Active balancing, any good?

Wond3r if anybody has experience with this, and is it any good, sounds pretty good

?7.03 32%OFF | 1.2A Balance Li-ion Lipo Lifepo4 LTO Lithium Battery Active Equalizer Balancer Energy Transfer BMS 3S 4S 5S 6S 7S 10S 12S 13S 16
https://s.click.aliexpress.com/e/M5JnhTAY

Thanks

Yes they can work and you can on very unbalanced uneven pack gain some energy or save some BUT...

1. You dont know how much have been balanced and therfore you don tknow if you have issues.
2. On uneven packs you will be transfering energy back and forth all the time where you might not even need to...
3. You still need a BMS.

So Active for sure have its places but for most powerwalls with 2nd hand cells i wouldnt consider it the first choice.
They are also a lot more expensive.

I have one of those boards and yet to try it out, although it does not look like an active balancer due to the circuit components used.....

One type of true active balancing unit is powered by the pack as a whole and then passes/charges the lowest cell in sequence (one at a time) and the tell tale sign of this approach is a separate (fully isolated) DC-DC converter and a common switched DC bus to the cells. These boards lack that approach so looks like just isolated balancer circuits.

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Hugely agree on point 2

Every pack with small unbalanced/mixed cells should only be actively balanced for a set (possibly narrow) voltage range, otherwise you will just end up charging/discharging cells for no reason. Read the parallel cells testing theads Wolf is performing.

I bought 2 of those (4s version), I connected one to a severely out of balance pack, the lights were blinking but after 5 hour connected pack was still out of balance. I havent tried the other but after what I saw I have no confidence it can do the job.

Recently I bought these other balancers (Lithium Battery Active Equalizer Protection Board 4S 5A Balance Li-ion Lifepo4) , these are real small also and have no blinking lights, I connected to a 4s lifepo4 pack that was slightly out of balance and after an hour it was able to get it in balance. Its been connected to pack all week and pack is in perfect balance.These would be good for a smaller pack that isn't charged at high amps. (20 dollars for 4s). I havent fully tested them out, but so far like what I see.




If you have a pack with balancing issues, I recommend these large balancers they are expensive but they work excellent and can keep up when you are fast charging. I been using on my 4s 220ah lifepo4 pack for 2 years. (4s cost about 100 dollars). This pack always goes out of balance when charging, it always trigger the bms early. With these balancers I get a full charge everytime. Worth the cost to me.

jonyjoe505 said:

If you have a pack with balancing issues, ...

Click to expand...

you shouldn't be throwing money at it with a balancer of "any" sort and actually fix the problem. If a string has balancing issues, it's like the old cartoons where there's a leak in a dam and they patch it with bubble gum. This stops the leak for a brief moment. In the end, the whole thing comes tumbling down if the "real" problem isn't fixed.

These were the larger tenergy 32650 cells 5.5ah, total 160 cells. I never did a capacity check on the cells since they were new straight out of the box, I just check for proper voltage. I didn't have the holders to test every cell. I read that these tenergy/fullriver brand lifepo4 are known for balancing issues.

18650 next to 32650




Total of 4 of these make up the 220ah lifepo4 pack, except for the balancing issues when charging, it worked great. For me it was too much work to take apart to find the weak cells. And to do it right I would have to test all 160x 5.5ah cells for capacity, the active balancers solve my problem. For 18650 packs I build I always test for capacity/self discharge rarely have balancing issues.




But active balancers also help packs that are in balance especially if you charge all the way to 4.20 volts. I notice my 18650 packs as they get near a full charge one of the cells will start to charge faster then the others and trigger the bms early. The built-in bms balancers only bleed at 60ma, the extra help from the active balancers might be enough to get you a full charge.

Active cell balancing works, and so do passive ones. I use these https://www.aliexpress.com/item/32816488046.html and I have done some test on single cells https://secondlifestorage.com/t-The-Outhouse-Powerwall?pid=35049#pid35049 so it works for me. I like the active because it doesn't require set points to bleed like passive so its balancing during charging and discharging, and not top balancing or bottom balancing only like passive ones do. It stops balancing at under 30mV so the deviation for my cells are never more than that, and the balancer is mostly idle.

A properly built pack should not require much balancing. If a balancer cannot keep up with the balancing then you have an issue with the packs. My packs were left without a balancer for 3 months and it never deviated more than 100mV. I also keep between 85%-15% discharge so I'm in the sweet spot on the curve where it's fairly linear.

The one thing like daromer says is that it is not a bms. Fortunately the one I have had a serial display to allow me to capture the data. This allows me to graph and alert so it will trigger commands through a raspberry pi. In essensce it turned into a bms.

Thanks interesting, maby these will be good on a new cell pack where it should be balanced well
Was going to use this on a small 12s8p pack for an electric skateboard.

On a pack with new cells you should not have to balance. = Waste having active balancer.

Active balancer is generally used on packs where you have high uneven wear and where cells constantly drifts OR when you need to utilize all energy you can meaning you need to transfer it.

A pack that doesnt stay in balance most time of use should be considered having issues.