cheap active cell balancers

goatman

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bought 2 of these from different suppliers, hook it up lights turn on and nothing happens, even after 24hrs

IMG_20211219_081118_1 (1).jpg

tried to drain the pack down to about 2.6v/cell where there isnt much capacity so you can get a big voltage difference and more accurately balance it but at 3.0v/cell all the lights turn on. theres a 3.0v turn off

so charged it up to 4.1v/cell and it balanced the pack at 4.1v and none of the red lights came on.

it seems like it only works when the battery is receiving a charge, not when idle

i actually kind of like that if it only works when charging.

anyone else find that to be true?
 
I have a similar active balancer, but the 4s version. I stuck it on a 3s lipo that was out of balance and it was balancing it, no charger connection needed. This would have been at more like 3.5V/cell. It did the job, but I think it only balances to within 0.1V.
 
If there are also any protective functions, not allowing below 3.0V is very sensible, why would you even want to?

Do you ever go that low in normal cycling?

What is their spec'd balance (burning) current rate when cell difference is 0.1V ?

Better units do not reduce that rate as the delta narrows, and afaic that is what "active" should mean. A 2+A rate helps when dealing with bigger batteries.

Some are well under 1A, which to me is pointless.

goatman said:
it seems like it only works when the battery is receiving a charge, not when idle
Well, by any definition of active that should not be the case.

So if you are happy top balancing, your voltage point where you do it, should be a little higher than where you usually charge to for normal usage cycling.

4.10V sacrifices capacity without buying any more longevity than say 4.15V

So if that last was your termination point for normal usage cycling, occasional balancing at 4.20V would be appropriate.

 
thought plating starts above 4.1v

it was bottom balancing last night but its like the pack needs to be, ACTIVE, to balance. if its just sitting it doesnt seem to do anything of significance

theres alot less capacity per 0.1v below 3.0v

if im going down to 2.5v on the lowest group , the highest might be 2.8v. which gives 0.3v difference the bigger the difference the more amp are used to balance, i think its 1amp on these boards.

you wouldnt be able to balance a pack at 3.5v where theres a big capacity bubble,there would be no accuracy
even 4.1v has more capacity than 2.7v
 
You are incorrect about mid-point balancing, that is just as valid

how they are delivered from the factory.

Only issue is, the cells will exhibit imbalance deltas both top and bottom.

NP if both charge and discharge cutoffs are handled as per cell/group voltages.

If using top balancing, that is safer if the charger uses pack voltage.

If LVC is controlled by pack-level, then bottom balancing is better.

> it was bottom balancing last night but its like the pack needs to be, ACTIVE, to balance. if its just sitting it doesnt seem to do anything of significance

yes because a cheap little balancer may take weeks to balance without the higher-voltage "pressure"

> theres alot less capacity per 0.1v below 3.0v

No there isn't, foolish to do that if you want decent longevity, plus you'd be pushing the cells out of balance, further stressing them getting them back.

But you are correct that bottom balancing is a better way to go if you really want that usage pattern.

In which case yes a lower charging termination point makes sense since at the top is where the cells will exhibit the greatest imbalance delta.

goatman said:
thought plating starts above 4.1v
No.

but voltage is only one element of a charge profile

LI chemistries need no Absorption / CV stage, so CC-only (charge to a V and stop, simple PSU + HVC) is gentler

than holding AHT until trailing current drops to a low endAmps point

initial C-rate is the third

So CC-only to 4.2V may be gentler (lower capacity utilisation) than holding 4.1V until current stops completely.

For normal cycling my reco is 4.15V CC-only.
 
just look at a discharge graph and youll see theres less capacity at 2.7v or 4.15v than 3.5v,
its more accurate to balance where there is less capacity/0.1v

LmRCMNl.png

not a big fan of charging over 4.1v, i personally believe it throws them out of balance and kills batteries :D
 
I have one of those 1.5 amp cell balancers. And thats the maximum amount of current you'll get between cells provided there is enough voltage difference between them. The current drops as the voltages get closer. I wouldnt recommend that model for any pack larger than 4,000mah. Also do not snooze or leave an active balancer unattended while its connected to a pack.

