# How to recharge Lithium ion batteries via - simple circuit.

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I've got my hands on various discarded  li-ion batteries from laptop and
mobile phones and was wondering if anyone here knows of a simple recharger
to build ?

From some googling Li-Ion are not as easy as the Ni-Cad or niMH types and
require specific charging pattern to avoid fire or explosion.

I'm not after an expensive discrete charging chip circuitry rather something
constructed with regular op amps etc. to compare charge and cut off when
cell reaches 4.2v

There have been many cases reported that if the charging is faulty then the
laptop /ipad can catch alight.

Any recomentations/suggestions?

Re: How to recharge Lithium ion batteries via - simple circuit.

as  unserstand it you just need a current-limited voltage source.

+9V
---------[LM317]-[R1]--.
|          |
`----------+--[LM317]---X--+--->
|          |
+---[220]--+
|          |
[R2]       [1K]
|          |
---------------------------+----------+--->

a low value resistor at X slow the charging down as
the voltage reaches the set point.

--
⚂⚃ 100% natural

---

Re: How to recharge Lithium ion batteries via - simple circuit.

?
I'm not sure I understand your diagram, as the formatting was lost.

By coincidence I stumbled on a circuit by Colin Mitchell who also uses LM317
as a trickle charger to charge LI-ion.

He claims :-

"Believe it or not, you can mix any size and type of cell with this circuit
as each will become fully charged after a period of 2 days or more, without
you having to think about the situation.
You can mix any type of cells (NiCad, Li-ION, NiMH) and any size (AA, C or
D) and they will gradually charge according their own characteristics and
capacity."

See -CIRCUIT NUMBER 3: from

http://talkingelectronics.com/projects/ChargingNiMH/ChargingNiMH.html

This looks safe, but a lenghty way to recharge.

Re: How to recharge Lithium ion batteries via - simple circuit.

Yep

Basically correct.

You need to switch your reader to a fixed pitch font.

IMO the voltage regulation in Jasen's circuit is a bit rough.

(shudder!)

It is a trickle charger with a constant current.  That is fine for
NiXX chemistries where modest over-charging is acceptable and will
indeed equalise the state of charge (SOC) of a series string of cells.

Unfortunately, Lithium-based cells require a well-controlled (and
current-limited) VOLTAGE SOURCE.  That circuit will NOT provide that -
trickle charging a Li-Ion/LiPo cell will result in a progressively
increasing terminal voltage until something breaks.

In detail, sensible Li-Ion (etc) chargers provide (using as an example
the numbers from a commercial charger I designed years ago for cells
such as 18650) a 1A current limit and 4.20 volt voltage.  On initial
connection, charge current is 1A and the terminal voltage rises as the
cell charges.  When the voltage reaches 4.20, it stops rising and the
current progressively tapers off.  Usually commercial chargers will
stop charging completely when the current has tapered down to 10% of
the current limit value, although this is not critical, but the
applied voltage NEVER exceeds the target value.

Anyone using a trickle charging arrangement on Li-Ion/LiPo cells is
foolhardy.

Re: How to recharge Lithium ion batteries via - simple circuit.

Thanks.

"foolhardy"
I can tell you're being polite, unlike some here....

Re: How to recharge Lithium ion batteries via - simple circuit.

Fixed font does provide a better view. :)

Thanks

Re: How to recharge Lithium ion batteries via - simple circuit.

<<  I've got my hands on various discarded  li-ion batteries from laptop and
<< mobile phones and was wondering if anyone here knows of a simple
recharger
<< to build ?

<< Any recomentations/suggestions? >>

I use a benchtop power supply for this sort of thing.
Its an old EA 30v/1amp with current limiting.
very simple circuit, just a 723 regulator and a pass transistor with
associated circuitry and a meter.
Voltage adjustable 3 to 30v
current adjustable to 0 to 0 .4 and 0 to 1 amp
I would just set the voltage to the max level for the battery being charged
and set the current limit to a suitable amount .
As the battery charges toward the max voltage the current tapers off toward
zero.
This kit built PS has been extremely useful over the years.
Pretty old but original Altronics kit was K3210

Re: How to recharge Lithium ion batteries via - simple circuit.

Thanks  I'll have to track that down, or find something similar.