Li-on battery charger

[ertansuluagac]

Hello everyone
I want to charge 2200mA li-on battery. I am looking for a sensitive and heat-resistant circuit. Does anyone have any suggestions?
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Es

[temtronic]

It will be cheaper to buy a premade charger than building one with a PIC. Also a LOT safer !

[Ttelmah]

A huge amount also depends on what you actually want to do?.
Fast charge or just a slow charge?.
How is the source supply generated?.
One cell or more?.

For one cell, something like the MCP73827 is a typical device. Choose
the version (-4.1 or -4.2) according to the specified charge voltage for
your cell.

[gjs_rsdi]

Hi ertansuluagac

If you will make a search on the internet for lithium ion battery charger circuit you will find many examples.

I will also take Temtronic advice and buy one.
From the web:

[Ttelmah]

Yes. A good charger circuit needs several things:
First an accurate voltage reference. You want something in the order of 1%
or better.
Then remember this is only going to give this accuracy if the resistors
etc., used to form the potential divider are at least this good.
Then you have to limit charge rate based on current, but also cell
temperature. A cell that is sitting at 40C, cannot be charged as fast as
one sitting at 10C.
Then you should not charge Li-Ion batteries below 0C, and you have to again
reduce the charge rate when the cell temperature is below 5C. The actual
chemistry becomes less and less able to recombine oxygen and hydrogen
when the cell temperature falls. Car batteries actually have heater blankets
to warm the cells when they are too cold to charge at normal rates.
The full charge temperature range for Li-Ion, is 5C to 45C, but you get
better life if you reduce the charge rate below 10C, and avoid the very
top of the temperature range (remember the sensor is not physically
inside the battery itself....).

Tesla use a series of separate sections in their batteries, and reduce
both the charge and discharge rates on sections as their temperature
changes. It's the only way to support the high charge and discharge
currents without damage.

[temtronic]

I had 'fun' the other day and tore into a Ryobi18+ battery pack. Yikes ! A double sided PCB covered with itty-bitty parts !! The pack consists of 5 individual Li-Ion batteries, one of which was 'dead'. Since can't import new ones from China, I 'zapped' the one bad cell enough to get it above the 'dead cell' threshold. That gamble paid off... Ryobi charger saw it as being ok and it recharged.
There HAS to be a LOT of sensors and algorithmns and 'math' to recharge these batteries. I suppose once it's all figured out for one cell, they just copy the program for every cell in the pack. Not an easy task ! If it's just one cell, I can buy a complete charger for $2 CDN...that's about a minute of my R&D charge rate ($100/hr).

[Ttelmah]

Keeping a multi cell pack properly balanced adds another complexity.
Problem is that while conventional batteries have their internal self
discharge rise as they approach fullly charged, these don't. They will
merrily carry on charging past the point where the cell becomes
damaged. They can then go into thermal runaway. Really fun!...
Because of this lack of self balancing, if you appled a nice 2* voltage
across two cells, and one got fully charged before the other, this one
can then become overcharged. Disaster. So you have to control the
charging voltage of each cell individually.
With a single cell, you can just turn off the voltage feed, but with
multiple cells the problem is you need to carry on feeding voltage to
the other cells, while ensuring the one that is already charged doesn't
charge any more. So what is done is a bypass FET is turned on to
prevent the cell charging any more....

It's worth perhaps adding that the A123 Lithium Iron Phosphate cell
type does self balance at low charge currents. So provided you are
happy to only charge at 0.1C, these cells can be used without all
this complexity. However these cells have a slightly lower energy
density than the normal Li-Ion cells. The highest energy density
of all, is the Lithium Nickel cell. These
are fabulous, and with a good charger/balancer, can give something
like 25% more power per Kg than anything else.