Lipo Balancer

[hadihf]

This is a Lipo balancer located at

http://www.zajic.cz/omezovac/omezovac.htm

but in Chez! Seems very simple..did somebody try it?

hadihf

[coro]

Of course. It is simple but very well device that is manufactured and stocked at local shops. I expect thousands of them that are in use daily.
Circuit does nothing below 4.2V or whatever voltage is set for, but sinks any current that is passed to Lipo cell above the voltage. Like Zener diode, but with very sharp :knee: characteristic.
However - balance cables and adapters pictured everywhere around, are way too poor to handle bleeding current. Look around... Voltage drop on such poor cable will allow the cell to go to higher voltage even if "Omezovac" is holding the voltage on its input strong.

[Skysailor]

Here's a better simple balancer:
Lithium balancer project (http://www.flyelectric.ukgateway.net/lithium-balancer.htm)

This is the one I use and it works great.

[MiseryQ]

Here's a better simple balancer:
Lithium balancer project (http://www.flyelectric.ukgateway.net/lithium-balancer.htm)

This is the one I use and it works great.I'll have to build one of those.

[yctseng]

I'd build similar one. Work fine... :)
http://www.zajic.cz/omezovac/omezovac.gif

[robin123]

this is the one I have build - 3 similar blocks

[samtheboxer]

Quick question. Will the project listed about work on a 3s 1200ma lipo?

thanks

[coro]

Quick question. Will the project listed about work on a 3s 1200ma lipo?

thanks
Yes.
There is no problem with small lipos and thus small charge currents. All circuits above should work well. Problems with such devices may start when charge current is above 3A or even much more.

[Norman Adlam]

Yes.
There is no problem with small lipos and thus small charge currents. All circuits above should work well. Problems with such devices may start when charge current is above 3A or even much more.

Hi,

Errr... your circuit seems to indicate that the 'R' and 'C' points on the TL431 are connected together (connection 'blob' on the Cathode wire going to the IC). Is this correct?

Cheers,

[David T]

this is the one I have build - 3 similar blocks

Do you have any more info on this design? Current limits, etc.
Thanks, David.

[robin123]

The original design is made by kodel:

http://www.rcgroups.com/forums/showthread.php?t=215550

It really worths to take a look on the design basis and features.

I have used it with a 1.8 Amp constant current supply to charge a 3-cell li-po pack of 1800mAh. The red LED shows a depleted cell (around 3V) and the GREEN shows 4.2V across a cell (charging completed). The 2.2 ohm resistor is used to dump the unnecessary current when 4.2V per cell is reached so the FET's don't get too hot.

The TL431 adj. shunt regulator with its reference connected to the cathode gives a constant voltage across of 2.5V which is used as a voltage reference for the inverting input of both op-amp's. This is proven by the Test figure no.2 of its datasheet.

The single thing infortunately which didn't hapen is that the red LED doesn't go off completely , but is blinking slower as the charging is completing. The reverse thing hapens with the green LED which is blinking faster when the charging is almost completed. However the voltage across the cell didn't raise over 4.2V.

This operating mode could be a consequence of my power source configuration which provides also regulated supply voltage before the current regulator. kodel used a 16V power source @ 1.5Amps feeding the balancer through a power-rated resistor which can be seen on the right of its picture, if I am not wrong.

Hope this helps. :)

[David T]

Thank you. The description and link are helpful.
David.

[robin123]

Don't mention it. If you are interested in building such a device, here it is another interesting simple design made by Suzanne:

http://www.rcgroups.com/forums/showthread.php?t=157641

[hadihf]

Hi,

The circuit in first post is just a balancer and not a charger. Am I right? Please tell me. :confused:

[DuskWolf]

yes, it's a balancer. I am using it for about 6 months now, and have absolutely no problems - works perfectly. The only tricky part is the calibrating. When you make the fine adjustments you have to measure the voltage of the battery, not on the balancer. After all the cables have their own voltage drop you have to consider.