Issues balancing with Batrium BMS

[sunshine_eggo]

This ( very important task) all seems to come across as smoke and mirrors - all a bit magical and secretive ?

Just because it's not obvious to you doesn't mean it's magical or secretive.

Can I trust the BMS to do its job by itself or have I got to keep hovering over my bank (like a new mother over a cot with sleeping babe)

I almost never do anything with balancing. When I do, it's 30 seconds of effort to make a change. If I chose a "set and forget" option, I would never have to do anything with balancing unless my battery is failing.

Worse still can I delegate this responsibility to an employee - you know what thats like!

That depends on your competence as a manager/trainer and the robustness of your process.

Is the system smart enough to give me graded error reports periodically eg advisory, intervene, critical.

No. As this system is designed to be flexible enough to be usable on a variety of cell types and sizes, it can't be pre-loaded with the expertise of an unknown configuration.

I dont want to stew over a spreadsheet full of figures. Are data logs saved regularly so no data is lost with power upset.

There are a variety of logging options.

This is a DIY forum. If you're going to build your own battery, you need to be THE expert on YOUR battery at the end of the process. Since this seems to be unacceptable to you, I recommend you pursue commercial solutions that require little learning and less expertise than you are willing to develop.

 

[Zwy]

This ( very important task) all seems to come across as smoke and mirrors - all a bit magical and secretive ? Can I trust the BMS to do its job by itself or have I got to keep hovering over my bank (like a new mother over a cot with sleeping babe)

First decide what you want for cell voltage at full charge. I use 3.46V and multiply that by 16 cells to get 55.36V.

I charge to 55.5V, set bypass volts at 3.46V let the K9's do their job. Depending on how well your cells charge with any runners really determines where to put settings. I changed bypass start over 3.40V to 3.39V and cells reacted to the change by balancing much better with lower delta. I don't use autolevel, I tried it but found it doesn't really make a difference. I have 2 runners out of 64 cells. The worst cell will run up to about 3.55V during bulk charge and the lowest cell was at 3.40V and bypass begins if the cells have not hit 100% SOC for several days in a row and no bypass had occurred. The idea was to engage bypass sooner to begin pulling off that high cell. The major runner was from some cheaper cells I purchased that were not matched for internal resistance. I might just pull those out someday, install 16 cells matched for internal resistance and use the cheap cells in my golf cart.

Worse still can I delegate this responsibility to an employee - you know what thats like!

Is the system smart enough to give me graded error reports periodically eg advisory, intervene, critical. I dont want to stew over a spreadsheet full of figures. Are data logs saved regularly so no data is lost with power upset.

I don't know what you're looking for. What do you need a bunch of data for? Only time I could see is if you are having a problem with the BMS going critical and tripping the shunt trip. Then you would look into the logs.

I just have a laptop that sits in the kitchen with all the cells displayed. I also can look at the Batrium screen at my desk in my shop on that laptop. What other information would you need on a day to day basis, the screen is displayed to indicate SOC, cell voltage, charging rate and cell temp. Once you have this setup, it runs itself. You can make an adjustment here or there in settings to fine tune things, but as long as you see cells under 50mv delta when bypass is done, it is good to go.

 

[Boron]

@sunshine_eggo , 2 great nations divided by a common language. I found this when I worked in Tx - they thought I was from Boston. My observations on BMS were derived from other members' comments and Vids and the sometimes unreliable behaviour of BMS's and interfacing with the demands of the MPPT.

That depends on your competence as a manager/trainer and the robustness of your process.

You must be referring to Elon
Q
Is the system smart enough to give me graded error reports periodically
UQ

I daresay we are only a heartbeat away before AI appears and takes over the whole shebang with an Alexis reporter. That could work

thnx 10^6 for all your generous minded help

 

[Boron]

I have a 4-battery packs with cells in 16S (EVE 280K) and am using the WatchMon-CORE kit with a CellMate-K9 for each pack. I have had issues with a few cells not staying balanced in different packs. What is confusing to me is the voltages batrium is reporting...if my pack voltage is 55.20 that would mean I should either be at 3.45 at each cell OR some cells should be above 3.45 and some cells should be below 3.45. In the screenshot below, you can see none of the cells are above 3.45 but there are 3-4 outliers below with the lowest at 3.38

I don't understand how that can be, and I'm a bit frustrated I can't get my cells in balance. I want to avoid having to open my pack and manually balance them. My charge controller is set to bring the pack up to 55.2V (3.45/cell) for 1-hour, and then go to float at 53.6. My batrium BMS is set to start balancing at 3.45, so any cell above 3.45 it will start using it's resistors to bring the cell(s) down.

I can't get these few cells back into balance for the life of me. What am I missing here? How can the pack be at 55.20 when not one cell is above 3.45 but multiple cells are below?

Any help/input appreciated, thank you.

View attachment 132376View attachment 132377

It does make you wonder about the mysterious workings of these wizard BMS balancers and it seems to me that the Marketing Depts have found a means to confabulate the whole industry with proprietorial magic with super hype claims and $$$$ cost to go with it. After all, back to basics, what are we really trying to do? Adjust charge rate to suit individual battery needs - given that not all of the 100's of 18650's say in a powerwall are born equal.
Those early recyclers from10 years ago discovered mountains laptop battery packs which were deemed "worn out" when in fact they needed simple re-balancing after a few years of use and were good to go for many more years (as my personal experience found when I forcibly dismembered the battery packaging and performed a crude recharging of individual cells (3s,4s)). I now have a very usable collection of premium grade laptops with my coveted Win XP SP3 OS available for use as required (bought off Ebay for $ when they first cost $$$$).
Thats what Industry Hype and Marketing mischief does to us all
Fortunately we have a site like this where Users can share their own experiences

Well given all that yada yada - my current frustration is (as per OP) monitoring and controlling of all these cells. How can this be done reliably. If I have to spend countless hours puzzling over the deliberately mysteriously working of a Makers system cos its not up to spec as claimed then its surely failed in its job. I have seen several posts of poor performance from the above - didnt live up to its promise - no support from maker - and so on.
Industry would have you believe that you must constantly fret over balancing when reality shows that you maybe only need to address such matters once a month after a full charge. Im sure the venerable Mountain Off-Gridders have years of experience here and dont get cheated so easily.

Notice how these systems (supposed to take the grief out of manual balancing of 100's of cells), instead flood you with a massive amount of figures flashy graphs and loads of parameter knobs to fiddle and adjust. Before all these bells and whistles you never had any of this info overload (as per my laptop example above). Your battery pack capacity just faded (as with lead acid AGM batteries - what a massive con trick there) as cells came out of balance .

Whats the answer?

IMHO - AI
I think within a year there will be AI apps that can digest all this data and present you with the Executive Summary - ie do this.

Im in favour of controlling your own data. Make your own measurements. I recently came across small 5 digit accurate Volt meters on Ali. for ca £3.50 each - what a bargain. These cheap 4 digit display are useless here. You need 3.765V +/- 5mV.

Sadly - industry dirty little secret - there is no cheap ready made equivalent of the Electomech relay SPDT (or better still DPDT), so scanning all your cells with a DVM cant be done cheaply in solid state (yes there are differential DAQ systems $$$$$ - very silly money).
However the old school EM relays are plentiful, cheap and reliable - to wont fail disastrouly to s/c. Scanning speed can be 1cell/sec. Even the humble Arduino can collect the data for you and send it to your PC in csv form which you port to Excel and have fun. You are in control.

So I propose an array of DPDT relays across of power wall, that can be addressed and periodically scanned across an entire bank and the data collected/ charge adjusted by whatever means you choose. Does it sound ridiculously crude and messy - or do you prefer a mysterious balancer you cant understand and dont trust? With this crude array your own system can determine which individual cells to fix and inject/extract using addressable relays as needed.
Thats all from my Colorado Cabin (I wish) - Garden shed. Watch out for vested interests who roam around sites pouncing upon heretics like me who dont support the Party Line. Just cos Im paranoid doesnt make me wrong