Active balancer advice required

[toms]

I’ve only personally seen one fail in a mode that drains cells, it wasn’t a heltec - it was a few years old before it failed. I’ll try to find a photo of the unit type for you

I have heard of several others failing in a similar manner - enough to stop me leaving one connected full time.

I’m also curious to hear if many others have had similar experiences.

 

[Steve_S]

I still have the Failed QNBBM-8s that drained the cells to 1.1 - 1.3V in the pack, I am not sure how to open it up to "see" the internal failure.
Below is a photo and the arrow points to a Bubble/Bulge which is the failed #7.

 

[ocular]

One option to consider is to add to your existing system a JK 2A active balancer that is smart and has bluetooth and is configurable to the pack that is playing up. JK-B2A16S -But doesn't have the feature to turn off/on at around 3.4V per cell (unlike its bigger brother bms/active balancer 2A JKBMS)
I have successfully used this JK-B2A16S balancer as an add on balancer on LiFEPO4 16s pack where cells 1-4 were 200mV less at pack voltage of 56V. Set delta V trigger to 20mV and left it connected for 24/7 with max charge voltage 55V on an offgrid system. Took about 60 days to bring back delta V to 10mV (at about 40 days I set delta V trigger to 10mV) No BMS triggers occurred
There are many disaster stories of leaving active balancers connected 24/7 - and this was probably what happened to my commercial 16S 300Ahr system as the supplier had tried 3 other active balancers prior to the unbalanced state my pack ended up in. My theory is that many of the non smart capacitance type of active balancers have a poor algorithm- the heltec ones are rated at 5A but only do 1A at 80mV delta V. Not sure that even modifying them to turn off below 3.4 will be useful.
Anyway that was my experience with the add on 2A JK Active Balancer. This balancer's algorithm may not be successful in a pack with bad cells. But they are relatively expensive and if you were going to outlay that much you might consider as mentioned its big brother 2A JKBMS. Or for extra balancing power you could splurge on the 5A JK active balancer. Not sure how long such bandaid efforts will last, but ultimately your failing cell/s will catchup with you. There is a Neey 4A balancer that is more reasonably priced and the latest generation 3 hardware version supposedly has around 3.4v on/off enabled but uses the average cell voltage as the trigger not the first past the post method like the active balancer in JKBMS. It would be interesting for someone to test if the 4A Neey active balancer has more "balancing power" than the 2A Jikong balancers.

 

[Samcat]

One option to consider is to add to your existing system a JK 2A active balancer that is smart and has bluetooth and is configurable to the pack that is playing up. JK-B2A16S -But doesn't have the feature to turn off/on at around 3.4V per cell (unlike its bigger brother bms/active balancer 2A JKBMS)
I have successfully used this JK-B2A16S balancer as an add on balancer on LiFEPO4 16s pack where cells 1-4 were 200mV less at pack voltage of 56V. Set delta V trigger to 20mV and left it connected for 24/7 with max charge voltage 55V on an offgrid system. Took about 60 days to bring back delta V to 10mV (at about 40 days I set delta V trigger to 10mV) No BMS triggers occurred
There are many disaster stories of leaving active balancers connected 24/7 - and this was probably what happened to my commercial 16S 300Ahr system as the supplier had tried 3 other active balancers prior to the unbalanced state my pack ended up in. My theory is that many of the non smart capacitance type of active balancers have a poor algorithm- the heltec ones are rated at 5A but only do 1A at 80mV delta V. Not sure that even modifying them to turn off below 3.4 will be useful.
Anyway that was my experience with the add on 2A JK Active Balancer. This balancer's algorithm may not be successful in a pack with bad cells. But they are relatively expensive and if you were going to outlay that much you might consider as mentioned its big brother 2A JKBMS. Or for extra balancing power you could splurge on the 5A JK active balancer. Not sure how long such bandaid efforts will last, but ultimately your failing cell/s will catchup with you. There is a Neey 4A balancer that is more reasonably priced and the latest generation 3 hardware version supposedly has around 3.4v on/off enabled but uses the average cell voltage as the trigger not the first past the post method like the active balancer in JKBMS. It would be interesting for someone to test if the 4A Neey active balancer has more "balancing power" than the 2A Jikong balancers.

Have run it for little time and Neey is not going to push full current to balance like JK balancer. JK has patent protected algorithm that will balance up to full rated current even when delta V is down to 5 mV. So far that I'm aware from Chinese brands all balancers do fall on current when deltaV gets tight except JK . And I'm going to put it to the test when they arrive. I have ordered JK BMS ...JK balancer 5A and 10A . And if it pass all torture tests i will try to make custom order with ability to turn on and off without removing leads connectors every time.

 

[ocular]

Have run it for little time and Neey is not going to push full current to balance like JK balancer. JK has patent protected algorithm that will balance up to full rated current even when delta V is down to 5 mV. So far that I'm aware from Chinese brands all balancers do fall on current when deltaV gets tight except JK . And I'm going to put it to the test when they arrive. I have ordered JK BMS ...JK balancer 5A and 10A . And if it pass all torture tests i will try to make custom order with ability to turn on and off without removing leads connectors every time.

