Suggestions (please) for BMS for large 8s battery bank

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prepared1

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I need help. Been trying to make a decision on what BMS to use for monitoring and charging a bank of (26) 8s Li-NMC prismatic modules. They are equipped with nice stainless bolts for battery (-) (+). This will be a nominal 48 volt bank, charged to about 60v. So about 46 kWh. I don't do programming, so any options that require Linux or similar are out for me.

The modules are in like new condition, and will be used with existing Victron inverters. Beyond that, no decisions are made. Until our solar array is installed, we will use the grid connection to charge, or generators.

I've tried contacting companies like Orion, Evolve Electrics, Energus, etc, mostly with the same result; lack of people to speak with, or they want you to send an email. Then I don't hear back from them. I did get a quick reply from Batrium, which I am going to follow up on.

After reading what seems like a million posts about Daly, Chargery, ANT, and other Chinese units, I don't see a consensus on what would be the most reliable. My thought was to set this up as a 16s system, by putting each pair of 8s in series first. Would it make sense to just buy a quality BMS for each battery pair? That would be 13 BMS. The price is not my concern, because Batrium Orion, REC and others cost a lot. I want to be able to set the basic parameters for a safe operation, and be able to view that info on a dedicated screen. I don't care about Bluetooth, but would use it if needed.

I have a couple BMS from Battery Hookup that we are getting ready to set up for a friend for a small powerwall, about 5.5kwh. Those are 12s units. Would the 16s versions be a good candidate for the larger system?

Please, any suggestions would be appreciated.
 

OffGridInTheCity

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You didn't list Batrium (www.batrium.com) - e.g. the cadillac of BMSs - for large batteries and made for more exceptional reliability as far as I can tell. Watchmon 4 + longmons would work.

I have 2 x Batriums - DIY powerwall - 81kwh / over 2 years and cargo trailer - 14kwh / more recent.

I also have 6 x Chargery(s).... but Chargery(s) are hit-miss for me as 50% failed but.... 50% work great on smaller batteries.
 
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prepared1

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OGITC: I think you just missed the mention of Batrium. They did get back to me, today. Maxine said they have a new product coming out in about 30 days that would be ideal for my set-up. It is in testing right now. She also linked a bunch of videos for me to watch. I'm impressed with the quick response.

I have read your posts previously with a lot of interest. What you are doing seems to be along the same lines as what I'm trying to do. Today, I spent a lot of time with a solar installer who is willing to come work with me to get the panels up, and the inverters wired. I'm anxious to get the BMS figured out so we are ready to move on that soon.

I'd be interested to hear your thoughts on how easy or difficult the Batrium was to install, and get working properly.

Thanks!
 

OffGridInTheCity

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OGITC: I think you just missed the mention of Batrium.
You're right - sorry about that :)

I'd be interested to hear your thoughts on how easy or difficult the Batrium was to install, and get working properly.

Thanks!
It was as easy as any BMS to connect longmons to the packs (simple twist ties + quick solders of + and - wires). Watchmon needs some setup - e.g. computer work. The external (in my case SACE) shunt-trip required some hookup.

I think I've lost my beginner's edge here... so to me it seems easy (now) but not so much before I actually did it - if that makes sense.

@daromer and @AveRageJoe and @hbpowerwall and @LithiumSolar all have good youtubes on Watchmon4 + Longmon installs and turn-on.

Happy to answer anything specific (that I can) or help if you decide to go that route.
 

floydR

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They did get back to me, today. Maxine said they have a new product coming out in about 30 days that would be ideal for my set-up. It is in testing right now. She also linked a bunch of videos for me to watch. I'm impressed with the quick response.
Would the new product be the WatchMon-CORE with CellMate-K9 for Share balancing wiring (Coming Soon)? no longmons to set up?
later floyd
I am looking at the CellMate-K9 myself.
 
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prepared1

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FloydR....why yes!

I got another email from Batrium today. The new CellMateK9 is in pre-order status. I'll watch that video today. Last night I watched some videos about BlockMons, which look interesting.

The thing that somewhat surprises me is that the existing systems worked up to 15s, but not 16s. In my limited experience, there are quite a few 16s batteries floating around for sale. I have many. On their site, they discuss making it easier for people to use the wire looms that come on many automotive cells, and avoid having to wire them yourself. With my admittedly limited knowledge, I assume they refer to the balance wires on many of those modules. (You mentioned that ) Nearly all the prismatic modules I have purchased have those, so it sounds like a great idea.

One question I have never seen answered is this: if you have 2 modules you intend to series together, whether they are 6s, 7s, 8s, etc...can you put an independent BMS on each module, IE on (2) 8s, and then connect them in series? Meaning, a BMS from another source, not Batrium. Just curious..

OGITC: Thanks for your comments. They are always informative and welcome!

Danka!
 

