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chef
12 March 2011, 2004
This thread will try to categorize the types of BMS's, their overall approach to battery management and differentiating features. It's a high-level description and I welcome discussion drilling down into the gory details. This is meant for others as much as myself to keep things straight in my head. And to keep me honest in exposing how little I know :p
I will endeavor to update this post with additions and corrections.

I'm assigning a grade level for each major category. Some ElMoto'ers have used it and I've seen it referenced on other boards, though there doesn't seem to be industry standard terminology yet. Each level includes the features of the previous levels (for instance, Level 2 has all the features of Level 1 & 0).

Terminology --
BMS: Battery Management System
HVC: High Voltage Cutoff
LVC: Low Voltage Cutoff

Level 0: Pack voltage monitoring only. Pack HVC & LVC are usually included. It could be argued that this is not a BMS, though technically a battery is a collection of cells and pack monitoring is a rudimentary way of managing the battery. Some consider this equivalent to not having a BMS. Others believe that this is all that is needed if the pack is bottom-balanced before installation and drift is negligible.

Level 1: Cell-level voltage monitoring with cell-level HVC & LVC. No balancing, just monitoring of voltage on every cell. Charge is stopped when any cell hits HVC. During discharge, limp mode or shutoff is engaged when a cell hits LVC. The BMS must be able to shut off the charger (HVC) or signal the controller to reduce load (LVC).
Voltage data logging is an additional feature provided by some L1 BMS's.
Cell temperature readings and logging are provided by some L1 BMS's, though this tends to be more common in L2 BMS's.
These types of BMS's typically require pre-balancing the cells before installation (top-, mid- or bottom-balanced).

Level 2: Automatic top-balancing* through individual cell shunts, charge shuttling and/or charge bypass. The BMS's goal is to bring each cell up to its maximum capacity. There are a number of approaches, but in all cases a circuit attaches to each cell to direct the charge.

Shunt balancing shuts off the charger when a cell hits HVC. The cell is bled down with a shunt. Charging resumes after some time. This repeats until all of the cells are topped off.
Proper bleeding of the cells is crucial to prevent overcharging. Unfortunately it can be difficult to determine which BMS's do this properly before purchasing.
Charge shuttling is similar to (i) but the cell's charge is transferred to another cell instead of being shunted. Additionally, charge may be transferred during discharge for continuous balancing. Less energy is wasted but the circuitry is more complex.
Charge bypass on an individual cell level. The charger remains on and the circuitry routes around the full cell. Challenges are high current handling and/or granular control of the charger. This feature might belong under L3.

[*It's theoretically possible for a BMS to do mid or bottom balancing, though I've not seen such on the market yet.]

Level 3: Cell-level bypass during charge and discharge. This is functionally equivalent to removing a depleted cell and placing a short in its place during discharge. The pack continues to operate using the cells which have charge remaining. Pack voltage is reduced for each cell that drops off until it hits pack LVC. This is no simple feat as the current bypassed can be in the hundreds of amps.

chef
12 March 2011, 2005
This post is a placeholder for links to BMS's on the market and will be updated periodically. It's unlikely to ever be complete as the number of BMS's seems to grow exponentially. Please PM me or post a reply with information about a BMS not on this list.

Level 1
Mini BMS by Clean Power Auto (http://www.cleanpowerauto.com/MiniBMS.html)
ThunderStruck BMS-II (http://www.thunderstruck-ev.com/Manuals/BMS%20instrux%20-%20ver%205.pdf)
CellLog 8s (http://www.jun-si.com/UploadFiles/CellLog_8S.pdf) [Review (http://sites.google.com/site/tjinguytech/reviews/celllog)] (really more of a data logger than BMS, though its alarms can be adapted for HVC & LVC. See Bruce's circuit (http://www.elmoto.net/showthread.php?914&p=8344#post8344))
Chargery BM6 (http://www.chargery.com/cellMonitor.asp)
Chargery BS6 (http://www.chargery.com/cellSaver.asp)
Signalab BMS (link?)

Level 2
Mini BMS with optional shunt balancing (see link under L1)
Modalis BMS sold by Electric Motorsport (known to excessively overcharge cells)
Elithion Lithiumate (http://elithion.com/lithiumate-pro-controllers.php)
Wicom Auto EMS (http://www.evequipmentsupply.com/media/images/BMS/Energy_Management_System_REV_A.pdf)
Elite Power Solutions BMS (http://www.elitepowersolutions.com/bms-overview.html) (only available for GBS cells)
Manzanita Micro MK3x8 (http://www.manzanitamicro.com/products?page=shop.product_details&flypage=flypage.tpl&product_id=54&category_id=22&vmcchk=1)

Level 3
[Haven't been able to dig this up. Searching the TS group is... difficult]


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Handy BMS selector
http://liionbms.com/php/bms-selector.php

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Other BMS lists:
http://liionbms.com/php/bms_options.php

DaveAK
12 March 2011, 2019
Mini BMS can also be bought as a balancing BMS, i.e. Level 2.

chef
12 March 2011, 2026
Thanks for the heads up about the MiniBMS. Didn't see it at first but their PDF mentions "Optional shunt balancing"

Nuts & Volts
12 March 2011, 2041
Sweet thread. I am glad this topic was posted. I'll add a sticky to this.

You can add Elite Power Solutions BMS to level 2. It offers programmable balancing, programmable cell level HVC and LVC, cell temp readings and cutoff temp. It can display pack level instantaneous voltage and instantaneous current. It also determines SOC using the instantaneous current and voltage measurements. It can be noted that the Elite BMS can only be purchased with GBS battery cells.

Maybe you can add Cell-loggers (with modifications, ie a charger disable circuit) as a Level 1 option.

Just as reference the charge shuttling can be accomplished with capacitors or inductors. Inductors offer the most efficient and quickest balancing from what i remember, but like chef statemented these are complicated and almost no one is trying to design these BMSs

DaveAK
12 March 2011, 2108
Just as reference the charge shuttling can be accomplished with capacitors or inductors. Inductors offer the most efficient and quickest balancing from what i remember, but like chef statemented these are complicated and almost no one is trying to design these BMSs
I have one on my desk. :D

At least I have a TI evaluation board that does just that.

Nuts & Volts
12 March 2011, 2118
I have one on my desk. :D

At least I have a TI evaluation board that does just that.

Well of course and El Moto'er is doin it. We straight up BAMFs.

Is it capacitor based? I grand ideas once to do a inductor based setup, i don remember why i picked inductor over cap except for the reasons i stated above

chef
12 March 2011, 2124
Ah yes, need to shoehorn cell temps in one of the levels. Thanks for the info on Elite Power Solutions and the CellLog 8s.

DaveAK
12 March 2011, 2131
Well of course and El Moto'er is doin it. We straight up BAMFs.

Is it capacitor based? I grand ideas once to do a inductor based setup, i don remember why i picked inductor over cap except for the reasons i stated above
It uses inductors. And also monitors cell temps. I haven't played with it much yet, but I want to see what it takes to scale it up to the size we need.

Nuts & Volts
12 March 2011, 2202
It uses inductors. And also monitors cell temps. I haven't played with it much yet, but I want to see what it takes to scale it up to the size we need.

Dave you have all the cool toys! That was my dream BMS, but now I would rather save my money and rather save up and use cells that only require a Level 1 system.

By the way this level system could be awesome. If any new members come on we can point them to this thread and they can tell them to go for a level 11 BMS someday. Level 11 will work like a microwave, but instead of pushing the popcorn button you push the LiPo quick charge option or the max energy charge buttons.

Also I would suggest making the charge shuttling and bleed resistors should be on two different levels. The availability, complexity and cost between the two is pretty significant IMHO.

chef
12 March 2011, 2210
By the way this level system could be awesome. If any new members come on we can point them to this thread and they can tell them to go for a level 11 BMS someday. Level 11 will work like a microwave, but instead of pushing the popcorn button you push the LiPo quick charge option or the max energy charge buttons.

Also I would suggest making the charge shuttling and bleed resistors should be on two different levels. The availability, complexity and cost between the two is pretty significant IMHO.
A Level 11 popcorn button ? :D

Let me think about the charge shuttling vs shunting category. While the implementation & cost are very different between the two, the end goal is the same: to top-balance the cells. The levels are categorized based on overall goal and not so much implementation.

Nuts & Volts
12 March 2011, 2224
A Level 11 popcorn button ? :D

Let me think about the charge shuttling vs shunting category. While the implementation & cost are very different between the two, the end goal is the same: to top-balance the cells. The levels are categorized based on overall goal and not so much implementation.

Ok i follow and agree with your system.

Yes the popcorn button is a must. Ever notice that is the only preset button on the microwave that ever gets used?? clearly that's a sign that it needs to be on a BMS of the future

Skeezmour
12 March 2011, 2235
Wow I'm really not doing my job if our BMS doesn't even make the list. I'll work on this.

Nuts & Volts
12 March 2011, 2251
Wow I'm really not doing my job if our BMS doesn't even make the list. I'll work on this.

Apologizes sir. We are still in process of creating the list, I dont think anyone that has posted so far has experience with your BMS.

Skeezmour
12 March 2011, 2306
Hey no problem Nuts & Volts. We have probably been doing it longer than anyone else on the lists (not 100% sure but likely), going on 17 years. We are talking about new models geared more specifically to smaller ev's (bicycles, Elmotos, ect...). Of course cost is an issue that we are always working on but I'll apologize about cost before I'll compromise quality. Our gear is built right here in Washington State. Feel free to check out the current line of BMS/Chargers/Displays and let me know if you have any specific questions.

chef
13 March 2011, 0018
Links or it doesn't exist :p (to paraphrase Bruce)

In all seriousness, post or PM any info you can and I'll add it to the list. I don't claim to know of all the BMS's out there (I'm certain I don't). Just hoping to gather information so that we can all be better informed.

Skeezmour
13 March 2011, 0125
Here is a link to our MK3x8 BMS boards. I'm copying over the current discription from the page.
http://www.manzanitamicro.com/products?page=shop.product_details&flypage=flypage.tpl&product_id=54&category_id=22

<TABLE style="WIDTH: 100%" border=0><TBODY><TR><TD vAlign=top rowSpan=4 width="33%">
</TD><TD colSpan=2>MK3x8 Digital Lithium Regulator

</TD></TR><TR><TD vAlign=top width="33%" align=left></TD><TD vAlign=top></TD></TR><TR><TD colSpan=2>[/URL]</TD></TR><TR><TD colSpan=3></TD></TR><TR><TD>
</TD><TD colSpan=2>
<FORM id=addtocart_4d7c7eb69d065 class=addtocart_form method=post name=addtocart action=http://www.manzanitamicro.com/index.php>




</FORM>
</TD></TR><TR><TD colSpan=3></TD></TR><TR><TD colSpan=3><HR>The MK3x8 is an eight channel Lithium Ion Regulator like our Mk3x4 four channel regulator. With the change from through-hole to Surface Mount we have been able to decrease the per cell price and shrink the size from 8x4 inches to 6.9x2.4 inches with twice the channels. It has the ability to run on as few as 4 cells and any number up to 8. The MK3x8 dissipates 2.5 amps per channel speeding up the eqaulization process.


CUSTOMER REVIEW:

- Manzanita Micro gave us an awesome HUGE charger (PFC50) and provided a great BMS (using MK3x8s) for our battery pack. (The BMS just plugged in and worked perfectly. Nifty color-coded LEDs tell you exactly what is going on. Plug in your laptop if you want the detailed info on a cell level. Plugs right into the charger. Awesome.) - [URL="http://www.evahakansson.se/#home"]Eva Håkansson and the Electrocat (http://www.manzanitamicro.com/products?page=shop.ask&flypage=flypage.tpl&product_id=54&category_id=22)



KEY FEATURES
· Real time voltage monitoring of 4 to 8 lithium cells
· Real time temperature sensing of up to 8 external temp sensors
· Additional temperature sensor included on BMS module’s heat sink
· Small size is less than 1 inch thick and 7 inches long by 2.4 inches wide
· Quick automatic cell equalization and balancing with high and low voltage on board indicators and outputs to the charger
· Two high speed real-time warning lines which can be relay buffered for external use
· All BMS modules connect together using readily available RJ cable
· BMS easily connects to a PC using the DT USB adapter (Dongle/Terminator sold separately)
· Free Windows based scanner and command software available for download at www.manzanitamicro.com (http://www.manzanitamicro.com/) in the download section under MK3 Reg Support.
· All commands are easily entered and read in simple ASCII text
· Easy user adjustable min and max voltage parameters allow flexibility for various types of lithium cells from 1.75 to 5.5 volts per cell
· Each BMS board can bypass up to 2.5 amps per cell equating to fast charging and equalization of unbalanced cells
· Dual RJ reg bus ports for easy connection to the charger or other BMS units in a simple daisy chain fashion
· Self regulating thermal protection and feedback to Manzanita Micro Chargers
· Built-in active variable speed 12V DC fan control output on each BMS unit. The fan settings can be viewed and changed using the software found on our website
· Large heat spreader is totally isolated from the cells and is already threaded for easy mounting to a larger heat sink.
· Each unit can dissipate up to 110 watts
</TD></TR></TBODY></TABLE>

Coninsan
13 March 2011, 0348
You can also add the Chargery cell monitors V3.0 and 4.0 to the list as Level 1 BMS's these have rughly the same features as Cell-log.
http://www.chargery.com/cellMonitor.asp
http://www.chargery.com/cellSaver.asp

teddillard
13 March 2011, 0454
So, where does the balancing charger fit in with this BMS scenario? Let's say, for the sake of argument, a balancing charger on LiPo with a cell monitoring (Level 0?) system?

Coninsan
13 March 2011, 0654
So, where does the balancing charger fit in with this BMS scenario? Let's say, for the sake of argument, a balancing charger on LiPo with a cell monitoring (Level 0?) system?

Hmm technically this would be a Level 0, since it isn't a BMS at all, it's just a means of balance charging the pack, but it excibits behavior your would expect of a Level 2 BMS.

A level 2 charger? :)

Level 0 being a charger without the option to cutoff at HVW
Level 1 being one that can be shut off either via charger logic or a HVW
Level 2 being one that balances and regulates voltages accoirding to charge state just like an RC balance charger.

podolefsky
13 March 2011, 0911
A Level 11 popcorn button ? :D

Let me think about the charge shuttling vs shunting category. While the implementation & cost are very different between the two, the end goal is the same: to top-balance the cells. The levels are categorized based on overall goal and not so much implementation.

Great thread! This will be really useful.

A charge shuttling system can balance the cells at any point during the discharge cycle, not just to top balance during charging.

You might break up level 2 into subcategories like 2.1) what you have, 2.2) also does temperature, 2.3) actually includes temperature in the SOC calculation, etc.

Nuts & Volts
13 March 2011, 1008
Hmm technically this would be a Level 0, since it isn't a BMS at all, it's just a means of balance charging the pack, but it excibits behavior your would expect of a Level 2 BMS.

A level 2 charger? :)

Level 0 being a charger without the option to cutoff at HVW
Level 1 being one that can be shut off either via charger logic or a HVW
Level 2 being one that balances and regulates voltages accoirding to charge state just like an RC balance charger.

An RC charger actually has two settings. In regular charge mode it seems (this is what it looks like) that is simply charges and monitors the cells, stopping at HVC of one cell. It tries to charge to HVC of the pack but is stopped if cells are out of balance. Then you have balance charge mode which I am not sure how it works :( sorry. My guess is it pulls current from a few cells charges back up and then pulls more current until all cells are balanced.

chef
13 March 2011, 2338
Thanks Skeez and Coninsan for the additional BMS links.


So, where does the balancing charger fit in with this BMS scenario? Let's say, for the sake of argument, a balancing charger on LiPo with a cell monitoring (Level 0?) system?
Integrating the BMS & charger is the next logical step. This enables the BMS to precisely control the charging and reduces the risk of a communication failure between separate BMS and charger units. From the descriptions of the RC balancing chargers, they have taps to each battery terminal required for top balancing. The balancing charger alone isn't a complete BMS, but as part of a greater system it is a vital component. The RC units handle HVC & top balancing while other circuitry takes care of LVC. In the future there will likely be more integration with large format cell chargers & BMS's, eventually encompassing all the functions of a BMS as we now know it. Volumes will have to ramp up first to make this viable.

chef
13 March 2011, 2344
A charge shuttling system can balance the cells at any point during the discharge cycle, not just to top balance during charging.

You might break up level 2 into subcategories like 2.1) what you have, 2.2) also does temperature, 2.3) actually includes temperature in the SOC calculation, etc.
That's probably a good idea though I'm hesitant to make hard delineations for sub-features. That's because there may be BMS's that mix & match features (for instance 2.4 & 2.2 but not 2.3). There's already some blurring of the lines between L1 & L2. Maybe it would be clearer if I bulletized the features under each level?

Thanks for the clarification on charge shuttling. I'll update the post.

podolefsky
14 March 2011, 0935
Thanks Skeez and Coninsan for the additional BMS links.


Integrating the BMS & charger is the next logical step. This enables the BMS to precisely control the charging and reduces the risk of a communication failure between separate BMS and charger units. From the descriptions of the RC balancing chargers, they have taps to each battery terminal required for top balancing. The balancing charger alone isn't a complete BMS, but as part of a greater system it is a vital component. The RC units handle HVC & top balancing while other circuitry takes care of LVC. In the future there will likely be more integration with large format cell chargers & BMS's, eventually encompassing all the functions of a BMS as we now know it. Volumes will have to ramp up first to make this viable.

Elite Power Solutioons system has communication between BMS and charger. I guess this makes the charger part of BMS, so technically it has communication between the cell monitoring part of the BMS and the charging part.

podolefsky
14 March 2011, 0937
That's probably a good idea though I'm hesitant to make hard delineations for sub-features. That's because there may be BMS's that mix & match features (for instance 2.4 & 2.2 but not 2.3). There's already some blurring of the lines between L1 & L2. Maybe it would be clearer if I bulletized the features under each level?

Thanks for the clarification on charge shuttling. I'll update the post.

I agree, don't want to make it too complicated. I like the simple levels 0-3. Maybe then have a list of possible features and each system can have a check if it has that feature.

frodus
14 March 2011, 1133
like this:
http://liionbms.com/php/bms_options.php

podolefsky
14 March 2011, 1207
like this:
http://liionbms.com/php/bms_options.php

Yeah, something like that. I was thinking like this:

BMS_____________Elithion____EPS__ etc...

HVC________________x________x__
LVC________________x________x__
Balancing____________x________x_
Charger Ingration_____ ________x_
etc...
etc...
(we just keep adding features to the list here)

chef
15 March 2011, 2025
The Elithion folks did a nice job assembling that list. We could probably reference that and be done with it unless you guys want to continue updating this one.
On the flip side, they use some peculiar terminology that doesn't flow well IMHO.

frodus
15 March 2011, 2220
let me know and I can give the feedback to Davide.....

DRZ400
16 March 2011, 0628
I've used the Signalab V2 BMS. Works extremely well with my 48v20ah Headway pack, I have about 80 cycles so far and the cells all balance within 2-3 minutes of each other. Well made, simple (schematics on net), and inexpensive. On my next project I plan to use the Mini BMS system, very well engineered and I like that I can mount it on Calb cells.

chef
21 March 2011, 2322
let me know and I can give the feedback to Davide.....
The first thing I noticed is that the descriptions of each BMS category are peppered throughout the page at the top of each table. I had to page up & down dozens of times reading the descriptions trying to figure out what the differences were and remembering what was what. Not so easy when their terminology is less than intuitive. Revisiting the site a week later, I had to re-read the descriptions and learn the terminology all over again. An easy change would be to move the definitions together up towards the top of the page.
Upon re-review, there is a table at the top of their page that basically summarizes the categories. Some descriptions are ambiguous though... "Requests that battery be switched off".. is that charger HVC or controller LVC or both? That's one of the things I waded through the document for. Don't mean to knock their work. They've obviously spent alot of time gathering information, plotting graphs and putting it online and I'm appreciative of that.


DRZ400 : Thanks for the heads up on the Signalab. Do you have a link for it? A quick Google search turned up some posts on endless-sphere and other misc sites but nothing describing it in detail.

Skeezmour
01 April 2012, 1131
Just an update that we are about to start testing our next entry into the BMS market on my bike. It will be a 12 channel BMS with all the same features as our current MK3x8 with one exception. Much lower balancing current, this allows us to bring the costs WAY down. With the smaller AH packs that are used in e-bikes and elmotos we are confident that it will be a great fit. I have been testing for some time a lower disapation MK3x8 setup on my EXR1.0 32ah headway pack with great results so far. I will post more about it soon but I think the pricepoint should put as about the cheapest most feature rich and flexible BMS on the market. As always the products will be produced and supported right here in Washington State.

Updates soon.