[SOLVED] charging of 7.2V (couple of cell 3.6V combined) circuit

Dear all
I have Laptop cells of 3.6V rechargeable.
I am using these cells in my circuit.
now I want to design its charging circuit
cells are combined to produce 7.2v.
Is 9V 2A adopter is good for these cells for charging ?
should I only add a diode between charging point ?
any suggestion please

yes I think a diode will be sufficient for charging circuit.
you must add LM3914 for charge complete or low level of supply.

good idea from kashif_gg
add areference LEDs for charge complete or low battery

LM3914 is not better solution
read this for details
https://www.edaboard.com/threads/235959/

thank you all
any other suggest will be appreciated please

3.6V cells ... are they lithium ion/polymer? Are they 18650 size? Do they have a built-in (on the end) protection PCB or have you removed them from the protection circuits in the original battery pack?

These cells can be very hazardous. If you are thinking of simply using a diode and low voltage adapter, like is possible (but not good) for NiMH cells, then you need to read about Li-ion cells and their charging.

You must not use a simply power supply and a diode!

They need very carefully controlled charging to give reasonable service life and prevent them from exploding (I do mean 'exploding' literally, with lots of shooting flames and jets of burning lithium).

Read:

Also: https://www.candlepowerforums.com/v...-using-li-ion-cells-occurs-during-re-charging

For a laugh: https://www.youtube.com/watch?v=n0M-ZX2DBxY

It's easy to charge them, but it must be done correctly. I use a lot of recycled laptop cells in flashlights for cave exploring, but am very, very careful about charging and using them.

thanks dear FoxyRick

what should I do then please suggest

---------- Post added at 08:03 ---------- Previous post was at 08:02 ----------

I have LI-ION 18650 cells

---------- Post added at 08:04 ---------- Previous post was at 08:03 ----------

3.6V 2200mAH

By far the safest (and simplest) way is to buy a LiIon charging regulator ic, something like the MAX1757 from Maxim, although there are many other choices if you search:

**broken link removed**

Otherwise, you need to make a circuit that limits and controls both current and voltage (and preferably temperature too). It will probably cost you more than simply buying a proper charging ic.

Really, while they can even be charged (carefully) with a good laboratory power supply if you watch over it like it's a baby, I don't want to advise anything other than a proper charger due to the inherent risks. If you are determined to try, read this for the basics: https://www.powerstream.com/li.htm

Understand this though: When a LiIon cell has been 'abused', that is, undercharged, overcharged, shorted, etc. then it can start to develop needle-like, metallic growths throughout its length. These can (and often do, if the cell is still used) eventually bridge from positive to negative parts of the cell. This can happen any time, even when the cell is not in use, as the dendrites continue to grow. When the short happens, the worst case is an explosion, fire and burned down building. I'm not exaggerating.

Often, LiIon cells from used laptop packs are in this state. I use a Pila cell charger and monitor things myself as well for reclaimed cells. Any that look the slightest bit dodgy (get too hot, have a low final charge voltage, take too long to charge, don't seem to last as long as they should) are discarded immediately. I often use them in head-worn flashlights, and I like my forehead unscarred!

Agree completely with Rick. Very useful and tempting to use, but too dangerous to be charged with a simple home-made circuit.

You can get excellent chargers, cheap from DealExtreme, and they ship world-wide.

Check this out, for example **broken link removed**

Regards,

Anand

you can also use this
https://www.powerstream.com/li.htm