Daisy chain active balancer

[chronosgarage]

Have anyone here have an experience with daisy chain multiple active balancer board?

I bought this active balancer 1.2A 2s-4S. I’m thinking of using 5 pieces of this balancer in daisy chain for my 20S9P li ion. Will the daisy chain cause all of the active balancer to balance all of the parallel cell group?

Will this setup work? I appreciate any help.

 

[_GonZo_]

I have seen them as well.
I am interested as well in knowing how they work.
Usually when referring to active balancing means that they move "charge" from the high voltage cells to the low voltage cells in order to balance the pack. (what I think is great)
But I do not see how this simple circuit can do it.
If someone knows how they work can enlighten us?

 

[chronosgarage]

I have seen them as well.
I am interested as well in knowing how they work.
Usually when referring to active balancing means that they move "charge" from the high voltage cells to the low voltage cells in order to balance the pack. (what I think is great)
But I do not see how this simple circuit can do it.
If someone knows how they work can enlighten us?

If there is more than 0.1v difference between the parallel cell group the board will transfer the highest parallel group voltage to the lowest parallel group until every parallel cell group is equalized. The tolerance is 0.03v, which is very good.

 

[eMark]

Would be an advantage if it was such (stand alone) that it was adjustable for either bottom balancing, middle balancing, top balancing and/or additional option adjustment for even when the battery is at rest (after bottom discharge or after top charge) . Owner has option which function to use and for how long depending on condition of battery and option preference. Even an option setting for when the battery pack is at rest for any extended period to track self-discharge rate with p-group digital readouts a must.

Long overdue to keep a check on overall health of battery pack to prolong life for discriminating DIYers. Finally a true BMS. The drawback as usual would be its degree of accuracy (dependable reliability) and price. For most ebikers it would be too expensive, and possibly too much bother. Also possibly not necessary with top brand name new cells, good DIY battery asssembly and little, if any, battery abuse.

Perhaps as has been said before ... the only use of an affordable BMS (BPS) is for Protection, not Maintenance.

 

[_GonZo_]

If there is more than 0.1v difference between the parallel cell group the board will transfer the highest parallel group voltage to the lowest parallel group until every parallel cell group is equalized. The tolerance is 0.03v, which is very good.

I know what an active balance board is suppose to do.
What I do not understand how that simple board with out any capacitors, switching mosfets, programable chip, etc. can do it.
Have you test it? Does any of the components get hot when doing balancing?

 

[_GonZo_]

Would be an advantage if it was such (stand alone) that it was adjustable for either bottom balancing, middle balancing, top balancing and/or additional option adjustment for even when the battery is at rest (after bottom discharge or after top charge) . Owner has option which function to use and for how long depending on condition of battery and option preference. Even an option setting for when the battery pack is at rest for any extended period to track self-discharge rate with p-group digital readouts a must.

Long overdue to keep a check on overall health of battery pack to prolong life for discriminating DIYers. Finally a true BMS. The drawback as usual would be its degree of accuracy (dependable reliability) and price. For most ebikers it would be too expensive, and possibly too much bother. Also possibly not necessary with top brand name new cells, good DIY battery asssembly and little, if any, battery abuse.

Perhaps as has been said before ... the only use of an affordable BMS (BPS) is for Protection, not Maintenance.

This is just a balancing board not a full BMS :wink:

 

[chronosgarage]

I’m using this balancer board together with my 20S 80A BMS. Just for balancing purposes, the safety features is handled by the bms.

 

[thepronghorn]

If there is more than 0.1v difference between the parallel cell group the board will transfer the highest parallel group voltage to the lowest parallel group until every parallel cell group is equalized. The tolerance is 0.03v, which is very good.

I know what an active balance board is suppose to do.
What I do not understand how that simple board with out any capacitors, switching mosfets, programable chip, etc. can do it.
Have you test it? Does any of the components get hot when doing balancing?

The little 6 pin ICs use the inductors to transfer current between cells to balance them.

 

[chronosgarage]

The problem is i bought the one without any indicator. So there is no way i can visually tell if the balancer works or not.

I’ve tested with a group cell that have more than 0.1v difference, it become warm and the voltage gap becomes smaller.

I bought another set of 5 pieces balancer with led indicator.

 

[district9prawn]

I believe the problem with these switched inductor and capacitor balancers is that the balancing current is proportional to the voltage difference. So my understanding is that the balance current tapers off and it gets quite slow as the cell voltages get closer.

 

[chronosgarage]

I believe the problem with these switched inductor and capacitor balancers is that the balancing current is proportional to the voltage difference. So my understanding is that the balance current tapers off and it gets quite slow as the cell voltages get closer.

I think so too, just like a charger.

 

[_GonZo_]

I believe the problem with these switched inductor and capacitor balancers is that the balancing current is proportional to the voltage difference. So my understanding is that the balance current tapers off and it gets quite slow as the cell voltages get closer.

I did a small research on that small balancing boards and they are only able to move energy from one cell to the adjacent cells. And they are not so efficient as the capacitors ones as they heat up quite a lot. So cheap solution for small and low S count packs.

I was interested in this because:
I designed long ago provably the first active balancer in the world, check here: https://www.diyelectriccar.com/threads/new-bms-technology.39249/#post-154178
Due to financial reasons we where not able to develop it, so others took over it and now it is a quite common product.

We used capacitors to do the energy transfer and it was quite impressive how much and how fast we could move energy from ones cells to anothers. And yes, as the voltage difference was getting smaller the current dropped and actually that is the appropriate way to do it. And not a problem because when difference is small (<0,05V) there is no risks of overcharging or over discharging. (And that can be taken care by the control unit as well)
The balancing boards we made didn't heat up at all, even when transferring its maximum power from ones cells to others.
And they took energy proportionally from the highest voltage cells and deliver it to the lowest voltage cells proportionally as well, no matter how manny cells in the pack or its position in the pack.