The bigger version might be better as it does up to 5 amps of balancing between cells. Got one of those too and it works well. But even that one has its limitations and is not well suited for a larger size LiFePO4 pack if you're charging and discharging it and drawing more than 5 amps. Remember with LiFePO4 its better to balance either close to full charge or close to fully discharged as thats the steeper part of the charge/discharge curve. If you're somewhere in the middle with a LiFePO4 pack the voltages can match but the SOC (state of charge) might be off by 10% or more between cells. Also with LiFePO4 you get a voltage sag under load and a (not sure what you call this), voltage increase while charging. Those LiFePO4 voltages settle once the load or charge is removed.

The thing to remember with either size balancer is they are easily damaged if any of the connections come loose while the unit is connected. Will Prowse found that out the hard way and toasted his, lol. With either size balancer always try to plug in the connector so the ground wire makes contact first.

This guy does a good job of explaining all of the ins and outs of those 5A active balancers: https://www.youtube.com/watch?v=3N0clZrjJBc
 
TrotterBob said:
Also do not snooze or leave an active balancer unattended while its connected to a pack.

Explain?

The 1.2A active balancer boards I use are rated at 25 microamps maximum current draw when they're not balancing. They're intended to be left attached, like a BMS.
 
What happens if one fails? Why take the risk if you dont have to?

https://www.youtube.com/watch?v=F1ANSl8Kp20
 
TrotterBob said:
What happens if one fails? Why take the risk if you dont have to?

https://www.youtube.com/watch?v=F1ANSl8Kp20

What happens if you forget to reattach it in time to correct a damaging imbalance? Anything can fail, but these are designed to be left in charge of cell balance. I use them as designed. I only unplug them if I plan for the pack to be idle.
 
It is equally valid to do your balancing at **any** SoC / voltage point, so long as your cutoffs are based on cell/group level sensing.

99.99% of people just do it at the top anyway, because that is easiest.

wrt a stop point of 4.1V, no harm in doing that if you don't need to utilize every scrap of capacity, but there is no gain in longevity compared to 4.15V

...

An average discharge to 3.4V can yield triple the cycle lifespan compared to 3.2V, and

going much below 3.0V is certainly foolish if you care about longevity, way to quickly murder your packs.


goatman said:
just look at a discharge graph and youll see theres less capacity at 2.7v or 4.15v than 3.5v,
I literally have no idea what your meaning is here.

But that's OK, i do not want to pointlessly argue further.

 
john61ct said:
It is equally valid to do your balancing at **any** SoC / voltage point, so long as your cutoffs are based on cell/group level sensing.

But that's OK, i do not want to pointlessly argue further.

Nor do I. But the youtubers who've tried it say balancing LiFePO4 tends to be inaccurate in the flat part of the discharge curve. And the explanation makes sense, those LiFePO4 cells can be at the same voltage but a different state of charge (SOC).

Batteries like NMC, Lipo and Li-ion should not have the same issues since they dont have as much voltage sag or relatively flat discharge curves.
 
I need 36v 10 series lithium ion do you have any links to those cheap active cell balancers?


My battery is lower by 0.30V on the far end of the charge/discharge cables its never topped up always 80-85%
 
calab said:
I need 36v 10 series lithium ion do you have any links to those cheap active cell balancers?


My battery is lower by 0.30V on the far end of the charge/discharge cables its never topped up always 80-85%

Feebay usually has them. As do the usual suspects, Aliexpress, Banggood, etc.

https://www.ebay.com/itm/402945886243
 
LOL YT is not a great way to gather accurate information.

The fundamental understanding of what balancing is, why it's done is often missing.

In fact balancing is 100% unnecessary for battery health, just ensure that your LVC & HVC are controlled by limits at the cell/group level voltages

and worst case you are just losing a small bit of capacity utilisation, that is all.

LFP, LTO makes no difference, flatness or not of the curve makes no difference, voltage sag makes no difference.

The reason you balance, is not to try to get the voltages to line up at the same SoC.

The goal of balancing, if you want to bother doing it, is simply to get the voltages lined up **at one spot** in the SoC/Voltage curve.

And what that spot is, only matters if you want one of your care devices to use pack level voltage, do not have the gear to use cell/group voltages.

If you are focused on longevity rather than maximum capacity utilisation, and are thus properly avoiding the V shoulders

e. g. cycling LFP at low C-rates between 3.1V and 3.4V

then you may not need to re-balance at all, just check it every 200-300 cycles

With LiPo and li-on, that might be between 3.4V and 4.1V

and check every 30-50 cycles since lifespan is so much shorter.

As the cells get worn out, or dog forbid you are using old scrapped cells to build your packs

then **available** capacity is drastically reduced, and balancing more frequently and using devices with higher balancing current is required.

But as that pack reaches EoL, say 70% SoH, the balancing process is not changing that fact, not delaying the time to recycle, except a tiny bit at the margins.
 
john61ct said:
LOL YT is not a great way to gather accurate information.

Clearly you didnt bother watching the video or even trying to understand the mans methodology. And attack the source arguments are not arguments at all. Just childish hand waving.

john61ct said:
In fact balancing is 100% unnecessary for battery health.

This is inaccurate as leaving any cell or cell group at a higher state of charge does decrease its capacity over time and can also increase its internal resistance. Doing so will cause those cells or cell groups to age at a faster rate than the ones left at storage charge.

john61ct said:
LFP, LTO makes no difference, flatness or not of the curve makes no difference, voltage sag makes no difference.

This too is inaccurate. LFP voltage sag makes things like charging and balancing a less than accurate procedure, unlike Li-ion and Lipo. I speak from years of experience.

john61ct said:
If you are focused on longevity rather than maximum capacity utilisation, and are thus properly avoiding the V shoulders.

Once again, inaccurate. When you balance LFP near the steeper parts of the discharge curve you get a more direct relationship between voltage and state of charge. You dont have to fully charge LFP to 3.6v per cell to realize this effect. Charging to 3.35 or 3.4v puts you solidly in the steeper part of the curve without causing additional stress on the cells and shortening their lfespan. The same can be said for discharging LFP to slightly below 3v per cell right where the discharge curve begins to drop off. Again not causing any additional wear as its considered safe to discharge LFP down to 2.5v.

Not at all the same as working with other lithium battery chemistries.
 
> leaving any cell or cell group at a higher state of charge does decrease its capacity over time and can also increase its internal resistance.

Yes this is true, but nothing to do with balancing.

> LFP voltage sag makes things like charging and balancing a less than accurate procedure, unlike Li-ion and Lipo.

Voltage sag only happens when C-rate is too high. Switch to a different chemistry if needed.

All the setpoints need to be calibrated back to "isolated at rest voltage" so LVC is much lower for high-current use cases where bounce-back is greater.

Charging is the same, at 3C and CC-only, going to 4.2V or 3.6V and-stop no holding CV, is not reducing longevity.

The key is that stopping is based on the weakest cell/group, not bulk pack level.

Thus again, nothing to do with balancing

you just sacrifice a little capacity utilisation.

TrotterBob said:
When you balance LFP near the steeper parts of the discharge curve
But I don't go near there

There is nothing important to be gained going over 3.45V in normal cycling, and **if** you want to top balance, that makes 3.50V a good balancing point.

Again, it is useless worrying about "true SoC" just get the voltages lined up at your selected spot in the curve.

> 3.35 or 3.4v

is nowhere near the steep curve, at normal healthy C-rates

and sacrificing capacity utilisation for minimal longevity gains. Which of course is fine, the ultimate would be only cycling 20% or less around the midpoint if you needed 50+ years lifespan


> Again not causing any additional wear as its considered safe to discharge LFP down to 2.5v

Safety has nothing to do with it, it is for the sake of longevity I would never even get close to 3.0V (isolated at rest) unless in an emergency.

No matter the chemistry.
 
TrotterBob said:
What happens if one fails? Why take the risk if you dont have to?
https://www.youtube.com/watch?v=F1ANSl8Kp20
:bigthumb: . . . A "cheap" BMS has occasionally been referred to as a BMurderingS. Should a "cheap" active balancer board possibly pose a similar situation as that of a "cheap" BMS ??

If you can't get a good night sleep HOT glue a little ON/OFF push button switch on the HOT side . . . :wink:
Chalo said:
The 1.2A active balancer boards I use are rated at 25 microamps maximum current draw when they're not balancing. They're intended to be left attached, like a BMS.
Seems like the only scenario when/where you'd need a "cheap" Blinkity Blink balancer board is if your pack isn't healthy due to: Abuse, Grade B cells, Pack of new/old cells costing $1 ea, salvaged cells or a frugal owner squeezing out as many c/d cycles as possible . . . :flame: . . . before the cells are safely cycled out.

Is Rudolph's bright NOSE powered by a li-po, li-on or li-fe ... Ho, Ho, Ho
 
The question I have, and I'm just throwing this out there so nothing personal, is how much real world experience have any of you had with LiFePO4 batteries? They are a whole different animal when it comes to care and feeding and they are not like Li-ion or Lipo packs even when new.

The fun starts when you're charging an LFP pack and it gets near the end of the balance charge cycle. Thats when one or two cells out of the pack start racing ahead in voltage and your rather expensive Rc hobby balance charger just doesnt have enough balance capability to keep even a small 15ah 4 cell pack balanced unless you turn the charge current way down. If that sounds oddly specific well thats because it is. Top or bottom balancing all of them beforehand makes no difference, they dont stay balanced for very long. What an Rc balance charger does is take current out of the highest voltage/state of charge cells and turn it into heat thru some internal resistors.

Farily new li-ion or Lipo packs need very little balancing even when charging at or slightly above 1C. At least the well mached Rc packs dont. If your vendor takes the time to test for capacity and internal resistance and match your cells then yours wont either.
 
TrotterBob said:
If your vendor [doesn't] takes the time to test for capacity and internal resistance and match your cells then yours wont either.
Did you mean to say "doesen't take the time" ? What vendor in the WholeWideWorld is going to test for capacity, IR and Delta OCV? Did you mean manufacturer instead of vendor? Even then a manufacturer maybe only test 1 in a 100 at most. A problem may occur during a run in which the cells are Grade B sold to a vendor. Then the vendor sells them at a price too good to turn down by a budget restrained buyer.

From the gist of your post why would someone in their right mind buy Li-fe instead of Li-on or Li-po. Yet many do ... so their must be a good reason ... Right ?
 
eMark said:
Chalo said:
The 1.2A active balancer boards I use are rated at 25 microamps maximum current draw when they're not balancing. They're intended to be left attached, like a BMS.
Seems like the only scenario when/where you'd need a "cheap" Blinkity Blink balancer board is if your pack isn't healthy due to: Abuse, Grade B cells, Pack of new/old cells costing $1 ea, salvaged cells or a frugal owner squeezing out as many c/d cycles as possible . . . :flame: . . . before the cells are safely cycled out.

My packs are made of cells that already had a working life in cars, data centers, or hospitals. They stay balanced better than typical new hobbyist packs made of vape pen cells. But do I want to put another chore on my schedule when I could attach a balancer instead and let it go to work if an imbalance should occur? I do not. I use my bikes to save time, not use it up.

So far I have not used an active balance board for what may be its best application-- hooking up a pack full of cells that aren't all in the same state of charge. A top balancing BMS would be pretty much useless for that job.
 
eMark said:
From the gist of your post why would someone in their right mind buy Li-fe instead of Li-on or Li-po. Yet many do ... so their must be a good reason ... Right ?

They are rated for 2,000 to 4,000 cycles and are much safer vs li-ion or Lipo. If they do become overcharged or suffer an internal short they do emit lots of toxic smoke but little or no fire. The downside is you'll end up with 1.4x the weight of a li-ion or Lipo to get the same range. So if weight is a significant factor and you're not too concerned with cycle life then go ahead and get li-ion or Lipo. There are other battery chemistries out there like NMC that I'm not familiar with that also have a long cycle life.

The absolute safest Lithium battery chemistry that I know of is Lithium Titanate or LTO. You can run one of those thru a band saw and it produces very little smoke and no flame. Not that I recommend anyone should test that theory, best to leave that to youtubers and/or professionals.

https://www.youtube.com/watch?v=ezCCbBnj5RE
 
Am I looking for the basic same layout for the same circuitry design?


cheap active balancer.jpg


TrotterBob said:
calab said:
I need 36v 10 series lithium ion do you have any links to those cheap active cell balancers?


My battery is lower by 0.30V on the far end of the charge/discharge cables its never topped up always 80-85%

Feebay usually has them. As do the usual suspects, Aliexpress, Banggood, etc.

https://www.ebay.com/itm/402945886243
 
TrotterBob said:
when you're charging an LFP pack and it gets near the end of the balance charge cycle. Thats when one or two cells out of the pack start racing ahead in voltage
And if you are smart, you halt the charging process before you reach that point.

If you need to utilise more capacity

(really? why? poor planning?)

then you need better quality balancing kit - start earlier at a higher balancing current rate, adjust the stop-balance to a wider delta

and **in either case** simply do not allow any cell to go beyond 3.45 or 4.15

If any of that seems difficult, either your balancing gear or cells are crap, maybe both.

With proper new cells, you really should not need much in the way of balancing gear

do not spend money on the good stuff until you have evidence it truly is needed.


 
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