hi, to keep a pack balanced, what are the differences between balance charger and bms(balancing bms) . is it one or the other or should be both? Lifep

[sharinginfos]

Hi
english second language here
i intend to build my first battery using 4 modules of BH below for a 16s lifepo4. short distance but up hill
i would like to have peace of mind and that battery keep balanced. once assembled, i would like to have it set and done for the rest of its life if that is realistic, you know probable more than me on that.

I dont know very well how to do that but there seems to be only 2 options for a simple setup. if other affortable options informe me. I would be gratefull.

use a 16s lifepo4bms with balancing proprieties or use a 16s lifepo4 balance charger.
wich one is best, why? is it recommended and possible to integrated the 2 together at the same time or just one of the 2 will do the job?

Could you recommend a affortable 16s lifepo4 that does balance charging(not the satiator, to expensive)?

12V MODULE WITH 8X A123 26650 LIFEPO4

Here are 12v Lifepo4 modules with 8 cells in 4s2p format. Every battery is checked and all cells will have good voltage. These packs are awesome because they line up nicely next to each other. Datasheet is in the 3rd photo. The cells are A123 power cells in 4s2p configuration.

batteryhookup.com

Thank you

 

[lnanek]

A battery with a balancing BMS only requires two wires from the charger to charge. Positive and negative. The balance wires from each p-group of cells only go to the BMS, so are internal to the battery pack. The chargers used are called bulk chargers and are cheap in general. I keep one at home and one at work. Satiator is expensive because it can be mounted to a vehicle without vibrating to pieces and can be set to not fully charge to preserve battery life.

A balancing charger requires one wire from each p-group in the battery, except maybe the last, and often a bulk positive and negative wire as well. So the charger is more complex to hookup, but the battery pack can be simpler. They tend to be used for RC/hobby vehicles rather than ebikes. It's easy to find 6s, 7s, 8s ones on eBay for $10. Ones that support the number of p-groups in an ebike battery are rare and expensive, though. There are a couple rare ones out there that support hooking up in series with a master and slave unit as well.

 

[sharinginfos]

Hi Inanek
From what i read i only one device either bms or balance charger. is that it?

what about active balancer ? in what circompstance do people use a an active balancer?

in some post i read this#and balance in a way that fits in with your normal charging routines, and doesn't force you to guess at what's going on# Would you know know what it means? Does it refer to having ways of seeing info while charging and while using? maybe even some data recording to export on pc ? what would you recommend?

#ensure flexibility in their balancing gear# Would you know how can one ensure flexibility in their balancing gear? it kind of suppost multiple ways to balance doesn t it?

thanks

 

[lnanek]

The balancing current of a typical passive balancing BMS is very tiny. Like milliamps instead of amps. It's often only a resistor for each p-group that can drain any that reach full charge ahead of the others. It turns that extra energy into heat so the bulk charging can continue and the lower voltage p-groups can catch up.

If your battery is poorly balanced, you sometimes have to leave a pack on the charger for days for this process to successfully balance. You can often see the charger blinking on and off regularly while this happens.

A smart BMS will often connect to your phone by Bluetooth and let you see the voltage of each p-group. Some will let you toggle a balancing function on manually that way too, allowing balancing to happen at times other than charging.

If the battery pack is made out of used, old, or poorly matched cells you may want more balancing current to balance faster or more sophisticated balancing methods. Instead of resistors, the p-groups can be connected with a flying capacitor to equalize charge, for example. There are also balancers that can transform voltage, so they can charge any low p-group using a high p-group or the entire pack. When not included as part of a charger or BMS, these can be added as a separate active balancer board. E.g. I have one of these that can transform voltage:

https://www.amazon.com/dp/B0B3D5JCRC

It balances a lot faster than my cell meter which can only drain high p-groups into resistors slowly so as not to make too much heat:

https://www.amazon.com/dp/B0178P8H9U

 

[Chalo]

Active balance boards typically balance cell groups better than BMS for two reasons: First, they balance at higher current, as high as amps rather than tens of milliamps. Second, they go to work balancing at almost any discharge state or cell voltage, rather than only after the pack is charged full and cells begin to hit their maximum voltages. So you don't have to charge your pack to 100% to get an active balancer to do its job.

But balance boards don't give you any of the other protections a BMS offers. Minimum and maximum individual cell voltages, minimum and maximum total pack voltage, and sometimes temperature range limits or current limits, are BMS functions that an active balancer does not provide. Some of these are functions you can build into your bike's system if the battery is dedicated to one specific bike.

If you're using old or mixed batch cells, then an active balance board is a good idea. If you're using all new, fresh, same batch cells in your pack, the balancing function built into a BMS should be fine, so long as you charge to full voltage once in a while.

A third option that you didn't address in your original question would be using a balance charger only, that brings all the pack cells to the same voltage when you charge, but isn't connected while the pack is being used. This has the advantage of simplicity, but no other protective functions. Also, balancing chargers tend to be slower than bulk chargers for any given pack.

 

[sharinginfos]

when you say #If you're using old or mixed batch cells, then an active balance board is a good idea. If you're using all new, fresh, same batch cells in your pack, the balancing function built into a BMS should be fine, so long as you charge to full voltage once in a while# does that mean that if i charge to 80 pourcent the bms will never passive balance?

with the bluetooth toggle Inanek talks about, can we leave this option On all the time so that the battery balances itself all the time even when not charging and even when cells are aroud 50 pourcent for example?

when you say#
But balance boards don't give you any of the other protections a BMS offers. Minimum and maximum individual cell voltages, minimum and maximum total pack voltage, and sometimes temperature range limits or current limits, are BMS functions that an active balancer does not provide. Some of these are functions you can build into your bike's system if the battery is dedicated to one specific bike.# does this mean that we cannot install both bms and balance board together? Active balancer seems nice but if it takes out the other feature that bms give from the battery im not sure if it is a good idea.. any way to have both?

And what about the cell meter, can it be implemented with a passive bms ?

 

[Chalo]

If you charge to 80 or 85 or 90%, a normal "dumb" balancing BMS will not reach the state where it begins balancing cells. If you use a "smart" programmable BMS, you may be able to set the balancing voltage threshold to whatever lower voltage you charge at.

You can definitely stack an active balancer with a BMS. Doing so increases the parasitic drain on the pack, to run both devices, but it has the advantage of correcting problems that might arise when the BMS powers itself from only certain cells rather than the entire pack.

 

[harrisonpatm]

with the bluetooth toggle Inanek talks about, can we leave this option On all the time so that the battery balances itself all the time even when not charging and even when cells are aroud 50 pourcent for example?

In most cases, you don't want balance to be on 100% of the time because a well-balanced pack with healthy cells should stay in balance under normal use. Even somewhat used or aged cells, when balanced before being built into a pack, should keep their balance for a decent amount of time. Balancing is something you can do to the pack every month, twice a year, ect., to keep your pack healthy and lasting longer.

So if you have a built pack that was built and assembled well balanced, and it starts to become out of balance sooner than expected, that means there's something wrong with it that needs to be addressed, perhaps one or two cells going bad fast, or a small short, or a parasitic drain. If you have an active balancer on 100% of the time, it could be potentially hiding symptoms of a failing battery, and you may not know about it until it's too late.

FYI, the BH modules you linked are probably good, but they're used and each cell should probably be individually tested. I have gotten that module and those cells from BH before, and although my sample size was small, 15% of them were bad and had severely reduced capacity issues.

 

[eMark]

FYI, the BH modules you linked are probably good, but they're used and each cell should probably be individually tested. I have gotten that module and those cells from BH before, and although my sample size was small, 15% of them were bad and had severely reduced capacity issues.

He might have to buy at least 6 hoping that at least 4 are useable for his 48v DIY build.

 

[calab]

Seems like a lot of work.
When do we look at the Lego set?

If you dont know then you should charge to 100% to ensure everythings balanced, on some regular basis when you charge short, and dont drain much. Dependent on how often you ride of course, lengths of stay in the B&B Shed. Just so many bms out there, different styles and different methodology of balancing, wheres the spec sheet?

Same goes for the charger. Go slow, buy 2 dmm's if not three.

 

[sharinginfos]

FYI, the BH modules you linked are probably good, but they're used and each cell should probably be individually tested. I have gotten that module and those cells from BH before, and although my sample size was small, 15% of them were bad and had severely reduced capacity issues.

Hi harrisonpatm, bh answered me #They are guaranteed to work as is, and all have voltage, but we don’t know the capacity of them or the history of these packs.# not sure what it implies....

when you say #they're used and each cell should probably be individually tested#.

First by individually tested, do you mean individually test each cell or individually test a 2p group that act like one cell?

Could you tell me what is the difference between individually tested with this charger https://www.amazon.com/WISSBLUE-Universal-Discharge-Capacity-Suitable/dp/B0C9CLFRJK/ref=sr_1_5?keywords=LifePo4+battery+charger+tester&sr=8-5&th=1

and the method 4s testing with a b6? B6 seems to be able to tell the capacity of cell for each of them like if individually tested no? what is the advantage of testing them individually VS using B6 machine way? Might be important.

When you say#15% of them were bad and had severely reduced capacity issues. # what do you mean by bad cell , how did you detect that ? about the severe capacity reduced , are you talking about those bad cells or other cells of the pack.
if you could share the approximate capacity left in the good cells it would help because if they are at 50 pourcent of capacity it might be to low amp hour even for my small distances. also usefull would be to have the capacity left of the cells you call severely capacity reduced.

thanks

 

[sharinginfos]

Seems like a lot of work.
When do we look at the Lego set?

If you dont know then you should charge to 100% to ensure everythings balanced, on some regular basis when you charge short, and dont drain much. Dependent on how often you ride of course, lengths of stay in the B&B Shed. Just so many bms out there, different styles and different methodology of balancing, wheres the spec sheet?

Same goes for the charger. Go slow, buy 2 dmm's if not three.

HI Calab, I am not familiar with this expression Lego set. could you tell me more about it? i dont understand what you were trying to convey.

What is B&B Shed meaning ? bed and breakfast? if you can explain more i would like to know what you say.

Sorry for my ignorance but could you link dmm because even if i assume it is a charger, i dont know wich machine your are refering to.

in the event that one cell is bad, how can i replace it with a good one? the plastic holders seems impossible to separate since they are held together by the tabs. i can solder but not spot weld.

when you say wheres the spec sheet, do you mean the specs of the cell on the picture of the Bhookup site or other specs?
thanks

 

[harrisonpatm]

They are guaranteed to work as is, and all have voltage, but we don’t know the capacity of them or the history of these packs.# not sure what it implies....

It means they might be bad. The only way to know the actual health of a cell is to charge it all the way up, and discharge it, and find out how much energy is discharged. There aren't really shortcuts. Just checking voltage tells you what voltage the cell is at, not its overall health.

First by individually tested, do you mean individually test each cell or individually test a 2p group that act like one cell?

Individual cells, not 2p group

Could you tell me what is the difference between individually tested with this charger https://www.amazon.com/WISSBLUE-Uni...ds=LifePo4+battery+charger+tester&sr=8-5&th=1

This charger will test one cell at a time (won't fit the 26650 cells you're looking at, BTW)...

and the method 4s testing with a b6? B6 seems to be able to tell the capacity of cell for each of them like if individually tested no? what is the advantage of testing them individually VS using B6 machine way? Might be important.

The B6 will test the pack as a whole. It can't tell you what individual cells are doing. At best, it can tell you what cell groups are doing, but again, that's cell groups, not individual cells.

When you say#15% of them were bad and had severely reduced capacity issues. # what do you mean by bad cell , how did you detect that ?

I broke the pack apart and tested each cell individually.

The A123 cells you're looking at individual have a new rated capacity of 2300mah. If you test the used cells and they have 2275mah, 2250mah, 2325mah, then you have good cells. If you test them and it has 1800mah of capacity, that means it has lost more than 20% of its original capacity, not great.

 

[calab]

Bikes end up in sheds and stay for long periods.
Digital Multi Meter to measure voltages, amps, to keep a close tab on the charging voltage, to dial in your top charge, to measure the amps to see if its within the spec sheet, which I know you wouldnt have, another bad joke.

Replacing a cell inside a lattice, takes a delicate touch, a dremel tool and more work. How will you reconnect the good cell? I read that soldering to tabs is easier then soldering to the can itself.

 

[sharinginfos]

Individual cells, not 2p group

This charger will test one cell at a time (won't fit the 26650 cells you're looking at, BTW)...

The B6 will test the pack as a whole. It can't tell you what individual cells are doing. At best, it can tell you what cell groups are doing, but again, that's cell groups, not individual cells.

I broke the pack apart and tested each cell individually.

The A123 cells you're looking at individual have a new rated capacity of 2300mah. If you test the used cells and they have 2275mah, 2250mah, 2325mah, then you have good cells. If you test them and it has 1800mah of capacity, that means it has lost more than 20% of its original capacity, not great.

hi first i long to discover how you achive including rectangles of part of my post and answer it outside of the box. and do it again.
it would help me to make easier posts just like you do . For now i ll do my best which is to copy paste text .

first questions checked thanks.

i read #Individual cells, not 2p group#
How can i do this individual testing? Can i use the amazon linked charger with 2 aligator wire to do that ? if yes i imagine i would have to place the aligator the closest possible to the end of individual cell. Since they are tabed in parallel, would that work or the machine would still test the duo 2p? is the only way to completely separate the cell from the module to do the test?

By saying #
The B6 will test the pack as a whole. It can't tell you what individual cells are doing. At best, it can tell you what cell groups are doing, but again, that's cell groups, not individual cells.#

are you saying that the b6 way would give results for a duo and not single cell? kind of make sense.
You seem to be saying that individual testing give more info that the b6 can give. what are those info that individual testing can give and that b6 cannot give appart for the capacity of each cell?

By saying # The A123 cells you're looking at individual have a new rated capacity of 2300mah. If you test the used cells and they have 2275mah, 2250mah, 2325mah, then you have good cells. If you test them and it has 1800mah of capacity, that means it has lost more than 20% of its original capacity, not great.#
Are you saying that the worst cells hace still 80 poucent of their capacity? does that translate as 80 pourcent of cycles left in them or we cant caculate this like that. For me 1800 mah seems like still good cell even if it reduce the global capacity of the battery pack. you juge them as bad and severly reduced capacity. i feel there is something im not understanding about what makes you say that they are bad cells severly reduced in capacity .

 

[Chalo]

you juge them as bad and severly reduced capacity. i feel there is something im not understanding about what makes you say that they are bad cells severly reduced in capacity .

They're used, possibly also old. Listing says they are all tested with good voltage which is a welcome sign, but no assurance of capacity. They're a buck and a half per cell for about 7.5 watt-hours nominal per cell. You pays your money and you takes your chances.

Lithium iron phosphate cells like that have long calendar life and long cycle life compared to what most of us use. That's one reason I suggested them to you. Another reason is they can dump tons of power at a time, which was one of your criteria. And they're really cheap, which makes the gamble a lot less of a gamble.

 

[sharinginfos]

before commiting i need to know if i will be able to test and replace a bad cell.

CAn i test each cell individually without having to dremel the tab and plastic support to take them all out?
Like if it use the charger below attaching aligator wire to the ends of the charging slot and the loose ends directly on top of the tab of a cell ,will the machine do individual testing of the cell or will it test the duo 2pcells automatically since the tab connects to the other cell in duo. ?

Any way to individually test the cells without dismembering the pack into separate cells? or what is a way that i could minimise the work in order to individually test them?

Would doing only one dremel cut of the tabs that link the cell in parallel be enough to test the cells individually?




https://www.amazon.com/WISSBLUE-Uni...ds=LifePo4+battery+charger+tester&sr=8-5&th=1

 

[sharinginfos]

The A123 cells you're looking at individual have a new rated capacity of 2300mah. If you test the used cells and they have 2275mah, 2250mah, 2325mah, then you have good cells. If you test them and it has 1800mah of capacity, that means it has lost more than 20% of its original capacity, not great.

Harrison, did you take all of the cells out of the plastic support?
Was it difficult?
would i be able to remove the plastic support only by cutting the tabs in the middle folding them up to 90 degree and pulling on the plastic holder? i hope it is possible because having to dremel the plastic support could lead to damage on the cells from the dremel...

what is this piece role? i see it would prevent the plastic holder from detaching probably . what is the consequence if i remove it?

 

[harrisonpatm]

Harrison, did you take all of the cells out of the plastic support?
Was it difficult?
would i be able to remove the plastic support only by cutting the tabs in the middle folding them up to 90 degree and pulling on the plastic holder? i hope it is possible because having to dremel the plastic support could lead to damage on the cells from the dremel...

what is this piece role? i see it would prevent the plastic holder from detaching probably . what is the consequence if i remove it?

You want to use wire snips to remove the nickel from the battery contacts. Once the nickel is gone, the plastic holders would slide right off the cells. You can then reuse the plastic holders to rebuild a pack

 

[sharinginfos]

You want to use wire snips to remove the nickel from the battery contacts. Once the nickel is gone, the plastic holders would slide right off the cells. You can then reuse the plastic holders to rebuild a pack

does that mean that there is no way to individually test the cell without cutting tab? like using magnet to place the end of the aligator clip on top the one cell 's end? that would save me work if i could do that and then only cut the nicket tab of the bad cell.

 

[harrisonpatm]

does that mean that there is no way to individually test the cell without cutting tab? like using magnet to place the end of the aligator clip on top the one cell 's end? that would save me work if i could do that and then only cut the nicket tab of the bad cell.

Nope, because they're in 2p configuration. Even if you use the alligator clip method, you'd still be testing 2 cells in parallel, because cells in parallel behave as a single cell. So yeah, if you do a discharge test that way, you could test each 2p group, looking for a result of 4600mah. But if you get a bad result, like 3000mah, it means that one of the 2p cells is bad, but you won't know which one unless you physically separate them and test them individually.

 

[sharinginfos]

ok so it would still be usefull to do this dual p test to avoid cutting tab where it is not needed. saves time i think and ill only need to cut where a duo is significantly lower.

Does this drawing represents exactly the way the cells are assembled?

what is the small tab i encircled in the post number 18? what is its role?

 

[harrisonpatm]

Your drawing is fine. I'm not sure what the tab is

 

[sharinginfos]

Your drawing is fine. I'm not sure what the tab is

ok thanks. since you have detached the cells can you tell me that is the weird tab in red circle attached to ? where does it lead?

 

[lnanek]

Maybe it was originally for the balance wires in whatever piece of electronics these used modules are pulled from.