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20s 24s tiny balancer for 15usd that can fit in your pocket.


alcatraz

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Just wanted to let you know of a neat little balancing circuit that I saw here in China.

It's based around the ETA3000 circuit that you can google.

I haven't tried it myself. But it appears that you could hook it up whenever needed or leave it connected and just use the wheel normally. It doesn't require any power supply and it doesn't balance by discharging all the highest cells (lots of heat).

I suspect the reliability isn't the best so perhaps it isn't a good idea to leave it connected and forget about it. 

These provide 0.6-1A balancing current (per cell group) and they're superefficient so they don't get hot. Pretty neat.

1611552871168.jpg

Edited by alcatraz
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  • alcatraz changed the title to 20s 24s tiny balancer for 15usd that can fit in your pocket.

Interesting @alcatraz, it's an active balancer right?

I know active balancers are sometimes used in high drain, harsh environment applications where it becomes useful to balance cell groups as they can get unbalanced significantly during a single usage cycle.
And thinking of it: it could apply to EUCs, like when riding at high speed in -5℃ or lower, draining the whole back in an hour or less.

However all the reviews of active balancers I've seen so far (YouTube videos) seem very critical of the active balancers they were testing for DIY power wall applications.
It looked like the balancers were not doing what they claimed, and on top of that it was probably not the right application anyway.

What do you think, will you try?
It would certainly be interesting to test it extensively before attaching that to a pack.
Depending on this board's efficiency and where it would be placed, it could create heat affecting some cells and not others leading to premature ageing of some of them - ever increasing the need for balancing.

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I saw a youtube clip showing how it works (jump to 7:25). Yes I believe it's active. It takes charge from the higher voltage neighbouring groups, charges a coil and then dumps it into the lower ones. It seems that it can actually get some pretty decent balancing currents this way. Not 30mA like some BMS boards out there, which is useless for high capacity cells.

I've seen specs that it stops at 0.03v difference and starts when there's over 0.1v. I argued with the seller that in a 24s scenario you could end up with 4.2v on group1 and 0.03x23=0.69v lower voltage on group 24 (3.51v). He got annoyed with me and said that's extremely unlikely.

 

 

 

Edited by alcatraz
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1 hour ago, alcatraz said:

It seems that it can actually get some pretty decent balancing currents this way. Not 30mA like some BMS boards out there, which is useless for high capacity cells.

If you mean the currently used boards with the "30mA like some BMS boards" they have "just" a different technology - passive balancing. They are by design not intended to balance much bigger currents.

1 hour ago, alcatraz said:

I've seen specs that it stops at 0.03v difference and starts when there's over 0.1v. I argued with the seller that in a 24s scenario you could end up with 4.2v on group1 and 0.03x23=0.69v lower voltage on group 24 (3.51v). He got annoyed with me and said that's extremely unlikely.

Lol!

From reports here it seems that battery pack aging means that one (or just sometines two) paralleled cell groups start to get out of sync.

The opened packs showed this cell groups having less voltage - the other cells beeing quite similar.

So with such an active balancer one would create exactly "your annoying and extremely unlikely" scenario! ;)

Just the imbalanced cell is more likely somewhere within the pack and not at one of the two ends...

Another point to regard imo - depending a wheels power and battery config most should be quite extreme in regard to discharge current per cell! Exactly in such high burden situations the voltage differences get bigger and the active balancer would start and so additionally burdens some cells... No idea if this additional max 1 ampere could be noticable/counterproductive while one burdens the wheel.

At longer "breaks"/storagr with one bad/not so good cell group the pack could constantly charge this cell group. 

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