In the past I've used a lot of "damaged" Li-Ion cells from a friend which
was selling phones accessories. The damaged cells are usually usable if the
defective charging circuit is removed from the accumulator. The cell is
still good even it's voltage dropped down to 0.6V-1V for quite a long time.
You can do nothing if the voltage drop down to 0.0V. The cell is then
disposable.
I've noticed some circuits inside the cells limit the voltage using just a
zener diode instead of a management IC.

So, charge the Li-Ion cell using constant current (not voltage) and limit
the voltage on the cell at about 4- 4.1V by lowering  the charging current.
This method will not let you charge the cell 100% but will keep your cell
alive for a long time.
I have a few prototypes which works great after some years using this
method.

good luck,
Vasile

On Sun, Apr 24, 2016 at 6:20 PM, Jason White <
whitewaterssoftwareinfo@gmail.com> wrote:

> Hello,
>
> I'd like to design a simple lithium Ion battery charger for my own use. I=
t
> does not have to be fast, elegant, or pretty. As I understand it, Li-Ion
> batteries are normally charged with a constant current until the battery
> reaches a cutoff voltage of ~4.15 volts. After the cutoff is reached a
> constant voltage is maintained until the battery is removed.
>
> However, in my case I don't particularly want to use a dedicated charger =
IC
> or a microcontroller to manage the charge cycle. So my question is: would=
 a
> fixed voltage (perhaps 4.2V, current limited through a resistor) be
> suitable for charging a lithium ion battery?
>
> The only disadvantage of this that I can see is that charging will be
> significantly slower and a full charge may not be achieved in a
> "reasonable" amount of time.
>
> --
> Jason White
> --
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