BMS recommendation for high load DIY system

[boatsparky]

I am designing a lithium system for a boat. 12v 900ah bank of 3.7v cells (no, we cannot switch to 24v)
The difficulty is that I have a very high amperage draw windlass (160 amps continuous, short duration peak over 1000 amps)
I think the only option is a BMS that can drive an external contactor to take that load.
Does anyone have a recommendation on BMS? I prefer one that has alarm output as well.
Thanks

 

[Rocketman]

Look at Batrium. I am using it on my MotorHome- I wanted to keep the option to help boost/start my big diesel motor, so I wanted a contactor based unit.

I choose it because the software seemed simple and straightforward to me.

 

[boatsparky]

The Batrium products look good. Their terminology is a bit different it seems? They don't call it a BMS but I think it really is, "cellmate"

 

[Dooug]

What cells are you using? Is it possible to run more than one BMS? For example, 3 banks of 4s 304 AH cells, each with their own BMS capable of 2-300 sustained amps.

 

[boatsparky]

I have 54 GBS 100ah cells, will make into 12v bank(s). I am good with industrial power electrical type things, so a 500a contactor is familiar territory. Something about relying on massive FET's seems an unneeded risk? Maybe I am not understanding the benefits of that.

 

[400bird]

The Batrium products look good. Their terminology is a bit different it seems? They don't call it a BMS but I think it really is, "cellmate"

Cell mate is a legacy product that is still supported.
You'd want a Watchmon Core, shunt, plus a K9 for each parallel string (multiple if wired as separate strings, not parallel cells into one large battery)

 

[Quattrohead]

JBD make some very good BMS that have large contactors.

JBD Smart BMS 7~21S 8S 16S 20S 200A 300A Communicate with UART, Bluetooth or RS485 Function freeshipping - Jiabaida BMS

Jiabaida BMS JBD Smart BMS 7~21S 8S 16S 20S 200A Communicate with UART, Bluetooth or RS485 Function. High quality better service and favorable price with free shipping. Battery Management System for NMC/Li-ion Lifepo4 battery, 10+business for the protection boards manufaturing experiences.

jiabaida-bms.com

 

[boatsparky]

This is my first time designing a lithium system, so please excuse the terminology errors. I think I have 4s4p here. 16 100ah cells forming a 12v bank. The Batrium K-9 documentation says it can handle 16 cells, but I am unclear if they can serve this layout? There seems to be a few possibilities for how to configure 16 cells into a 12v battery. How is this one?

 

[boatsparky]

"JBD make some very good BMS that have large contactors."

When a BMS has large FET's like the JBD, AND contactor control, how does that work?
Would that leave the FET's as a redundant way to shut off the bank?

 

[MrSparkle]

AFAIK, all (?) BMS see 4p as one single cell.
(Unless there are some exceptions to that)
That means, in your case, you would only connect cell leads 1-2-3-4.

 

[boatsparky]

There is some disadvantage to not be able to see each cell status. This was covered in a prior thread I believe. How to weigh the value of having complete cell data over increased cost and complexity?

 

[DIYrich]

I have 54 GBS 100ah cells, will make into 12v bank(s).

52 cells will make 13 12v banks of 4s1p, or 3 4s3p plus 1 4s4p. With 4 200a BMS's, that will give 800 amps continuous and 1,250 amps surge.

 

[MrSparkle]

I do not know of a single BMS that could monitor or/and balance every cell of XsYp bank. I might lack knowledge on that part. Also, in permanent parallel config, cells are equalizing naturally by them selves. Monitoring individuals is still an other matter.
AFIAK the rout is then 4x batteries of 4s1p, means 4x BMS.

 

[Zwy]

This is my first time designing a lithium system, so please excuse the terminology errors. I think I have 4s4p here. 16 100ah cells forming a 12v bank. The Batrium K-9 documentation says it can handle 16 cells, but I am unclear if they can serve this layout? There seems to be a few possibilities for how to configure 16 cells into a 12v battery. How is this one?
View attachment 241308

If you are doing 1000A at 12V, well it would be much easier to just move to a higher voltage.

As for the K9, you would need one for each 12V cell series. Yes, you can parallel cells then build in series. But you would only have monitoring of each 4P so only 4 balance wires would be used.

Balancing in a K9 is passive at 0.75A. With 4P, this may or may not be a problem dependent upon the cells internal resistance.

 

[yabert]

I have 54 GBS 100ah cells, will make into 12v bank(s). I am good with industrial power electrical type things, so a 500a contactor is familiar territory. Something about relying on massive FET's seems an unneeded risk? Maybe I am not understanding the benefits of that.

I'm fully with you on that. Contactors win over fets on high current application.
After all it's why all EV battery have contactors and not fets.

I use JBD 300A BMS with contactor. Sadly, it for 7S-20S and you are building a 4S battery.
You can look at Heltec BMS who sell 4S contactor BMS.
Or you can try what Battery hookup advice. Use a regular 4S BMS and drive a contactor with it. Explanation here: https://batteryhookup.com/products/te-connectivity-ev200aaana-500a-0-900vdc
Of course the balance capacity will be to low, but if you don't mind to balance cells every few months/few years (depends of quality of cells) it's an easy and affordable solution.

 

[yabert]

There seems to be a few possibilities for how to configure 16 cells into a 12v battery. How is this one?
View attachment 241308

This is a 4S battery. Not a 16S battery despite using 16 cells to build it.
IMHO, nothing wrong to put cells in parallel to increase capacity.
OEM car maker do this in EV battery and no one tell them they are poor engineers.

 

[me3]

REQ BMS is designed for this. Just use a big Tyco contactor.

 

[HarryN]

Is there a reason to have it all under one BMS vs just build a few smaller units and parallel them.

For example, design it to have 100 - 200 amp-hrs for each battery and support 50 - 100 amp loads - each.

Put a breaker on each pack and run each to a common bus bar. You can repeat these in parallel as much as required.

This will be much more reliable as it provides redundancy and the ability to easily re-set the BMS by just flipping the breaker for that battery BMS.

You can even put in an AGM battery into the circuit if needed to act as a buffer / keeper so that the system does not go open circuit and destroy the alternator if the Li battery BMs all trip. Yes it will suffer a bit but they are only ~ $400, so cheap insurance.

Example:

 

[Brucey]

I am designing a lithium system for a boat. 12v 900ah bank of 3.7v cells (no, we cannot switch to 24v)
The difficulty is that I have a very high amperage draw windlass (160 amps continuous, short duration peak over 1000 amps)
I think the only option is a BMS that can drive an external contactor to take that load.
Does anyone have a recommendation on BMS? I prefer one that has alarm output as well.
Thanks

Commercially soon to be available would be a Lynx Smart BMS NG 1000A and sufficient Victron NG batteries. System supports multiple BMS units. The NG BMS contactor handles critical event disconnects, and can also be used to turn off battery power to the bus for maintenance etc

https://www.victronenergy.com/upload/documents/Datasheet-Lithium-NG-batteries-12,8V-25,6V-51,2V-EN.pdf

 

[boatsparky]

Is there a reason to have it all under one BMS vs just build a few smaller units and parallel them.

For example, design it to have 100 - 200 amp-hrs for each battery and support 50 - 100 amp loads - each.

Put a breaker on each pack and run each to a common bus bar. You can repeat these in parallel as much as required.

This will be much more reliable as it provides redundancy and the ability to easily re-set the BMS by just flipping the breaker for that battery BMS.

You can even put in an AGM battery into the circuit if needed to act as a buffer / keeper so that the system does not go open circuit and destroy the alternator if the Li battery BMs all trip. Yes it will suffer a bit but they are only ~ $400, so cheap insurance.

Example:

Good point on the Alternator current dump. I was planning to have the BMS disconnect the alternator field wire when a shutdown occurs, or ideally on a warning signal before shutdown.

 

[boatsparky]

I now understand BMS cannot monitor individual cells wired in parallel. Makes sense. Is there any known single BMS that can monitor 4 batteries of 4 cells? Eight BMS units will get expensive. I am unclear if multiple BMS can be daisy-chained together and operate a single contactor?

 

[Zwy]

I now understand BMS cannot monitor individual cells wired in parallel. Makes sense.

I do have to ask why this needs to remain 12V?

Is there any known single BMS that can monitor 4 batteries of 4 cells? 8Eight BMS units will get expensive. I am unclear if multiple BMS can be daisy-chained together and operate a single contactor?

Batrium CORE using 4 K9's with a shunt trip breaker.

It isn't as cheap as some options but any expansion down the road just add more K9's. I prefer the Batrium for monitoring my complete bank at cell level. You will want a Class T in between each battery.

Support with Batrium is there, but they want to charge for it. The online guides/documentation are a joke but most answers are in there somewhere. I think they made the documentation this way so you would be more willing to pay for support.

View attachment 242033

I recommend reading this thread regarding parallel batteries.

 

[boatsparky]

Okay thanks for the Batrium information. Despite the thin documentation the software looks great. I would need eight K9 units = 1,400 USD plus the Core @ 254. Total 1700 bucks The drawback with Batrium is the single point of failure (the Core unit).

Eight low-end Daly units would be about 500 USD. Might be preferred for the redundancy? One failure and can keep going. I am looking to see if they can support a single contactor.

 

[boatsparky]

Staying with 12v, because it's a boat with endless 12v gear on board, things quite expensive to swap out.

 

[DIYrich]

I now understand BMS cannot monitor individual cells wired in parallel. Makes sense. Is there any known single BMS that can monitor 4 batteries of 4 cells? Eight BMS units will get expensive. I am unclear if multiple BMS can be daisy-chained together and operate a single contactor?

You can build 4 batteries with for 200amp BMS's for about $600 for the BMS. It does require paralleling 3 or 4 cells for each battery, so you loose some resolution. The output of multiple BMS can be put in parallel. Just like putting rack batteries in parallel. That's what I would do to get 1000+amp surge. Note: three 100amp cells in parallel is similar to one 280-305amp cell.