Any advantages to going with two 6s VS three 4s VS four 3s?

[omegagamer89]

Im considering buying 12 of the Turnigy 1s 5000mAh 20C lipo cells, and making a new 12s battery pack. I already have a pretty good idea of how Im going to do everything and wire it all up and all that, but I have a question;

Is there any advantage (in terms of charging, balancing, performance, cell life, output, drain, etc) to setting these 12 cells up into, say, three 4s packs, versus two 6s packs?

Im going to be using an ECO6-10 200W 6s charger if that matters. Obviously in that case, doing two 6s packs would allow for easier charging (only 2 packs to charge vs 3 or 4 or more) but is there going to be any advantage in terms of cell life, balancing, performance, etc?

Im guessing that one 4s pack would charge faster than one 6s pack, but would either arrangement charge "Better?"
In other words, would the 4s pack (or 3s, or 2s, etc) keep the balance between cells better? Would either arrangement be more likely to get out of balance or have issues than the other?

Are there any other advantages/disadvantages to going with two 6s packs, as opposed to three 4s, as opposed to four 3s, as opposed to six 2, as opposed to twelve 1s?

Thanks in advance for the help. ^_^

 

[friendly1uk]

First up, do you know that charging with toy chargers is not the preferred method for manufacturers. In fact, non would do it how your intending. It is inherently dangerous. You should seriously consider building an EV pack like the professionals. $100 will put everything on your doorstep to charge your pack in 90 minutes, with the complexity of charging your phone. Just one simple wire.

If you must use the toy stuff, there is no real difference in any configuration you talk of. Just that a couple of 6s packs could charge together in parallel.


I feel bad now... I have advised a method using RC gear. I have seen other forum members do the same, and then watched the OP's house burn down. I really don't want any part in your RC charging methods. But if your going to go that route, keep it simple as you can and put 6s packs with your 6s charger. Then the very first time you get the wires wrong, admit it was a bad idea, bin the lot and buy the $100 electric vehicle charging kit you should really be looking at now.

 

[Punx0r]

Do you sell this stuff?

Omegagamer, the 200W rating on the charger means that as the battery voltage is increased the current it can charge at is reduced. Say, it will do 20A at 10V, at 20V it can only deliver 10A. You'll likely find charging time doesn't matter how you configure the cells.

If you have 12x 3.7V 5Ah cells you have 12x3.7x5 = 222 watt-hours. On a 200W charger that will theoretically take a little over an hour no matter how you look at it. In reality it would take a little longer as the charger gradually tapers off the current at the end of the charge.

 

[omegagamer89]

First up, do you know that charging with toy chargers is not the preferred method for manufacturers. In fact, non would do it how your intending. It is inherently dangerous. You should seriously consider building an EV pack like the professionals. $100 will put everything on your doorstep to charge your pack in 90 minutes, with the complexity of charging your phone. Just one simple wire.

If you must use the toy stuff, there is no real difference in any configuration you talk of. Just that a couple of 6s packs could charge together in parallel.


I feel bad now... I have advised a method using RC gear. I have seen other forum members do the same, and then watched the OP's house burn down. I really don't want any part in your RC charging methods. But if your going to go that route, keep it simple as you can and put 6s packs with your 6s charger. Then the very first time you get the wires wrong, admit it was a bad idea, bin the lot and buy the $100 electric vehicle charging kit you should really be looking at now.

Why do you say I shouldnt use the 'toy' charger I mentioned? Im not arguing, Im just asking what, specifically, you feel makes it a bad choice. As far as I can see, it should work fine. Its designed and built to charge lipo batteries, its monitors each cell, balances, tapers the amount of charge, etc. So then, why do you feel its a bad choice?

Also, if you wouldnt use the ECO6-10, then what would you recommend? Could you please provide a couple links to products you would suggest?

Do you sell this stuff?

Omegagamer, the 200W rating on the charger means that as the battery voltage is increased the current it can charge at is reduced. Say, it will do 20A at 10V, at 20V it can only deliver 10A. You'll likely find charging time doesn't matter how you configure the cells.

If you have 12x 3.7V 5Ah cells you have 12x3.7x5 = 222 watt-hours. On a 200W charger that will theoretically take a little over an hour no matter how you look at it. In reality it would take a little longer as the charger gradually tapers off the current at the end of the charge.

Uhhh... no? I dont sell these. Not sure what you mean.

I know that 200W is 200W, and that higher voltage means lower amperage, and vice versa because it can only total 200W max, so thats not what Im worried about. An hour or so charging time is fine with me. With my current setup, it takes about an hour and a half, per pack, and I have 3 packs and only one charger. (Other charger broke, and IM waiting on a parallel charging harness to ship)
But for this new pack, an hour charging time if ok. Obviously faster is better, but anything under an hour and a half or so for the whole pack is acceptable.

The charging part itself Im good with; like, I know how the charging itself will work. I just wanted to know if there was any advantages in terms of overall battery life, or if maybe one arrangement would be harder on the cells than another. I know that two 6s packs will make for more convenient charging, but I dont know if, for example, three 4s packs will last for 18 months, and two 6s packs will only last for 14 months, or if two 6s packs will tend to heat up more during use than three 6s packs, etc.

 

[dogman dan]

Friendlyuk is on a mission, but he is not wrong. However, a bms will not make crappy cells that like to flame safe.

They can still burn your house down, the difference is only that it happens if a bms fails, rather than you fail.

So continue to charge and store this cheap RC battery in a place you'd build a fire.

Now that the public service warning has been given, 6s 4s or 3s. I have all three. The 3s make a pack with the most wire hanging out of it, followed by the 4s, then the 5s. A 12s pack made from 4- 6s packs will be the neatest. Less connectors means the pack takes up less space. But for some reason, the 4s stuff tends to be the cheapest per watt hour. So if price is the only thing, 4s may still be the best deal.

I have the 6s because my mower runs on 6 or 7 s. I have some 4s because it was cheap, it takes up more space, but only because it's hard packs rather than soft. The 3s was bought last year, because by may last year everything was out of stock. This year I bought my summer supply early.

I have never heard anybody claim one type of pack lasted longer than another. But do remember this is cheap junk cells. At any time, a batch can turn out to be total crap. So pick wrong out of pure bad luck, and all will suck. And we know if that happens, you can forget a quick easy refund. I will not order more than $200 of this junk at a time.

For sure, you can't get what is out of stock. If it's not in the US warehouse, I'm not buying it.

 

[omegagamer89]

It seems everyone agrees that these types of cells are crappy, but I dont understand why. What is it about these that makes them bad?
Right now I have three of the Turnigy 4s 5000mAh 20C hard case batteries that I run on my bike, and they have never given me any problems at all. The only reason Im even making a new pack is because I want something with more Amp hours so I can ride for longer without having to stop and charge.

Why are these batteries bad?

What batteries would you suggest instead? What do you personally use? (links would be greatly appreciated. ^_^ )

 

[dogman dan]

Lico is the most prone to burn your house down chemistry there is. They can be made safe, you carry lico in your pocket all day in your cell phone, or it's in your pad or laptop.

But these RC cells are not made to that level of quality. Contaminants like a speck of humidity make em puff easy, or they may have other contaminants. Then they are likely to fail completely, puff, have high resistance, or they have even been documented to melt their case just sitting on a shelf never used. Damage in shipping may have been the culprit in that particular case. Even hard shell packs should never be dropped. Of course, in shipping they fall from one conveyor to another repeatedly at the sorting centers. So they can easily arrive with some physical damage, including leaking.

You got em cheap, because they were made cheap. But typically at least 90% of any given bunch of cells will be good cells, with decent c rates, and little risk of fire unless you break the lipo rules. The key thing is fully understanding that you need to sort the cells.

I just keep trying to make the point that no bms will protect a damaged cell. So even if you use a bms, you still have to do a testing and sorting procedure with these cheaply made cells. The truth is, they are TOY batteries like UK says, not proper EV stuff. That's why no E bike shop with any sense will sell you them.

 

[omegagamer89]

Ok then, if these are cheaply made toy cells, then what are some GOOD cells that YOU would use? I dont mean to be rude, but I have kinda asked that question 3 times already and everyone has ignored it.

I mean, its great that you want people to use good quality stuff. Thats awesome, way to do a good deed. But you dont just tell them what NOT to use, thats not how it works. If you want to actually HELP anyone, you have to provide them with an alternative.

You say, "Hey, use this rather than using this, for these reasons."

You cant just say "Dont ever use these, use something else, but Im not gonna say WHAT else." and leave it at that.

So, i respectfully ask once again; If you would not use these what ----WOULD---- you use?

 

[dogman dan]

Beats me. My budget only stretches to more cheap toy RC lico, and of the cheapest 20c type at that. I just bought more, and have 25 ah of it in 14s configuration.

My first batch, after sorting out the 3 packs that were doa, and the two that died early, still run today 4 years later. Down to 50% capacity now, but once you get rid of contaminated packs, they are reliable. I had 3 bad packs out of 24, and the other two I believe I killed with harsh use.

I sort the obviously defective ones out as soon as I can, and then continue to watch them pretty close every cycle. I NEVER trust them like I trusted my Ping lifepo4 packs.

I charge the scary way, no bms, on a bulk lithium charger. But I do that in my fireplace. I do not leave this stuff on my bike, in the garage ever. I bring it to the storage, that is in the fireplace, or in an old refrigerator outside.

If I'd had unlimited funds, then I would have at least one Cellman 20 ah A123 pouch pack. Or some of the cells Dr Bass periodically sells, or a Cellman triangle pack. Size of lifepo4 wouldn't matter much to me on my cargo bike. But the trail bike would be real likely to still be running lico, for the high amps it can deliver.

If you have money, I'd say go straight to cellman if you run only 20-30 amps. But if you run a hot rod, or just a strong bike like my cargo bike, then you need something able to handle 10c, 20c, or more.

These "toy" cells remain the only thing I know, that will run a 40 amps controller on just 5 ah of it, if you get 40c or better stuff. But lots of good limn varieties are out there if you are not hot rodding. It's small and light, but not 20c.

Just don't put the RC toy stuff on a wooden table, next to the curtains, and charge them. Don't ding them either, make a good box for the soft packs.

 

[Punx0r]

RC lipo

* cycle new packs and check for defective cells
* protect from mechanical damage (impact, chafing)
* discharge conservatively
* Check cell voltages before charging to ensure one hasn't gone dangerously low
* Charge with high-voltage monitoring on each cell (i.e. use the balance connector, don't bulk charge)
* As dogman says, charge in an area where if a pack were to flame out, it won't cause a fire
* Don't leave them charging unattended (unless in a fireproof area, like outdoors)

Pretty much how you should treat any battery, but bearing in mind that RC lipo can be more temperamental than most.

Cells that are mechanically damaged or over-charged or over-discharged are the ones that can go up in flames. Observing voltage limits of 3.6-4.1V per cell (as opposed to 3.0-4.2) will not only greatly extend their cycle life, but will help avoid this. You will lose 10-20% capacity doing this.

Whether your battery management system is an RC balance charge, a BMS board attached to the pack, or yourself with voltage monitors or alarms, it's all the same. Just ensure whichever you do, it is effective. RC lipo isn't for the clueless, the forgetful, the careless, or those with no technical ability.

 

[friendly1uk]

Quite a bit to steer through here.
LiPo is as powerful as it comes, so can cause the most destruction. It is not made with safety as it's number one priority. lifepo4 is the safer version. Question is, just how unsafe is it?

From reading here, or any other forum, you can see nearly all the fires involving lipo batteries are not due to the chemistry. There is a case where a pack got squished and burnt, but in 90% of cases the user made a charging mistake. They used Radio Control charging stuff which meant swapping wires about, and most simply got complacent and started a fire. We all like to think we get it right every time, but the evidence plays out differently.

Years ago RC chargers didn't balance. Fires were common, and the answer was charge where fires don't matter (still good advice now). As time passed, balance chargers came along for them. Still quite rough and ready but the common cause of fires was removed by adding balancing. However it is still only safe enough for playing with in controlled environments, and offers no means of pack protection apart from while charging. Electric vehicles and banks of batteries within buildings deserved further protection. So the Battery Management System (bms) came about.

A bms consists of two parts. You have a power supply that lives at home, just like with the RC charging gear. The balancing circuitry lives on the bike full time though. Having circuitry on the bike opens the door to full time monitoring. One of the reasons for fire is over discharge. Over discharge often leads to packs failing prematurely too. A bms stops this by switching off the pack once no more charge is available. Another fire cause is short circuits, which can also be controlled by the bms. Another is chargers floating off to an incorrect voltage, which the bms will also stop as it has it's own protection, as well as the bit at home being protected. Thus halving that risk. The bms approach was developed for these extra layers of protection and also for simplicity. All you have to do is plug your box at home to the bike with a simple power cord and that is all. Many RC charging fires are avoided by simply not having to swap wires about or program the charger each time. All them little balance wires the RC charger wants moving about are not designed for moving about, they are weak 'one shot' plugs with nothing to get hold of and no mechanical clamping of the wires. In time this RC charging practice also leads to dangerous faults as wires come loose.

The RC approach really is unsuitable. This is why a better system was developed. As using a bms is the normal route for an ev manufacturer it is produced in great numbers. Making this more complete technology actually cheaper than the RC stuff.

RC stuff really is just wrong. If is very easy for a 10yo to explain it to you, so the word will go around amongst newbies for many years to come. Perpetuated by RC groups who need no better, and there manufacturers who will happily sell you another $1000 chopper when yours burns. Offering protection in the form of low voltage alarms that you simply can't hear, and that is about it because a 30gram circuit board is not desirable for weight conscious builders who have never actually heard of a bms anyway.

Many industries use lipo batteries. We have ev's that all use a bms. We have battery backup situations that all use a bms. We have mobile devices such as computers and phones, they all use a bms. In fact everybody uses a bms except for modelers.
When I got here, some users of the forum did have reasons they genuinely believed made a bms unsuitable for them. Non held water though, except for the case where somebody has a large number of cells they are forever reconfiguring. They just have to live life dangerously or buy a number of bms units to cover all the configurations they make. So they are cost driven to take some risk. Your not one of these people though. We have very few of them (and they don't need to ask advice)

Punky was asking if I sell them, not you. He is probably using the RC stuff himself, and does not like hearing that he spent more money buying less effective kit. I can't just sit here and say nothing though. This RC charging stuff has taken homes from forum members. Still it gets talked about though. I was shocked to read a long standing thread on this board that starts saying how lipo couldn't even use a bms, and it was only a couple of years ago. Pages of blind followers came next. There is some absolute nonsense being published by people that just don't get it. Thus the proper method has actually been ignored by many that still can't let go of the past.

If you look at an EV site you will notice a total absence of balance chargers. This is a different world. One of safety and ease of use. You can use the toy stuff, but if you do your only getting half the picture.

bms = cheaper easier and safer. What is not to like.

I'm sorry that most threads here point to RC stuff, usually being pushed by someone that has started fires and not learned from them. It is a bit sickening I know. Because all you want is the modern solution I'm sure. Resistance to change is holding a lot of people back though. Talk of rc charging still takes place, and people still have fires because of it. What can I do....


One drawback.... To use a bms your going to have to solder a few wires. Or get a friend to. Or I can link you to people that will resell a bms with plug&play leads attached for you.

If you want to see what can be done, start a new thread where we can talk purely about bms charging. It will be a good reference for others. Just tell us you want a bms setup for however many cells...
Or, you can drop on to my existing thread and ask anything you like. http://endless-sphere.com/forums/viewtopic.php?f=14&t=56886&p=856739&hilit=yginrut#p856739
Further reading: http://endless-sphere.com/forums/viewtopic.php?f=14&t=57221#p853835

Any pack you buy from china will contain a bms. Many threads about people designing and building them here too. It just seems when people talk about lipo the radio control methods get bought up again. It's a social situation rather than a technical one.


I will be more than happy to help with any questions and supplier information you need. I will design the whole thing if you like. We need more such threads to bury the out-dated one's in history.

 

[Punx0r]

Punky was asking if I sell them, not you. He is probably using the RC stuff himself, and does not like hearing that he spent more money buying less effective kit. I can't just sit here and say nothing though.

Is that a "yes" or a "no"? Just want to be sure, as I don't like making assumptions either way.

I've nothing against using a BMS. If it suits someone's requirements then go ahead and use one. As long as it's good quality. No point pointing the finger at shonky cheap Chinese balance chargers if the factory down the road makes separate BMSs to a similar design with the same counterfiet, over-rated components.

It would be nice to see some non-Chinese sources of high-powered, reliable, reasonably-priced BMSs. UK, Europe, USA etc. I haven't gone looking far, but can't recall seeing any yet.

It would also be nice to a technical discussion without deliberately emotive language.

 

[dogman dan]

Still no fires for me, but I have held a pack in my hand that was so hot the shrink was dripping off it.

That was a plug coming off a parallel harness, resulting in one pack discharged to 0v.

There are lots of ways to not over discharge. A bms is one real good one. But leave your bms plugged in for long enough, and it will over discharge a cell. The bms will shut off the current to the mains, and then happily keep running on that one cell till it reaches 0v.

Good way to start a fire with cheap RC packs. Perhaps why they don't sell them with bms? When this happens to lifepo4 and limn packs, they are ruined, but no fire. Have it happen with RC lico, and your house might burn down.

LVC set real high is not a bad way to avoid an over discharge.

The way I practice, is carry plenty of battery. So I very rarely get even close to a full discharge. I tape those parallel harness plugs now. I monitor whole pack voltage, and check individual cells often, but not every cycle.

The alarms work, some are too quiet. I have a few that are plenty loud, but using them means balancing the pack every charge. Like a bms, they run on one cell and unbalance the pack. Leave them plugged in all the time, it could burn your house down.

Anyway, over discharge, and the best charger in the world can't help you.

I have more or less settled on 14s, and am considering using a bms. But I sure as hell won't keep the pack in the garage with a bms attached.

Bottom line, don't trust these cells. Do it where you can have a fire is still the rule for cheap RC lico packs.

 

[wesnewell]

To answer the original subject question and bypass all the bs in between. the advantage is you can you can plug a 12s pack made of 2 6s packs directly into the balance ports of a 12s or 14s balance charger without having to make adapter balance cables. The advantage of using 4s packs to make a 12s pack is price. It may be cheaper for the same amount of power. It would also be cheaper if you had a cell failure to replace a 4s pack. Personally, I chose the one time chore of making the adapter cables, so I could save money. I run a 24s2p pack that I charge as a 12s4p pack using a 14s charger. I know of no bms on the market made for rc lipo, or one that has a high enough lvc to protect you from over discharging it. LVC for rc lipo should be no lower than 3.3V, and that will take the rc lipo cell down to 0% soc. You don't have to believe me, believe your own eyes.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=47294

 

[izeman]

you use a bms to safe the battery from DAMAGE. not on a regular base for power cut off. there is a programmable limit in every controller you should set to 3.5-3.6v per cell. if somehow the battery gets depleted even more there is the bms to safe the battery from over discharging. and therefore 3.0v is just fine.

 

[Punx0r]

Whilst that will prevent a serious over-discharge, it does nothing to prevent a weak or unbalanced cell from being discharged to near 3.0V on every cycle.

 

[dogman dan]

Sorry about the bms talk. But I just think it needs to be made clear that a bms does not mean you can skip the home quality control.

Step one with cheaply made RC cells is to find and get rid of any defective cells. Till you do that, you are playing with fire.

Then, if you don't go below 3.6v per cell average, you won't have a big risk of a weak cell diving below 2.7v.

FWIW, a functioning bms would have stopped the discharge that time my plug came undone and I held that melty pack. I would have saved a pack, and not had a close call with a fire. But nevertheless, these risky cells need to be stored and charged in a fire resistant place, regardless of how good or how cheap your charger is.

 

[Ykick]

Sorry about the bms talk. But I just think it needs to be made clear that a bms does not mean you can skip the home quality control.

Step one with cheaply made RC cells is to find and get rid of any defective cells. Till you do that, you are playing with fire.

Then, if you don't go below 3.6v per cell average, you won't have a big risk of a weak cell diving below 2.7v.

FWIW, a functioning bms would have stopped the discharge that time my plug came undone and I held that melty pack. I would have saved a pack, and not had a close call with a fire. But nevertheless, these risky cells need to be stored and charged in a fire resistant place, regardless of how good or how cheap your charger is.

Although culling-out dud(s) is a good place to start I tend operate under the premise these things are ALWAYS like playing with fire. Nearly 4 years RC Lipo service I've had seemingly good cells go downhill fast.

RC Charger, BMS, Fluke meter, message board noise, etc. Trust nothing, check everything then check it again with different meters, if possible....

IMO, these cells are best for "highly interested users" who truly desire to learn about pack construction, care & feeding. Capacity tests, checking IR, maintaining balance in series strings, etc. Casual users need not apply!

 

[dogman dan]

Agreed. We need to be careful what we tell folks to do. I worry that noobs get the idea just using a bms makes a cheap flamey cell safe. I worry that noobs don't take the fire warnings seriously. All my RC lico is sitting in steel boxes in a fireplace right now.

BMS plus quality cells is the ticket, if you can afford them. Like a cellman pack.

 

[dnmun]

except there has not been a fire while charging lipo using a BMS but there have been two fires using balancing chargers and one fire from bulk charging without a BMS.

everyone goes on and on about how low voltages lead to fires or how a BMS causes fires or how aa BMS drains the battery pack to zero and other nonsense.

the facts are: balancing chargers 2. bulk charging 1, BMS 0

there are no other reported fires here.

 

[izeman]

i may add, that even though i use a BMS for all my batteries, i have several RC chargers: from junsi 206b to BC168, maxpro6 and several others.
and i would NOT call them toys. they have the very same methods to measure voltages and take care of them as a BMS. it's just that the bms is built INTO the charger and not external.
the great risk i see with RC chargers is, that you have to do too much connecting and disconnecting, too many things to do something wrong. from wrong polarity to lose balancing cables/connectors, to wrong charging values etc ... and that the way to make battery charging and discharging is to make it as bullet proof as possible. no matter what chemistry you use.

 

[wineboyrider]

I suppose there are many camps here on ES. I like the safer lifep04 for plug and play use, but have been buying mostly lipo lately. I reckon it's like in the ICE world where some people love straight pipes and removing their starter to lessen the weight of the vehicle. I use lithium to commute everywhere so I would really prefer a plug and charge method. I have had the most luck using lipo as booster packs with my lifepo4 pack for longer or quicker rides.

 

[friendly1uk]

Whilst that will prevent a serious over-discharge, it does nothing to prevent a weak or unbalanced cell from being discharged to near 3.0V on every cycle.

Sorry, I thought the 'do you sell them' question was a gag. Of course I don't.


I'm not sure what i just quoted. I think your saying Radio control chargers offer no protection while riding so could cycle a cell down to 3v while the others were still at 4v, and in fact that 3v could drop to zero volts on that cell before controller lvc operated. Then your charger would likely just carry on charging the pack regardless, as overall it is a dumb charger. Not an active bms that could be present in use and see such an imbalance between cells, Stopping further charging until it got the needed attention. Although a well set up system would of given early warning by cycling the charge light to show balancing was not completed before the end of charge (I don't think I have heard anyone else cotton on to that one)


In shut down mode, my bms consumes 0.00002 amps. Thus, If I put my rather small 5Ah pack away with a 50% storage charge I will hit lvc in about 14 years. As the pack will die of old age long before then I can't see the point on disconnecting it for storage. You could in fact damage a bms by pulling it's main wires with the balance wires still intact, so it seem like a lot of fuss with no real gain to me.
The alter: http://www.mad-professor.co.uk/Datasheets/O2Micro/OZ890.pdf

I actually plug my stuff together and use it. I can't read a cell voltage any better than my bms can. I am of no use to it. I do have an RC charger though, as it runs 12v and does lots of tricks so makes a nice enough spare should my main charger go down. There really is no requirement for the user to do anything though. No manual would suggest such a thing.

 

[Punx0r]

I think your saying Radio control chargers offer no protection while riding so could cycle a cell down to 3v while the others were still at 4v, and in fact that 3v could drop to zero volts on that cell before controller lvc operated. Then your charger would likely just carry on charging the pack regardless, as overall it is a dumb charger.

No. What I was saying was that a BMS will do this (the part in bold), if the LVC is not adjustable. Setting a total pack LVC on the controller will not help. A RC charger will not charge begin a charge if a cell is under or over-discharged.

 

[wesnewell]

In shut down mode, my bms consumes 0.00002 amps. Thus, If I put my rather small 5Ah pack away with a 50% storage charge I will hit lvc in about 14 years. As the pack will die of old age long before then I can't see the point on disconnecting it for storage. You could in fact damage a bms by pulling it's main wires with the balance wires still intact, so it seem like a lot of fuss with no real gain to me.
The alter: http://www.mad-professor.co.uk/Datasheets/O2Micro/OZ890.pdf

Why don't you provide a link to the bms you use, rather than a link to a pdf for an oz890 processor chip. is this the bms you use? It doesn't match your claims.
http://apollogroup.com.hk/china/lidian05.htm