BMS with optional Bottom and/or Top Balancing

[john61ct]

The CellLogs have been unavailable forever now, hundreds of threads bitching and moaning about it

everyone knows they aren't coming back.

And they were just OK, for the price, nothing all that great intrinsically.

All there in the threads if you just go back, search and read them.

 

[john61ct]

BM16LP v2 can apparently drive a relay not just alarm

Among cheap chinese components many like Chargery products, probably worth trying

please report back

 

[john61ct]

Also if we're talking LFP rather than other LI chemistries, you want the BM16LF not the LP version

maximum top charge is usually 3.6V, but for me that is too high for longevity.

I recommend 3.45Vpc if C-rate is low, maybe 3.50V if higher.

So an adjustable charger or HVC would be much better.

 

[zeccato]

,.......
>

If you get a proper adjustable HVC that cuts off the charging when target voltage is hit, that is fine.
.....
The BMS HVC is there as a backup, failsafe, to protect the pack when the primary control fails.
......
Just using an alarm is A Bad Idea.

If v series of the battery becomes defective, if you charge it without bms, with any charger (no balance), some series could go overvoltage.
And sometimes it can also happen with some bms.

which is why I'm looking for a HV alarm.

 

[zeccato]

BM16LP v2 can apparently drive a relay not just alarm

Among cheap chinese components many like Chargery products, probably worth trying

please report back

thanks.
Maybe I'll buy this one as soon as I buy the li-ion battery.
(they also sell it in Germany).

 

[spinningmagnets]

I've read some persuasive arguments for bottom-balancing of LiFePO4 packs, but I must confess that I have no experience with them.

 

[eMark]

I've read some persuasive arguments for bottom-balancing of LiFePO4 packs, but I must confess that I have no experience with them.

Does he even bottom balance the P-groups before he does his quick charge? Does he even have a $10 8S cell-log to check the P-groups min-max voltage disparity before and after his quick charge? What is the C-rate of his quick charge on his 8 yr old LiFePO4 ?

What cautionary suggestions might you recommend ??

Battery pack is 8 years old without a BMS. When he wants to make a quick charge, without using his balance charger, he charges it to 95%. Does he use an inexpensive 8S cell-log to check the P-groups min-max voltages before and after his quick charge? He would like to find two 8S HV alarms to plug into the two balance leads as one option for alerting him to the possibility that one of the P-groups may be over 95% when quick charging instead of balance charging.

Get the picture? Could offer my two cents, but coming from you would be better :thumb:

What is the min-max P-group disparity (e.g. 80mV, 150mV, 300mV) you'd shoot for before quick charging his 8 yr old battery?

If you are referring to balance charger is ok,
but I already have it.
And I already have the charger Adjustable 0-60v 0-11A c.c c.v.
I have also an old battery (8 years) 16s 30Ah lifepo4
and when I don't want to balance it,
I charge it (without bms) at 95%.,
for when I make a quick charge,
for this for more security I'm looking for a HV alarm 8s or 16s, NOT a HVC. not Bms.

 

[zeccato]

.

Does he even bottom balance the P-groups before he does his quick charge? Does he even have a $10 8S cell-log to check the P-groups min-max voltage disparity before and after his quick charge? What is the C-rate of his quick charge on his 8 yr old LiFeP04 ?

What cautionary suggestions might you recommend ??

Battery pack is 8 years old without a BMS. When he wants to make a quick charge, without using his balance charger, he charges it to 95%. Does he use an inexpensive 8S cell-log to check the P-groups min-max voltages before and after his quick charge? He would like to find two 8S HV alarms to plug into the two balance leads as one option for alerting him to the possibility that one of the P-groups may be over 95% when quick charging instead of balance charging.

Get the picture? Could offer my two cents, but coming from you would be better :thumb:
For instance what is the minimum min-max P-group disparity (e.g. 30mV, 60mV, 100mV) before quick charging his 8 yr old battery?

If you are referring to balance charger is ok,
but I already have it.
And I already have the charger Adjustable 0-60v 0-11A c.c c.v.
I have also an old battery (8 years) 16s 30Ah lifepo4
and when I don't want to balance it,
I charge it (without bms) at 95%.,
for when I make a quick charge,
for this for more security I'm looking for a HV alarm 8s or 16s, NOT a HVC. not Bms.

I don't feel like writing long speeches.
the things I use are written under.
My balancer balances right away.
1 question: no. it's useless to balance them first, because the lowest volts usually fill up first.
P-group disparity 03v.
but when I don't use it for weeks, after the quick charge at 4-7A
1 parallel remains 50% unloaded,
and load it individually at 4A,
weird, but it works fine on the road.

I should check it out,
but as long as it does 50 km, controller 48v 35A is fine by me.

 

[john61ct]

It really does not matter where the balance point is, so long as you match your usage accordingly. Accept that the weakest cell (grouo) dictates the range of the whole.

So, if your usage means you will eke out every last Ah at the bottom SoC% then bottom balancing is safer, no BMS needed while discharging. And the only place to worry about the imbalance delta is the point where you target them being balanced.

So if top-balancing, who cares how imbalanced they are before charging?

If bottom balanced, then don't worry about imbalances after charging, when you pick up one end of the stick, you also pick up the other.

No per-cell monitoring is needed while charging every time either, as long as you have mapped out the pack level voltage HVC that corresponds to your weak link hitting the max you want to allow.

If you're doing things right, your LFP cells may still be very healthy and stay balanced for another decade, re-balancing maybe only annually if that.

People with healthy cells re-balancing frequently are IMO doing it wrong.

 

[eMark]

So, if your usage means you will eke out every last Ah at the bottom SoC% then bottom balancing is safer, no BMS needed while discharging. And the only place to worry about the imbalance delta is the point where you target them being balanced.

If bottom balanced, then don't worry about imbalances after charging, when you pick up one end of the stick, you also pick up the other.

I've read some persuasive arguments for bottom-balancing of LiFePO4 packs, but I must confess that I have no experience with them.

zeccato, if time permits at least try to make time for some bottom balancing (time permitting when needed).

It's a good practice to check your P-group min-max voltages with a 8S Cell-Log before you decide to "quick charge". Maybe, a good idea (even if you don't know whether your next charge is a quick charge or balance charging is to plug in an 8S balancer to bottom balance soon after a pack discharge. Then should you later decide you need to do a quick charge it will already have partial or as good bottom balancing as possible. That's what i do, but i never charge over 2.5A (0.83C) and time permitting usually 1.5A (0.5C).

It's good practice when possible to occasionally bottom balance (as needed) before quick charging. Then you shouldn't have to worry if you're never able to find HV Alarm. So, a little 8S Cell-Log is almost a must to check the min-max disparity of the P-groups, like before quick charging, when you already have balance leads for balance charging ... always striving for as little P-group voltage disparity as possible considering the condition of your 8 yr old pack.

If you had a 14S pack i'd suggest a Tenergy 5-in-1 Intelligent 2S-7S Cell Meter as it also has an IR function. I have both it and the IDST BattGo 8S. It's a little pricier, but it has other options that i really like. Check it out ...


https://www.amazon.com/ISDT-Battery-Meter%EF%BC%8CLCD-Capacity-Balancer/dp/B07797N9BG/ref=pd_bxgy_img_2/139-5157333-5670654?_encoding=UTF8&pd_rd_i=B07797N9BG&pd_rd_r=1f597735-e36c-400a-9f95-2155fb331708&pd_rd_w=HMBAv&pd_rd_wg=FTQlK&pf_rd_p=fd08095f-55ff-4a15-9b49-4a1a719225a9&pf_rd_r=VZPGRN0QX09NEY2NKG96&psc=1&refRID=VZPGRN0QX09NEY2NKG96
https://www.youtube.com/watch?v=CDhlq6QkFi8

Also, if you don't already have one consider these 2 as 1 of them may not be enuf over time and wear ...
https://www.amazon.com/dp/B00XQ91ECA/ref=psdc_2234134011_t1_B0064SHG0Y

 

[john61ct]

There are no CellLogs anymore as you've already been told.

99.99% of users do automated top-balancing. There is no point to bottom balancing, unless that is the only balancing you do.

There is also no point to check for imbalance, except at the voltage where you do your balancing, again as you've already been told.

 

[eMark]

There are no CellLogs anymore as you've already been told.

99.99% of users do automated top-balancing. There is no point to bottom balancing, unless that is the only balancing you do.

There is also no point to check for imbalance, except at the voltage where you do your balancing, again as you've already been told.

That's the purpose of these ES threads to discuss the pros and cons. By 99.99% of users i take it you mean 100% of smart DIY ebiker pack builds use a smart bluetooth BMS.

zeccato has previously indicated that his next DIY build will be with a smart bluetooth BMS :thumb:

PS: You previously said your preference was for middle balancing.

 

[zeccato]

There are no CellLogs anymore as you've already been told.

99.99% of users do automated top-balancing. There is no point to bottom balancing, unless that is the only balancing you do.

There is also no point to check for imbalance, except at the voltage where you do your balancing, again as you've already been told.

I agree and I quote, you spared me the answer.

 

[zeccato]

[quot id]

zeccato has previously indicated that his next DIY build will be with a smart bluetooth BMS :thumb:

PS: You previously said your preference was for middle balancing.
[/quote]
maybe I was thinking, but for now I've decided NO BMS.
Maybe it's mistranslated,
or you haven't read my answers carefully.
and I've said it many times no Bms.
and I repeat: I already have the Charger Balancer 14s: TP1430C. 

And as a display Hv alarm no bt, all I could find was the Chargery BM16, 3-16s.

 

[john61ct]

By 99.99% of users i take it you mean 100% of smart DIY ebiker pack builds use a smart bluetooth BMS.

I meant nothing of the sort. What I said was, 99.99% of users do automated top-balancing.

There are hundreds of devices used to accomplish that. Yes, most often some sort of BMS.

But I am not commenting on, nor recommending any general category here.

**Stop** putting words in other peoples' mouths dude.

 

[john61ct]

maybe I was thinking, but for now I've decided NO BMS.
Maybe it's mistranslated,
or you haven't read my answers carefully.
and I've said it many times no Bms.
and I repeat: I already have the Charger Balancer 14s: TP1430C. 

And as a display Hv alarm no bt, all I could find was the Chargery BM16, 3-16s.

And? Are you going to buy that then?

I'm not saying you should "use a BMS" as in all the time.

But, if the BM16 does not suit you (why not?) then using (whatever) BMS just for charge control, will give you more than just an alarm, actually terminate charging of your PSU when any cell hits your HV setpoint.

 

[zeccato]

maybe I was thinking, but for now I've decided NO BMS.
Maybe it's mistranslated,
or you haven't read my answers carefully.
and I've said it many times no Bms.
and I repeat: I already have the Charger Balancer 14s: TP1430C. 

And as a display Hv alarm no bt, all I could find was the Chargery BM16, 3-16s.

this answer was for eMark not referring to you, sorry.
I corrected.

 

[zeccato]

[/b].
s.

And? Are you going to buy that then?

I'm not saying you should "use a BMS" as in all the time.

But, if the BM16 does not suit you (why not?) then using (whatever) BMS just for charge control, will give you more than just an alarm, actually terminate charging of your PSU when any cell hits your HV setpoint.

the Bm16 satisfies me for now, and maybe I'll buy it,
after I've investigated.
excuse for the confusion.

 

[eMark]

The Chargery BM16LF V4.1 ... if available through Ali may be just what you're after. Here's a few of its specs ...

• During battery charge, if any of its cell voltage over setup value or battery temperature over setup, the BM16LF can sound and LED flash alternately to prevent any cell (by cell they probably mean P-group) from over charge.

• In any case, when cell voltage (P-group) difference is over setup value the unit can alarm.

• Over charge warning voltage: 3.40V ~ 3.90V per cell, step 0.01V, default 3.70V

• Over cell difference warning voltage: 0.010V ~ 0.200V per cell, step 0.005V, default 0.100V

http://www.chargery.com/doc/Chargery%20BM16LF%20specification%20%20V4.1.pdf

View attachment 1


A smart bluetooth BMS data sheet implies it reads the voltage of each cell, but more likely average P-group voltage ... which is still representative of the individual cell voltages in each P-group. If one of the P-groups has more disparity than the other P-groups it could be an indication there's at least one problem cell in that P-group.

 

[john61ct]

Is "P-group" something you coined?

By definition while in a group all the cells have to remain at exactly the same voltage all the time, even if old and at varying capacities.

In other words, a group of cells (which already means "connected in parallel") acts as a single cell.

So saying "measures the cell voltage" and "measures the voltage of each group" is in effect saying the exact same thing.

It is impossible to see any differences between the cells in a group, until the group is "atomised" into individual isolated cells.

 

[zeccato]

The Chargery BM16LF V4.1 ... if available through Ali may be just what you're after. Here's a few of its specs ...

• .

• : 0V ~ 3.90V V

• : 0.010V ~ 0.200V

http://www.chargery.com/doc/Chargery%20BM16LF%%20%20V4.1.pdf

we discussed here:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=40628&start=25

now with the shipments I think it's a problem, for me self sell it in eu,
the manual is there:

https://shop.lipopower.de/Battery-Monitor-und-Saver-fuer-3S-bis-16S

http://www.litrade.de/shop/BMS,Balancer/BMS,Systeme/Akkumonitor,Chargery,BM16,BMS16,bis,16,Zellen,Kapazitaetsanzeige.html?listtype=search&searchparam=monitor

 

[eMark]

Ok. then let's backup again to the thread Title (balancing) and your interest in just a monitor (i.e. CellLog 8M). You indicated you can balance charge your 16S LifePO4 which i questioned... That's why i previously said to another member ... "Get the picture?"

Here's your post from another thread implying your 16S pack can be split or at least has two 8S balance leads for cell monitoring ...

All I care about is the monitor,
and maybe disable the balance,
I need it to charge 2 battery 16s lifepo4 without the bms, up to 90-97%..
as discussed here: but
https://endless-sphere.com/forums/viewtopic.php?f=14&t=104641&p=1529737#p1528905

When you say "charge 2 battery " ... 16S LifePO4 (?) ... do you mean you can split the 16S into two 8S packs that you combine after balance charging your two 8S packs and then again joining as a 16S battery?? Even if that was/is the scenario the only 8S balance charger i know of is the iDST Q8 smart charger ... https://www.youtube.com/watch?v=BqgEEuquX_Q ... but it's single (not available as a 8S duo ... aimed more at RC quadcopter guys. So, that's why i question whether you've ever balance charged your 16S, unless you've modified/built your own custom duo 8S charger when balance charging your two 8S packs of your 16S LifePO4 as you've previously implied.

If you had bought the iDST BattGo 8S a couple years ago, if just for cell monitoring or also bottom and/or top balancing (when necessary) you possibly wouldn't be posting now in search of an add-on overcharge alarm/buzzer. Kid you not, because two years ago you would've known if your 16S was still safe to bulk charge to 95% OR time to retire it so you don't run the risk of a FIRE.

Please don't get upset with me, but when previously replying to another much respected member "Get the picture?" this is what i pictured. ... You have an 8 yr old 16S battery that may or may not have two 8S balance leads in the event you were hoping to still find at least one new or used CellLog 8M monitor. Or possibly you had one, but it is no longer working. The cells in your older 16S pack may now be unbalanced before and after bulk charging ... that's why you want a charger with alarm if one of the P-groups is borderline dysfunctional. Hope what you really meant by "quick charging" is bulk charging at no more than 1C and preferrably 0.5C considering the age of your 16S.. Thus your reason for NOT fully charging (maybe only 90%). Do you realize the risk of a FIRE even to only 90% without cell monitor for bottom discharge balancing as needed (cells within 30mV min-max goal).

So, assuming you can split your 16S battery into two 8S packs with 8S balance leads attached to each 8S pack you first need to monitor and bottom balance (discharge balancing) each 8S pack to within at least 30mV if even possible. The CellLog 8M was only a monitor. The closest (best replacement) for the CellLog 8M is the iDST BattGo 8S. It not only monitors, but discharge balances as well as other neat features. So, the first thing you need is an iDST BattGo 8S or possible two with your two 8S balance leads.

That other iDST BattGo 8S video is a joke, yet good to see so you don't think every review gets reimbursed. The guy has a ton of usually good videos, but he's so busy he doesn't always do justice when reviewing a new product which was the case with that video review of the BattGo 8S. Does he actually thinks that was a fair test seeing how long it takes to discharge a cells having a disparity of 450mV higher than the other cells... give me a break! What is does show is the bias that many DIYers still think is the best 8S monitor (CellLog 8S). Once they get there hands on a BattGo and realize all it can do and will do they wouldn't use their CellLog 8 anymore.

One of the best reviews (German) ... https://www.youtube.com/watch?v=fUokWECN2cI&t=27s
This is another decent review ... https://www.youtube.com/watch?v=UIYCKYfNkiE&t=563s

So in summary the iDST BattGo is actually better than the CellLog 8M (some CellLog 8M diehards may disagree until they get one) as it can also bottom and/or top discharge balance assuming you really have two 8S balance leads attached to your 16S battery.

So, to summarize your 8 year old 16S LiFePO4 battery may need to be retired. BUT should you decide to still continue to bulk charge it (preferably at 0.5C) you first need to get a BattGo 8S if you have two 8S balance leads on your 16S battery. The battery only needs to split in two 8S packs when actually balance charging assuming you really have two identical 8S balance chargers starting the same time with the same settings or a duo 8S smart balance charger. You don't need to split it into two 8S packs with passive 16S monitoring or discharge balancing with the two 8S balance leads attached to your 16S LiFePO4 ageing battery.

Hopefully, this post is useful :wink:

 

[zeccato]

I'm continuing the discussion here:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=104390

anyway: I have two lifepo4 batteries
1°= 48v 30A 2-3c.
2°= 48v 7,5A 30c
no need to advertise the balancers,
I repeat, I have already 14s balancer 1000w
THUNDER POWER RC 1430C DC
and I balance at 8s at a time,
the battery doesn't split,

if you can shorten your answers.
sorry everyone for the confusion.

 

[john61ct]

Full of misinformation, as well as way too long wall of text man.

the only 8S balance charger i know of is the iDST Q8 smart charger

That's just ridiculous, for sure there are dozens if not hundreds of different chargers can do 8S just fine, including many much better than IDST.

And no need for a Duo unless that is specifically needed.

_____
What is this ""two years ago" nonsense, and why plug the BattGo specifically? Not saying they aren't fine, but no need to spout on for hundreds of words acting as if they are the only solution.

Again CellLogs, are gone, why keep mentioning them at all?

> you would've known if your 16S was still safe to bulk charge to 95% OR time to retire it so you don't run the risk of a FIRE

Gross fear-mongering.

Bulk charging to whatever definition of 95% is always going to be safe so long as monitoring of cell level voltage and temperature is part of the process. Being unbalanced no matter how much is not a safety issue.

Another bit of misinformation, neither is high current "fast charging", the reason to keep C-rates down is prioritizing longevity only, just a matter of preference not a safety issue so long as proper infrastructure.

And again, for LFP 8 years is not an old pack, I've seen many dozens still close to 100% SoC at a decade or longer, there is **no** indication here it is even worn much less nearing EoL.

Plus a basic voltage checker will reveal nothing about battery State of Health or how close to EoL it is.

And why keep harping on bottom balancing? Again (and again) irrelevant here, and to anyone using a balance charger.

Please stop wasting our time giving others advice on topics you've been corrected on over and over.

Put your energy into your own learning, feel free after googling to ask specific **concise** questions in an appropriate thread asking for clarification on the many issues you're still not clear on.

Short posts, to the point, one at a time please.

 

[eMark]

anyway: I have two lifepo4 batteries
1°= 48v 30A 2-3c.
2°= 48v 7,5A 30c
no need to advertise the balancers,
I repeat, I have already 14s balancer 1000w
THUNDER POWER RC 1430C DC
and I balance at 8s at a time,
the battery doesn't split,

Only problem is you implied/wrote 16S in several posts ...

battery cell monitor BM16 2? or 3S-16S, (chargery.com).
similar?:
Battery cell monitor Saver BCM16 3S-16S,

I need it to charge 2 battery 16s lifepo4 without the bms, up to 90-97%.,

I charge it (without bms) at 95%.,
for when I make a quick charge,
for this for more security I'm looking for a HV alarm 8s or 16s, NOT a HVC. not Bms.

I found this 16s, but I don't know if it's good, see:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=55601&p=831520&hilit=BM16LP#p831520

OK, so what you could have used before now is the Tenerty 5-in-1 Intelligent 7S Cell Meter (with IR feature) for both cell monitoring and discharge bottom balancing before charging. It's only $15, maybe get a couple ...
https://www.amazon.com/Tenergy-Battery-Intelligent-Digital-Balancer/dp/B0178P8H9U
https://cdn.sparkfun.com/assets/0/3/a/2/2/01444_manual.pdf

[youtube]2JoBG2W5n24[/youtube]

No problem still hope its useful :thumb: