BMS vs. Balancer: Are They the Same? Differences, Purposes & Function Explained

Hello,
Are BMS and balancer the same thing?
If not, what is the purpose of these two elements?
Probably a simple question, but it's hard to find accurate information on the Internet.
Regards

Hello
BMS - Battery Management System, so it's the same thing.
Regards

This is not the same.
The BMS is the entire "system" used to manage cells/cells, i.e. it monitors and supervises its condition, and the key elements of its operation are: it prevents the cells from being overcharged, ending the charging process, and it cuts off the power supply system in the event of a voltage drop below a certain value on the cell (or any of the links). Briefly. The balancer, on the other hand, is an additional functionality that the BMS may or may not be equipped with. When it comes specifically to e.g. Chinese BMS modules for LION cells, they do not have a balancer function. By charging 3 cells in series (3S module) they are charged with one voltage for 3S. If one of the cells reaches the limit voltage, the system cuts off the entire charging process and the others do not charge either. The functionality of the balancer in such a BMS is such that 3 cells, although they are connected in series, are charged each separately.
The information on the net is quite accurate:
https://en.wikipedia.org/wiki/Battery_management_system
https://en.wikipedia.org/wiki/Battery_balancing

Thank you for your comprehensive answer!
So when creating a 4-cell power bank, I should use a balancer and BMS? Are these charger modules based on TP4056 just such BMS? And does this balancer need to be put between this module and the batteries?
Regards

Hello,
for some time, Chinese manufacturers (suppliers) have been offering boards under the name "BMS", which are simply "hardware secondary protection" type. Sometimes they have a "balancing" function, which, due to the embarrassingly low current, is unfortunately fictitious.

Regards

The TP4056 module is used to charge a single 3.7V cell. And only for charging.

Marcin4113 wrote:

So when creating, let's assume a powerbank for 4 cells

Do you want to connect these cells in series or in parallel?

I would like to connect in parallel to get more powerbank capacity.

Marcin4113 wrote:

I would like to connect in parallel to get more powerbank capacity.

When cells are connected in parallel, no balancing is needed.
Balancing is only needed when connecting cells in series.
Parallel-connected cells should have the same capacity, preferably of the same manufacturer and type.
Before connecting these cells (in parallel) you should charge them (separately) to as close as possible voltages to avoid the flow of equalizing surge currents at the time of connection - cells have quite a low internal resistance so equalizing currents can be quite significant.
This battery (1S4P) can be charged using the TP4056 chip (this is the single cell li-ion charger, i.e. for the 1SXP battery). Depending on the total capacity of the connected cells, charging can take quite a long time - TP4056 has a maximum charging current of 1 A.
There are also "TP4056 + protection" boards available: probably only OVC and OVD (without current protection). You should make sure that the OVC and OVD voltages are correct for your cells.

I understand now, thank you very much! One more question, if you want to make a package, e.g. 2S4P, then you will need a balancer?

Marcin4113 wrote:

I understand now, thank you very much! One more question, if you want to make a package, e.g. 2S4P, then you will need a balancer?

You will need a 2S charger with a balancing function - preferably a decent, reliable and decent one. Chargers are very well known and reviewed by colleagues from the modeling department.

krzysiek_krm wrote:

Marcin4113 wrote:

I understand now, thank you very much! One more question, if you want to make a package, e.g. 2S4P, then you will need a balancer?

You will need a 2S charger with a balancing function - preferably a decent, reliable and decent one. Chargers are very well known and reviewed by colleagues from the modeling department.

Or something like this: https://diolut.pl/balanser-4s-3s-2s-4-2v-li-i...I5xDyA8-cCCTaVLJecRUx9gzsFWXzAdBoCh-4QAvD_BwE
It's good? And how would I have to connect it?

This circuit has too small a balancing current - only 66 mA.

And what current would be appropriate? And where would I have to connect this balancer?

You can try something like DIY, for example
https://www.elektroda.pl/rtvforum/topic3255449.html
http://www.zajic.cz/omezovac/omezovac.htm
http://mdiy.pl/very-simple-balancer-do-ogniw-li-ion/comment-page-1/

The last link is very interesting, thank you. I'm wondering one thing - can you make this balancer (from the last link) so that instead of wasting heat, you can charge another battery? Is it more complicated now?

Marcin4113 wrote:

The last link is very interesting, thank you. I'm wondering one thing - can you make this balancer (from the last link) so that instead of wasting heat, you can charge another battery? Is it more complicated now?

You can do it, from the last link - not really.
It is more complicated and complex.
Look for "active cell balancing" - a system that can "transfer" energy in various directions within the battery, both during charging and discharging.

I still have a question, does the balancer also work when the cells are discharging and cause them to discharge evenly?

Marcin4113 wrote:

I still have a question, does the balancer also work when the cells are discharging and cause them to discharge evenly?

If the balancing circuits are (as in the cited links) local "shunt balancing" type (based on "shunt voltage regulator" - a "better Zener diode"), they work only during charging. There are also known lossy balancing systems (operating with relatively large balancing currents) controlled from the BMS system, monitoring the voltage of individual cells in the battery, which can discharge individual cells in any operating mode, both during charging and discharging. Typically, such a BMS implements a more or less cunning algorithm of discharging some cells also when discharging the entire battery - in order to facilitate the balancing of cells while charging the battery and generally speed up the charging process a bit.

So this is normally done by cutting off the battery when it reaches 2.5V? Because batteries certainly don't discharge evenly, something must be protecting them.

Marcin4113 wrote:

So this is normally done by cutting off the battery when it reaches 2.5V? Because batteries certainly don't discharge evenly, something must be protecting them.

This function is performed by the previously mentioned "hardware secondary protection" system. When voltage any cell reaches the "overdischarge" threshold, the entire packet is cut off. In fact, it will be cut off "partially" - you can't draw electricity from it, you can charge it.
The "overdischarge" detection threshold should be matched to the cells you have. In fact, it may make sense to use a protection circuit in which the detection voltage is slightly higher than the catalog cut-off voltage for the cell (for example, the cell has a catalog value of 2.5 V, we use a protection circuit with a detection threshold of, say, 2.8 V or 2.9 V) - disconnecting the cell at its catalog cut-off voltage, it causes a decrease in the life of the cell, in terms of the number of cycles. Equally well, you can build a system that at a voltage of 2.8 V ... 3.0 V on any cell will light up some signaling diode "time to connect the charger" or at least turn off the load.

Thank you very much for your help!