widerstand? Deine Frage ist ziemlich unklar.

Rate this post
 • ▲ useful ▼ not useful
The cell doesn't care if the charge current is variable. The "CC" just
means limiting the current so that neither the Charger nor the Cell is
outside of its specification. For the cell that usually means 0.5C to
get the nominal cycle life.

### Reply

Entering an e-mail address is optional. If you want to receive reply notifications by e-mail, please log in.

### Rules — please read before posting

• Post long source code as attachment, not in the text
• Posting advertisements is forbidden.

### Formatting options

• [c]C code[/c]
• [code]code in other languages, ASCII drawings[/code]
• $formula (LaTeX syntax)$
 Name: E-mail address (not visible): Subject: Searching for similar topics... Attachment: Note: the original post is older than 6 months. Please don't ask any new questions in this thread, but start a new one. Text: