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]

When doing indivudual testing, does the charger leaves them at 20 pourcent or 0 pourcent or 100 pourcent?
testing them all and assembling them plus installing bms plus wrapping could take me days maybe some weeks.

How long can i leave the cells at 100 without damaging them too much?

 

[eMark]

Agree, (just ignore). There is also a tab extension on a parallel bus bar at the other end of battery. Sensing tabs for BMS balance wires are sometimes soldered midway on the appropriate bus bar instead of over the cell end. That way less chance of excessive soldering heat ... possibly damaging the effective capacity of the cell. Although less likely on the cathode end.

You may have been farther ahead to get a load tester for checking the capacity of each of the 4 packs. Tthey just could be usable as is negating the possibility of checking the capacity of each of the 32 cells (8 cells x 4 packs = 32 cells).

If the voltages of all 16 of the parallel groups is within 100mV of each other i wouldn't disassemble the packs into individual cells. Perferrably use a DMM that reads to 3 decimal places (0.001 volts).

Also consider buying this capacity load tester. I don't use mine at more than a 140w load (last longer) for checking your 4-26650 A123 12v packs. BH gives the impression that those 12v A123 26650 packs are unused so hopefully all four 12v packs are useable As Is ... but still need to check the capacity (just in case). Every DIY project invariably costs more than one plans if you want to do it right with minimal frustration (or disappointment).

https://www.aliexpress.us/item/3256804832917301.html?src=google&src=google&albch=shopping&acnt=708-803-3821&slnk=&plac=&mtctp=&albbt=Google_7_shopping&albagn=888888&isSmbAutoCall=false&needSmbHouyi=false&albcp=19108282527&albag=&trgt=&crea=en3256804832917301&netw=x&device=c&albpg=&albpd=en3256804832917301&gad_source=1&gclid=EAIaIQobChMItfiOw9i3ggMV4ERHAR2iqg76EAQYAiABEgIjbfD_BwE&gclsrc=aw.ds&aff_fcid=2f371f082ad741ed86474ddd858ad48b-1699559552249-06605-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=2f371f082ad741ed86474ddd858ad48b-1699559552249-06605-UneMJZVf&terminal_id=9150f1b0d5b14534862fdb9828fc4a91&afSmartRedirect=y&gatewayAdapt=glo2usa

Amazon.com

 

[eMark]

When doing indivudual testing, does the charger leaves them at 20 pourcent or 0 pourcent or 100 pourcent?
testing them all and assembling them plus installing bms plus wrapping could take me days maybe some weeks.

How long can i leave the cells at 100 without damaging them too much?

Do capacity discharge testing of each pack (you might not need to disassemble ... https://www.amazon.com/Vastarry-Electronic-Capacity-Monitoring-Constant/dp/B0B56SP7Y9/ref=asc_df_B0B56SP7Y9/?tag=hyprod-20&linkCode=df0&hvadid=614666217538&hvpos=&hvnetw=g&hvrand=7801400781117551201&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9019693&hvtargid=pla-1728340470442&psc=1

 

[sharinginfos]

this is the volmeter i have Amazon.ca Something Went Wrong / Quelque chose s'est mal passé
is it good enough?
is it sufficient to mesure 100 millivolt ?

what is a DMM?

what would be the advantage of using the machine you linked instead of the charger linked previously below.

I understand that i may not have to dissasemble the module . i ask myself is using the charger below sufficient to establish if a duo is capacity healthy? i may have to cut a duo to establish wich cell is to replace but what is the advantage of using one of the machine you linked? i would like to understand what you are saying.

And dont they negate the possibility as you say to test the capacity of each cell? Part of me feels confused...

Sorry! Something went wrong!

 

[harrisonpatm]

You have a lot of people repeating same or similar information to you (on SecondLifeStorage as well), and you seem to demonstrate inability to retain said information, as well as not knowing a few basics about batteries and electronics that would go a long way. Try starting with some electronics basics before jumping to building an ebike pack from scratch. We don't want you to hurt yourself, which could happen at this point, with you demonstrating not knowing about how charging voltages work.

This series helped me a lot with basic concepts when I was first starting, I can recommend it. Learn to walk before you run.

 

[eMark]

this is the volmeter i have Amazon.ca Something Went Wrong / Quelque chose s'est mal passé
is it good enough?

does it read to 3 decimal places or only two when checking millivolts e.g. 3.612v of a sngle cell.or parallel group? My 9999 count DMM (DigitalMultiMeter) is helpful for me as i bottom balance the parallel groups within 5mV of each other (after resting discharge) .... before again charging my DIY battery pack. In other words i'm my own BMS as BMS balancing is very slow.

is it sufficient to mesure 100 millivolt ?

YES

what would be the advantage of using the machine you linked instead of the charger linked previously below.

Its best use is for checking discharge capacity of a battery or e.g. your 12v A123 4s2p modules (not individual cells). You had asked how long can you leave your 12v module fully charged when you may not yet have a means to discharge your 12v modues (before disassembly, if necessary).

I understand that i may not have to dissasemble the module . i ask myself is using the charger below sufficient to establish if a duo is capacity healthy? i may have to cut a duo to establish wich cell is to replace but what is the advantage of using one of the machine you linked? i would like to understand what you are saying.

By "duo" you mean the 2p parallel group. The advantage is its more professional like features (and fun) to use. However, it doesn't come with instructions and takes some time to figure out the push button functions. That said it's a handy tool for DIYers that depend on Battery Hookup for the cells used in their next DIY build.

And dont they negate the possibility as you say to test the capacity of each cell? Part of me feels confused

As a "load tester" it's purpose is check the discharge capacity of a module e.g. 4s2p or completed DIY battery build . If you have no plans to build other DIY batteries using a spot-welder and other tools, accessories then don't spend the money. Also if used at 180 watt rating it won't last long. I don't discharge over 140 watts when running discharge capacity tests.

IMO whether that WISSBLUEmodel or another popular brand they are not all that accurate, but does provide a general idea of which used/salvaged cells (modules) are still useful and which are bad. I have another popular model (same as WISSBLUE) but don't use it any more as it's to slow, only 4 cells and not as accurate as that 180w discharge load tester. Also use my RC 6s Balance Charger (set on 1s) when bottom balancing the individual parallel groups (when needed) before charging my 36v batteries to eaither 41.0v or 41.5v.

You should consider adding this book to your DIY library ... www.amazon.com/DIY-Lithium-Batteries-Build-Battery/dp/0989906701 ...

 

[sharinginfos]

HI harrisson, thanks for remembering that i have to be cautions. I have already build a propotype of vtc4 with soldering. i switch for life po4 for more safety.I think i learn well even though i sometimes want to confirm info since there are lots of variant stuff that require me to ask question and sometimes i receive satisfiying anwers, sometime reading an answer tell me to dig more into an area im less familiar with. I am learning yes. thanks for the link ill take a look at it.

 

[sharinginfos]

By "duo" you mean the 2p parallel group

As a "load tester" it's purpose is check the discharge capacity of a module e.g. 4s2p or completed DIY battery build . If you have no plans to build other DIY batteries using a spot-welder and other tools, accessories then don't spend the money. Also if used at 180 watt rating it won't last long. I don't discharge over 140 watts when running discharge capacity tests.

IMO whether that WISSBLUEmodel or another popular brand they are not all that accurate, but does provide a general idea of which used/salvaged cells (modules) are still useful and which are bad.

I intend on building one packs atm if i can get away with buying less equipment i would choose that road.

At first sight, i go along your advice of not spending the money on the load tester. I dont see reason to buy a load tester since the BH pack seems to have 1 or 2 bad cells minimum so i will anyway have to test each duo2p to see if i need to cut tab and do individual testing to isolate and replace the bad cell. To know approximately wich is the bad cell is sufficient for me .

there is a question that i need to understand to both avoid damaging the cell and choosing the right charger for individual testing it goes like this. can i leave those cells fully charge for couple of days or weeks without damaging them? Because i read that they dont like to be fully charged for long time. taking the time pressure off would be nice if it is relevant in regard to avoid damaging the cells waiting to be used.

Correct me if im wrong here is the way i see it. 2 choices A and B Maybe there is stuff i dont see in the equation. If leaving the cells fully charged is not a problem unless for months, i can use the wissblue charger.
A) I would test the capacity of cells and charge them to full and leave them like that until placing bms since the charger does not seem to allow me to discharge them to less than 3.65v. it seems I either leave them full 100% or empty wich since it did find the manual online i guess is 20%.

B)If leaving cells fully charged can damage them then it would be better to bring them to a voltage lower than 3.65 once the capacity test is done. In this case i imagine that i should buy an iMAX B6 and use it at 1s with everycell(yes one by one). i would do a capacity test on them and from the youtube video i have seen, this charger allows us to discharge a cell and then manually select the voltage that we want to bring a cell to(less than full 3.65v) that way it would not damage the cells if i leave them like that while capacity testing the other cells and preparing BMS installation and assembly.

I dont know to what voltage i would bring them back to though and if the selected voltage is important before i install the bms.

Which charger would you suggest me to use knowing that the cells would have to wait before being assembled and used in a complete pack?

 

[sharinginfos]

Any reason to choose one over the other?

 

[docw009]

These are used cells, so I wouldn't worry about the 100% storage. For all you know, they are 100% right now, These are also LiFePO4 cells with a flat charge curve. You can't easily tell 80% from 90% by looking at the voltage.

An Imax B6 is a handy charger, and it would give you a lot of info about each module. If you hook it up in single cell mode, and connect to a single cell pair, you could get the capacity of each cell, though that is not its main function. I use mine to (a) charge to 100% (b) discharge to storage voltage. It will also take them down to discharge level, but for Li-Ion, it stops at 2.8V, not 2.5V. To use as a balance charger, you will have to buy the connectors and make a balance harness for each module.

That's getting too far ahead. If you already have the modules, take your meter and measure each cell pair directly, putting the probes on the opposite terminals. Four measurements per module. You'll probably find them all close to each other, and sitting near 3.6V.

I believe you're running an ebike, since you mentioned going up a hill. The A123 is a 2.3AH cell when new. Each module is about 4AH then, If you do four modules, that's a very modest 16S-2P battery. I have worked with 4AH batteries. Lot of voltage sag on mine. While the A123 is a robust cell, I don't know about this application for the bigger ebike motors. I'd use 8 modules. With less stress on the cells, they will stay in balance longer.

I would also suggest an appropriate LiFePO4 16S BMS and a 16S LiFE charger. LiFEPO4 holds a constant voltage til it's near discharge, and then the voltage falls fast. This would be hard to monitor using a voltage monitor on a bike w/o a BMS. A BMS with one charger is also more convenient. If you used the IMAX, you would have to hook it up four times. I believe 16S balance chargers would be pretty expensive too. I don't think a Satiator is needed either. A LiFePO4 charger with a fan is not expensive.

 

[eMark]

there is a question that i need to understand to both avoid damaging the cell and choosing the right charger for individual testing it goes like this. can i leave those cells fully charge for couple of days or weeks without damaging them? Because i read that they dont like to be fully charged for long time. taking the time pressure off would be nice if it is relevant in regard to avoid damaging the cells waiting to be used.

There is no purpose in leaving a cell fully charged after initial capacity testing ... Amazon.com ... size of resistor/load depends on how fast you want to discharge a cell (e.g. 250 W). It helps to have another inexpensive tool besides your WISSBLUE capacity tester to play around with to speed up one's all around learning curve.

Correct me if im wrong here is the way i see it. 2 choices A and B Maybe there is stuff i dont see in the equation. If leaving the cells fully charged is not a problem unless for months, i can use the wissblue charger.
A) I would test the capacity of cells and charge them to full and leave them like that until placing bms since the charger does not seem to allow me to discharge them to less than 3.65v. it seems I either leave them full 100% or empty wich since it did find the manual online i guess is 20%.

Are you discharging your 4s2p modules to 8.0v or 8.8v before doing your capacity testing while charging to 3.60v per duo or 14.4v. Check resting voltage after 15 min and again after 1 hr.

B)If leaving cells fully charged can damage them then it would be better to bring them to a voltage lower than 3.65 once the capacity test is done. In this case i imagine that i should buy an iMAX B6 and use it at 1s with everycell(yes one by one). i would do a capacity test on them and from the youtube video i have seen, this charger allows us to discharge a cell and then manually select the voltage that we want to bring a cell to(less than full 3.65v) that way it would not damage the cells if i leave them like that while capacity testing the other cells and preparing BMS installation and assembly.

I dont know to what voltage i would bring them back to though and if the selected voltage is important before i install the bms.

Suggest no higher than 3.1v to 3.2v (49.6v to 51.2 nominal voltage for your 48v DIY pack) when attaching the BMS sensing wires.

Which charger would you suggest me to use knowing that the cells would have to wait before being assembled and used in a complete pack

After test charging modules as suggested above and aok so far shat about this 48V charger ...
www.amazon.com/WAOUKS-LiFePO4-Battery-Charger-Auto-Stop/dp/B07G32Q2W8/ref=sr_1_8?crid=35WZ3AWKQU37R&keywords=48V+%2F+58.4V+3A+Lithium+Lifepo4+Charger+110V+120V+for+48V+Lifepo4+Battery+with+Cooling+Fan+Multiple+Protection+Functions&qid=1699720426&s=electronics&sprefix=48v+%2F+58.4v+3a+lithium+lifepo4+charger+110v+120v+for+48v+lifepo4+battery+with+cooling+fan+multiple+protection+functions%2Celectronics%2C239&sr=1-8
The resting voltage after charging your 16s2p (preferrably 4p) DIY A123 26650 DIY BH battery should be close to 57.6v (if new cells).

Hopefully the BH 4s2p modules turnout to be useful for your intended application with a trustworthy extended life

 

[sharinginfos]

These are used cells, so I wouldn't worry about the 100% storage. For all you know, they are 100% right now, These are also LiFePO4 cells with a flat charge curve. You can't easily tell 80% from 90% by looking at the voltage.

An Imax B6 is a handy charger, and it would give you a lot of info about each module. If you hook it up in single cell mode, and connect to a single cell pair, you could get the capacity of each cell, though that is not its main function. I use mine to (a) charge to 100% (b) discharge to storage voltage. It will also take them down to discharge level, but for Li-Ion, it stops at 2.8V, not 2.5V. To use as a balance charger, you will have to buy the connectors and make a balance harness for each module.



, that's a very modest 16S-2P battery. I have worked with 4AH batteries. Lot of voltage sag on mine. While the A123 is a robust cell, I don't know about this application for the bigger ebike motors. I'd use 8 modules. With less stress on the cells, they will stay in balance longer.

I would also suggest an appropriate LiFePO4 16S BMS and a 16S LiFE charger. LiFEPO4 holds a constant voltage til it's near discharge, and then the voltage falls fast. This would be hard to monitor using a voltage monitor on a bike w/o a BMS. A BMS with one charger is also more convenient. If you used the IMAX, you would have to hook it up four times. I believe 16S balance chargers would be pretty expensive too. I don't think a Satiator is needed either. A LiFePO4 charger with a fan is not expensive.

I intend to only use the b6 charger to test capacity and charge it back to a voltage that does not damage the cell that will have to wait before bein assembled . Once assembled i would use a 16s charger lifepo4 it will be more simple.
i have not found a 48v balance charger affordable for life po4 but since i will use a bms(one that allow balancing even at 80pourcent) , i understood that a regular charger 48v would be a good combo with the bms once the pack is assembled. Or maybe you know a 48v lifepo4 affortable balance charger?

yes 4ah is little but i want a light battery so that is why i am talking about building a 2p16s battery.
I plan to rder modules soon . i just want to know the material needed to balance the cell and test capacity so that i dont have a costly surprise of having to buy expesive gear to do so. and also have advice about stuff i might not be aware like voltage sag that you are pointing out.

In electricalworkbook, i read# Voltage sag refers to voltage dips typically for 0.5 to 30 cycles# Does voltage sag means the voltage goes down quicker than expected for a given battery or does it mean something about the cycles lifespan of the battery.
Like concreatly what is the@ beaware@ you are trying to convey me about expectations of the battery future behaviour.

Of course i expect the voltage of a 2p16s battery to go down quicker than if it was a 4p16s, it is normal. voltage is a reflection of energy left . but what you might be saying is that it goes even quicker or other unusual behavior of the battery? not sure what you meant.

by looking the graphic below, i put the hypothesis that for some reason a voltage sag is an event when the battery does not work as intended for a limited amount of time and than comes back to its normal personality. how would that translate in real world?

 

[sharinginfos]

There is no purpose in leaving a cell fully charged after initial capacity testing ... Amazon.com ... size of resistor/load depends on how fast you want to discharge a cell (e.g. 250 W). It helps to have another inexpensive tool besides your WISSBLUE capacity tester to play around with to speed up one's all around learning curve.

Are you discharging your 4s2p modules

Suggest no higher than 3.1v to 3.2v (49.6v to 51.2 nominal voltage for your 48v DIY pack) when attaching the BMS sensing wires.

Hi
Unless there is a good reason to discharge or test the full modules, i dont intend to do that since I will test the 2p individually and the individual cell of a 2p duo that would be lowerAmphours and replace the bad cell. These modules will probably have at least one bad cell from what I understand so I dont see the point of testing the modules themselves. is my line of thought correct?

Can you confirm that the b6 can allow me to 1s charge the cells to 3.1v after having tested the capacity? in videos it seems like it but having a confirmation would be nice. Wich capacity charger would you suggest me to buy ? the b6maz or the wiseblue. I would go for the b6 at first glance since it seems like it can allow me to charge to 3.1v and the wiseblue does not.

When adding the bms at this 3.1v voltage for every cell, would that be a #middle balancing strategy#? usually i see top or bottom balancing strategies. How would middle balancing turn out in the long run? Maybe it did not capture my attention but why isnt there more people talking about balancing a pack at 3.1. maybe it has to do with the graphic line of lifepo4 voltage flat curve in the middle part of the graphic. would my cells be balanced good enough? Please tell me more about it.

About the amazon 10 dollar device, i understand that you suggest that i plug that in, in order to have a second opinion about the capacity test and also get the resistance reading.Right? do you know if there is a tutorial about how to use this godsent device? It would be for 1S individual testing right?

 

[sharinginfos]

I commited!
ibought 6 modules. before the ship it i have a small window of time to add stuff from their site.

what could be usefull from their site for my battery apart from the clipper flush cutter?
I already have a multimeter and the soldering iron belowweller w100p.
My reading told me that i want a bms with several features one important among them is the ability to set the balance capability at lower voltage than full, like maybe 80 or 75. i dont know if their bms can do that by reading the descriptions.

any other stuff that would be good to buy while i am at it ? Icould also add modules depending on the answer about the voltage sag thing

thanks

 

[calab]

I intend to only use the b6 charger to test capacity and

It takes forever, but it does read something when it charges doesnt it, either way I doubt it will be very accurate measurement for capacity. When I had the official one and the knock off one, both blew smoke not sure why, I never could tell if the readout was the same as the battery capacity new anyways, harder to tell when its older.

 

[sharinginfos]

It takes forever, but it does read something when it charges doesnt it

hi can you express this with other words? i dont understand what you are trying to convey.
And how long would it take to capacity test one cell approx?

 

[calab]

Its been so long since I used those B6 chargers. The balancing feature from what I remember has such a low amperage rating that it takes a very long time for it to balance a pack, and when the voltages are way off it takes even longer. I was dealing with 5 and 6s lipo's (playing Lego with Lipo bricks.) for 12s packs ebiking. The accuracy of a cheap item such as the B6, isnt very accurate and capacity is tricky to properly measure from what I gather. To capacity test one cell, wouldnt take as long as a pack, dependent on its wh of course, the more wh the longer it will take so one cell wouldnt take long for capacity check but its not accurate. Might get you in the ball park. I'd trust a charger named the iCharger to do a capacity test, they run ya $200+

- For one cell you could make your own discharge device, an old toaster works well for 1 cell. Alligator clips on both ends, a dmm to measure current, another dmm to measure voltage, a note pad, a pen. maybe a fan to help dissipate the smoke coming off the toaster wires at various lengths dependent on the amperage you want to pull. The less amps, the more toaster wire you use.

 

[sharinginfos]

hum anyone would happen to know how to answer the post #37 i made following docw009 's sharing #35?

 

[eMark]

Hi
Unless there is a good reason to discharge or test the full modules, i dont intend to do that since I will test the 2p individually and the individual cell of a 2p duo that would be lowerAmphours and replace the bad cell. These modules will probably have at least one bad cell from what I understand so I dont see the point of testing the modules themselves. is my line of thought correct?

Yes ... assumidng there is at least one inferior cell in one of the 4 "duos" of each of your 4 4s2p modules.

Can you confirm that the b6 can allow me to 1s charge the cells to 3.1v after having tested the capacity? in videos it seems like it but having a confirmation would be nice. Wich capacity charger would you suggest me to buy ? the b6maz or the wiseblue.

It should charge at only 1s, but you'll need to make up your own 1s outut patch cable as you don't need to use that 2s-6s balancer plug-in. The 6s RC Lipo/Lion/LiFeP04 Charger i use is ... www.amazon.com/HTRC-Charger-Balance-Discharger-Batteries/dp/B0894DHCDK/ref=asc_df_B0894DHCDK/?tag=hyprod-20&linkCode=df0&hvadid=459723993320&hvpos=&hvnetw=g&hvrand=2019620902604196296&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9019693&hvtargid=pla-945168934471&psc=1

I would go for the b6 at first glance since it seems like it can allow me to "charge to 3.1v" and the wiseblue does not.

Didn't you mean to also say "discharge to 3.1v" using the WISEBLUE? Why do you need to charge to only 3.1v instead of 3.65v when doing a capacity test via 'charging' as opposed as doing a capacity test via 'discharging' ? Mosgt capacity testing is via discharging to simulate the discharge capacity while ebiking.

When adding the bms at this 3.1v voltage for every cell, would that be a #middle balancing strategy?

An active equalizing balance board will balance at bottom, middle or top when the voltage variance of all the p-groups is more than 100mV and will stop balancing when variance is no more than 100mV

Would take too long to explain pros and cons of different types of balancing. The vast majority of BMSs top balance using resistance discharge.. The whole idea is to balance the parallel groups [hopefully] within at least 25mV variance of each other whether via top, middle or bottom.

With your 4s modules no greater variance than 100mV should be possible with your used 4s 2p modules. Hopefully after discharge all 2p4s modules will be within 100mV of each other assuming you have manually bottom balanced all four 2p 'duos' within 25mV of each other before charging or top balancing within 25mV of each other before discharging.
Because most 1865/2170 commercial battery [inexpensive] BMSs use resistance discharge balancing which doesn't begin until the battery is nearing a full charge (say 4.10v). Some less expensive 1865/2170 Chinese batteries only use a BMS for over and under voltage protection (without any balancing feature for the p groups). Which should suffice assuming all the cells are A grade and the owner doesn't abuse the battery with too much continuous maximum discharge (like a prolonged hill climb at full throttle) with little pedal power assistance.

About the amazon 10 dollar device, i understand that you suggest that i plug that in, in order to have a second opinion about the capacity test and also get the resistance reading.Right? do you know if there is a tutorial about how to use this godsent device? It would be for 1S individual testing right?

Right (each.2p duo). Also should have said 25w not 250w for resistance discharge testing. Use a 12v auto taillight bulb. I'm going to order a couple to check out (in case one is returned if faulty or keep as a spare) ... www.amazon.com/Digital-Lithium-Battery-Capacity-Resistance/dp/B0981DHDJG

NOTE: Just went back (correcting typos) and hopefully further clarification.

 

[eMark]

Hopefully it will work when only discharging a fully charged 2p duo at 4.15-4.20 volts to 3.10 or 3.00 volts. Anyway will find out if its worth the price. It sounds just like what you could put to good use.

It shouldn't be difficult for you to figure out how to use it (unlike the ATorch Load Tester).

 

[sharinginfos]

Didn't you mean to also say "discharge to 3.1v" using the WISEBLUE? Why do you need to charge to only 3.1v instead of 3.65v when doing a capacity test via 'charging' as opposed as doing a capacity test via 'discharging' ? Mosgt capacity testing is via discharging to simulate the discharge capacity while ebiking.



With your 4s modules no greater variance than 100mV should be possible with your used 4s 2p modules. Hopefully after discharge all 2p4s modules will be within 100mV of each other assuming you have manually bottom balanced all four 2p 'duos' within 25mV of each other before charging or top balancing within 25mV of each other before discharging.

Because most 1865/2170 commercial battery [inexpensive] BMSs use resistance discharge balancing which doesn't begin until the battery is nearing a full charge (say 4.10v). Some less expensive 1865/2170 Chinese batteries only use a BMS for over and under voltage protection (without any balancing feature for the p groups). Which should suffice assuming all the cells are A grade and the owner doesn't abuse the battery with too much continuous maximum discharge (like a prolonged hill climb at full throttle) with little pedal power assistance.

Right (each.2p duo). Also should have said 25w not 250w for resistance discharge testing. Use a 12v auto taillight bulb. I'm going to order a couple to check out (in case one is returned if faulty or keep as a spare) ... www.amazon.com/Digital-Lithium-Battery-Capacity-Resistance/dp/B0981DHDJG

NOTE: Just went back (correcting typos) and hopefully further clarification.

from what i understand the wiseblue cannot stop at 3.1v but b6 can. my plan is to do capacity test (i dont know yet how to do it but ill learn it when time comes) i do beleive if it is your questions that the capacity test is done with 3.65v yes . Is the capacity test done when charging or discharging i do not know yet.
But i aim at: after having done the capacity test , the b6 can bring the cells to 3.1v. can you confirm me itcan do that possible?

when reading your paragraph :

@An active equalizing balance board will balance at bottom, middle or top when the voltage variance of all the p-groups is more than 100mV and will stop balancing when variance is no more than 100mV.@
a question comes to my mind and it is . when all the cells will have been brought to 3.1v with the b6 charger, can i install the bms wire at that moment or do i need to do an additionnal step of using a active balance board that would make sure that they are to even voltage. maybe that is what you are advicing me to do , im not sure , i have never used an active balance board.
can we set the active balance board to a specific voltage or it chooses the voltage by him self.?
If it chooses the voltage by itself, how many cells can it handle at one time? 16s and 2 cell in p so 32 cells tolat? do you have a link of a active equalizing balance board affordable that would do the job.

is the active equalizing balance board only necessary for the situation where i would balance them at 3.1v(flat curve) or is it also necessary to use a active equalizing balance board if i balance the cell at 3.65v (not a flat curve)?

Could you tell me more about the reasons why to advice me to balance it at 3.1v ? You talked about the bms wire but iwould like to understand the why and if there are other reasons.

how do i what you talk about in this paragraph?
#With your 4s modules no greater variance than 100mV should be possible with your used 4s 2p modules. Hopefully after discharge all 2p4s modules will be within 100mV of each other assuming you have manually bottom balanced all four 2p 'duos' within 25mV of each other before charging or top balancing within 25mV of each other before discharging.# you talk about a bottom balance but i thought you said to balance at 3.1v.. i feel confused .

i do intend to buy a bms made for lifepo4 and that has the ability to start balancing a a voltage i can set up (so that it stills ballance even if i dont do full charge.

why would i need to make a discharge device like using a toaster or light bulb? idont understand why you bring this idea. could you clarify?

ps you wrote 4.15-4.20 volts to 3.10 or 3.00 volts but the cells are not li ion regular, they are lifepo4.

by the way when you use the expression#active equalizing balance board# do you mean a active balancer or is it a different device. I dont know yet if i will add a active balancer once the battery is assembled in the battery since people told me it drains the battery. maybe that once the battery is assembled the bms balancing capacity will be sufficient? i dont have enough xp to judge on that . Also i seems that having a active balancer could leave me unaware of some problems that could emerge further down the road like if after x cycles a cell becomes bad.
thanks

 

[eMark]

My mistake ... should have said 3.60v to 2.50v ... when discharging for capacity test. I prefer discharge test as representative of ebike Ah discharge. Apologize for lengthy reply apparently more confusing than helpful?.

@An active equalizing balance board will balance at bottom, middle or top when the voltage variance of all the p-groups is more than 100mV and will stop balancing when variance is no more than 100mV

With your used A123 cells you might find that keeping the variances of all 16 2p-groups balanced within 100mV of each other is close enuf. Thus the reason why some also choose to use a "balance board" ... www.ebay.com/itm/196044328306?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A1IPAOt0FjQOKsGuHXtNllLQ47&norover=1&mkevt=1&mkrid=711-166974-028196-7&mkcid=2&mkscid=101&itemid=196044328306&targetid=2237966555984&device=c&mktype=pla&googleloc=9019693&poi=&campaignid=20742243316&mkgroupid=155572720015&rlsatarget=pla-2237966555984&abcId=9330183&merchantid=425221196&gclid=EAIaIQobChMIvJCI7_rIggMVO1N_AB0UagacEAQYAiABEgJ4P_D_BwE ... as 100mV is the best most balance boards can achieve.

Could you tell me more about the reasons why to advice me to balance it at 3.1v ? You talked about the bms wire but iwould like to understand the why and if there are other reasons.

Because you had asked me -why not middle balancing (3.1V).

Every DIYer has there own preferred methods. I don't trust most BMSs and don't need to buy an expensive so-called "smart" BMS. My etriking use is casual (easy-going) so never FULL Throttle shortening the life or abusing my four batteries (2 DIY wo/BMS and 2 commercial) w/BMS). I like to experiment so try different methods (my KeepItSimple approach is "less is more")

My impression is that you already know enuf to go ahead and fabricate your 2p16s battery (as best as possible), and then learn as you go. That's how all DIYers begin and continue their ebiking journey using cells from BH.

 

[sharinginfos]

With your used A123 cells you might find that keeping the variances of all 16 2p-groups balanced within 100mV of each other is close enuf. Thus the reason why some also choose to use a "balance board" ... www.ebay.com/itm/196044328306?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A1IPAOt0FjQOKsGuHXtNllLQ47&norover=1&mkevt=1&mkrid=711-166974-028196-7&mkcid=2&mkscid=101&itemid=196044328306&targetid=2237966555984&device=c&mktype=pla&googleloc=9019693&poi=&campaignid=20742243316&mkgroupid=155572720015&rlsatarget=pla-2237966555984&abcId=9330183&merchantid=425221196&gclid=EAIaIQobChMIvJCI7_rIggMVO1N_AB0UagacEAQYAiABEgJ4P_D_BwE ... as 100mV is the best most balance boards can achieve.

Because you had asked me -why not middle balancing (3.1V).

Every DIYer has there own preferred methods. I don't trust most BMSs and don't need to buy an expensive so-called "smart" BMS. My etriking use is casual (easy-going) so never FULL Throttle shortening the life or abusing my four batteries (2 DIY wo/BMS and 2 commercial) w/BMS). I like to experiment so try different methods (my KeepItSimple approach is "less is more")

My impression is that you already know enuf to go ahead and fabricate your 2p16s battery (as best as possible), and then learn as you go. That's how all DIYers begin and continue their ebiking journey using cells from BH.

 

[sharinginfos]

Hi so with those used cell do you advise me to use an active balance board ? to do the initial balancing or for further on?
Maybe i could start without and see how it goes?

still not sure why we talk about 3.1v hahaha. One ES memeber said that keeping those cells full 3.65 v for long time is not harmfull to them , do you agree? because the reality is that i will move from steps to steps having to order and wait for orders and then take time when i am available to assemble wich can end up in the end with cells having to wait for some months before being able to be used in an ebike.

what is your personnal deinition of "smart" BMS?

 

[sharinginfos]

is it ok to bump ?