cheap 24V LiFePo4 charger with a balance port - where to buy?

[Just]

Hi All,

I'm seeking for a cheap 24V LiFePo4 charger with a balance port. Any suggestions?

Thank you!

[Lollandster]

I'll refer you to the same site I did last when you asked for a 24v charger. www.hobbyking.com

[Just]

Have you finally bought one from them?

Actually the chargers on this site work from 10-18V input voltage. But I need one, which would work from 220V.

BTW, do the chargers with a balance port charge each cell separately? Because if a battery is charged with a bulk charger and BMS then all the cells are charged simultaneously with the same current and only when one of the cells reach its top voltage/capacity, the BMS cuts off the charger input and only then starts the balance process. But, how does it happen with the charger with a balance port? Is the process the same?

Thank you

[Lollandster]

There are some chargers there that do 220V input. This for example
And they do sell Power supplies too.

[Morgen 3Eman]

Hi Just,

You need to read some specs more closely,  my GM battery bms balances the charges while charging by bypassing the charge current around the cells which reach full charge soonest.

By the way, what is a "Balance port"?  What does it do?

TTFN,
Dennis

[Just]

Dennis,

Where can I read the GM BMS spec? Do you have it?

The Balance Port is an additional output from some chargers. From my understanding, it's used to charge the battery cells separately.

Please let me know regarding the BMS spec.

Thank you

[Morgen 3Eman]

Hi Just,

I saw a circuit schematic for a section of the GM BMS somewhere, but I honestly don't remember where.  It was probably on this site somewhere.  You could do a search for it.

Regarding the balance port usage, am I to understand you would have to connect a pair of wires to an individual cell within the battery package?  That seems terrible clumsily to me.  And fraught with danger. 

TTFN,
Dennis

[Just]

this is the reason why I'm trying to figure out how does the Balance Port work.

[Cornelius]

Battery packs with BMS doesn't need a charger with balancing port, because the BMS does the balancing during charging. (Or after the charge; depending on how advanced the BMS are.)

For a battery pack without a BMS (One you made yourself with 8 LiFePo4 cells, for example.), you should use a charger with a balance port for 8 cells. There would then usually be 9 thin wires going between each cell from the balance port, in addition to 2 heavier wires for the charging itself.

One type of balancing use the extra voltage from fully charged cells to top up cells that are less charged to equalize them; usually after the main charge are finished, and the more advanced balancing, actively charges or discharges cells individually during the charge.

[Just]

Cornelius, thank you for your comments.

Could you help us and tell where is possible to purchase such advanced BMS, which is able to balance the cells during charging? What's balance current in this case?

Thank you

[Cornelius]

I have no company to suggest.

Balance current are usually 75-90mA...

[Just]

Balance current are usually 75-90mA...

Also when the balance is done during charging the battery (advanced BMS as you described in your previous post)?

[Cornelius]

Maybe I should be more precise; balance current should be  no more than C/100, so the above figure are suitable for 8-10Ah cells. Balancing happens usually after the Constant Voltage (CV) stage; during 'the topping up the last bit' stage.

Wether the balancing happens during the last charging stage or after the charge; the important point is that it happens. The only real difference between the two mentioned methods are that those BMS that balance after the charge tends to leave the battery 98% charged (atleast not 100%), which really doesn't matter...

I had an outburst here over a year ago concerning the naming of 'BMS'... 

Listen guys and girls...

I think it's time for a cleanup of acronyms and expressions here...

First, you all use 'BMS' for electronics that manages the battery in any way... There are at least 3 different battery management systems:

PCB/PCM - Protection Circuit Board/Module
These are the basic boards, preventing overcharge and overdischarge; some also have balancing function and max.discharge current protection. Price from $10 and up...
This is what GM batteries use!!!

CMB - Charge Management Board
These are a bit more advanced than a PCB/PCM, often with balancing function, fuel gauge and charge-while-discharge capabilities in addition to basic PCB/PCM functions. Price range from $40 and up.

BMS - Battery Management System
This is the most advanced system which monitors and controls everything, and then some; also the most expensive - usually $400-$500 and up...

And second...
You say LiPo... What chemistry?!?!
Are we talking about LiCoO₂ specific, or any Li-Ion cells with Polymer casing?

There's a jungle of different chemistrys out there; all with advantages and disadvantages, so it's important to be precise when discussing and recommending cells...

Later, I have also learned that CMB sometimes just manages the charging in a larger BMS system...