Interested to hear your initial results of your experience with the Neey. It's rated with 4A balance current but sounds as though it may not be as powerful at balancing as the JK2A balancer - both seem to have a cycle with charge pulses. This will be useful to document for other users. Some users complained that the Neey balancer would not switch off when run balance was toggled in the bluetooth app. Apparently on initial setup the default mode is not to allow balancing to be switched off until balancing down to a set delta V had happened . No sure if this was noted in your generation 3 Neey. With your purchases you will be able to do some interesting comparisons. These types of active balancer should be much more efficient as other balancers seem to rely on the magnitude of delta V to drive current. The heltec capacitor type say only 1A at 80mV.
I would be keen for you to observe if the balancing algorithms of the JKBMS and the standalone JK balancers are the same (JK balancers dont turn off/on around 3.4V) and to observe balancing performance of JKBMS with delta V only compared to using delta V as well as on/off around 3.4V. Much to learn.

 

[Warpspeed]

Shifting one amp at 80mV voltage difference is quite good.

Have to laugh when I read about five amp balancers and ten amp balancers, its typical Chinese fake advertising B.S.
Like those shoe box sized inverters that can produce 80 Kilowatts of advertised ac power from a 12v battery.

Think about it.
If you were to connect two cells in direct parallel that have an 80mV voltage difference, with an 80 milliohm total series resistance, you should get that one amp of current flow.
Now technically you can use either inductors or capacitors to do the energy transfer, and these work by pumping energy packets which can ONLY be current ramps that work at a 50% maximum duty cycle.
To transfer one amp requires a current that ramps from zero to four amps over half the total time, then recharges, to produce an average one amp average current.

Now we are looking at a four amp peak current with only an 80mV voltage difference. Total series resistance to do that can be no more than 20 milliohms. That includes the switching mosfets, any dc wiring and pcb circuit tracks. There will be two mosfets in series in the current path, one to charge the capacitor (or inductor) and the other to transfer that energy into the second cell.

That is an entirely practical expectation and with care, not too difficult to achieve.
One amp at 80mV difference.

So the advertisers claim to offer a five amp balancer. But they don't say at what voltage difference you must have to reach that five amps.
It might be one cell has to be at 2.0 volts, and another cell at 3.65 volts.
At more realistic voltage differences, the actual current transfer might be pretty weak, and nothing like five amps people expect and have paid for.

So the whole thing is pretty much a joke.
Once you get seriously into the design of active balancers, it soon becomes aparant that to do it properly requires components a lot physically larger than you see in commercial balancers. Even the wimpy little wires you get in the kit will add singificantly to series resistance, and make the advertised claimed performance highly unlikely.

 

[time2roll]

Last I read it was close to 500 mV to get the 5 amp rating. The 80 mV would be less than an amp.
Not going to change much while watching. Over a week or more everything should be moving into place.

I think NEEY has a balancer that does 4 amps regardless of spread but made for higher voltage (48+?) batteries.

 

[TheGreenThing]

Do we need active balancing during discharge?
I have a 16s with a voltage detection controller
Trigger set on at 53.6V then trigger off at 51.2v dod

My question, should the balancer turn off when charging stops?

This active balancer really help my pack to be balance during charging and my pack seems better ever since i installed an active balancer.. my pack was suffering from one cell hitting ovd 3.6v then other cells are unable to take a more charge then also hitting LVD too early at 51.8v pack voltage

Does active balancer help during discharge or should i just turn it off after charging

 

[740GLE]

IMO soon as cells are under 3.4v balancing isn’t needed.

Some feel balance all the time is the best. I guess it all depends on how the battery is used, constantly between 20%and 80% or always between 80% and 100%.

 

[Warpspeed]

Do we need active balancing during discharge?
I have a 16s with a voltage detection controller
Trigger set on at 53.6V then trigger off at 51.2v dod

My question, should the balancer turn off when charging stops?

This active balancer really help my pack to be balance during charging and my pack seems better ever since i installed an active balancer.. my pack was suffering from one cell hitting ovd 3.6v then other cells are unable to take a more charge then also hitting LVD too early at 51.8v pack voltage

Does active balancer help during discharge or should i just turn it off after charging

We fully recharge our cells each day, or at least try to.
Cells cycle between full charging voltage, and to something much lower down the discharge curve at night.
Now each of our cells might have a slightly different amp hour capacity, and this difference may grow after long usage.

To overcome these cell capacity differences, and get the most from the whole battery, we top balance.
We make sure that all the cells charge up to the exact same voltage.
During discharge the cell voltages diverge, sometimes by quite a lot. If the balancer is still running, it can mess things up, and undo the good work.

We really only want the balancer to run when the battery is fully charged and at full charging voltage. As soon as we start a discharge we should really switch off the balancing function, because it can then do more harm than good.
Some people have different ideas about all this, but the consensus seems to be, that for solar applications, top balancing only is best.