OffGridInTheCity

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One question I have never seen answered is this: if you have 2 modules you intend to series together, whether they are 6s, 7s, 8s, etc...can you put an independent BMS on each module, IE on (2) 8s, and then connect them in series? Meaning, a BMS from another source, not Batrium. Just curious..
My Opinion: Yes you can - for example any of these pre-built batteries such as SOK (just reviewed by @LithiumSolar) or Battle Born or X - each have their own BMS and many hook them in series or parallel... to a degree. Some of them give a 'limit' recommendation - but like you I'm not sure how they arrive at these 'limits'.

Now - some downsides....
Series - Think about 4 x 12v batteries in series for 48v. If just 1 BMS goes 'out' the whole battery will go out. It may not be easy to manually discover which one is bad - you'd have to check each battery in series ... maybe even take them out of their enclosure.
Parallel - If you have 3 batteries/BMSs in parallel at 50a each and you pull 120a... then if one BMS fails it will cascade trip the other 2 BMSs. And various combinations like that. Again, you may need to deal with each individual battery to find out what's wrong.

I think the allure of 1 BMS is that you have the 'whole picture'... and if you go with multiple independent BMSs, especially cheaper ones complicate things. So hooking 4 x Battle Borns in series is probably a bet I would take - but hooking 4 batteries in series with unknown / cheap BMS not so much :)

One of the unique/cool things about Batrium Watchmon 4 +Xmons - you can add *many* 'batteries' over time but yet still have 1 overall BMS. and unlike WM5 its not lithium-ion centric (e.g. 15s limit per battery). I don't think WM4 has any 's' limitation - you can put in any multiple you want.
 
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daromer

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I dont recomment to series any battery that isnt

1. Built for from factory and they clearly states they have warranty for it!!
2. You have a data cable that connects the 2 bms systems together (Valence among many other LiFePo4 manufactures do it like this)

Samt goes with paralell to be honest. As OGTC said in last post.
 

ajw22

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My Opinion: Yes you can - for example any of these pre-built batteries such as SOK (just reviewed by @LithiumSolar) or Battle Born or X - each have their own BMS and many hook them in series or parallel... to a degree. Some of them give a 'limit' recommendation - but like you I'm not sure how they arrive at these 'limits'.

"to a degree" indeed.
The problem is that the BMSs don't talk to each other and can act individually.
So when one BMS in the series decides to interrupt the whole circuit, the components of that BMS (primarily the MOSFETs) has to be able to handle the voltage of the whole circuit, with a generous safety margin to account for any potential voltage spike that might occur when slamming a circuit shut.
The "voltage spike" will heavily depend on what kind of load you have. Almost no spike if you have purely resistive loads, huge spike if you have inductive loads like motors.
Rather risky, unless you have the datasheet or know the internals of the BMS.

eg.
My 14S "Smart BMS with bluetooth" come equipped with max 80V MOSFETs, so using 2 BMS in series to cover a 28S system (max 120V) would kill the MOSFET at the first STOP event for sure.
 

floydR

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The lack of information is what is stopping me from ordering such as why would you need multiple CellMate-K9's if you are using a shared wiring loom? Guess I should email Batruim to find out.
later floyd
 

prepared1

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floydR: I took that to mean the loom that comes on each individual module, since their description pertained (primarily) to automotive modules. But, the same would likely apply to ESS modules. Somewhere in their description it talked about the limited current carrying capability of the particular sized wire that is on the modules. In my case, I could need multiple expansion boards. I watched LithiumSolar videos on his Batrium setup, which were VERY informative, if you haven't seen them.

I could easily be wrong, and would like to know. But, when I detailed to Batrium what I was looking to do, they immediately recommended that I wait a month, and get the new system.

On the other topic, that of using a BMS for each modules, and then series connecting them, there does seem to be a lot of potential issues. I was more curious than actually wanting to attempt that.

Thank you everyone!
 

floydR

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I see that the Batrium WatchMon-CORE kit +CellMate-k9 is now listed on the Batrium web site.

Later floyd
 

prepared1

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floydR: Yes, I saw that last night. I suspect I will be placing an order, as soon as I figure out exactly what I need. One of the videos I watched mentioned that they had a special wire loom available for people who wished to place the equipment in a more remote location. Hope I'm not confusing Batrium with another system.....

Not sure if that would be needed anyway with this new option. Have to read up more.
 

prepared1

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While I was looking at the Batrium store site today, prices jumped 10%. Wow.

Still trying to figure out the whole system, and how you would hook up a large grouping of modules.
 

OffGridInTheCity

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On the surface, it looks like WatchMon-CORE replaces WatchMon4 - https://www.batrium.com/collections/kits/products/watchmoncore (I have 2 different WM4s + Expansion + Longmons). I'll be interested to see if you can drop in a CORE and continue to use the pre-existing longmon infrastructure.

Looks like the "CellMate-k9" https://support.batrium.com/article/351-cellmate-k9 is an alternative to individual longmons....
  • cell monitoring from 0.50V to 5.50v with 0.001 resolution
  • configurable to suit LiFePO4, Lithium-Ion or custom chemistry
  • Auto-Level (balancing) function at 500mA with activity LED on each cell **This is interesting - WM4 software has this feature for Longmons.
  • Capable of 6 Ah/day balancing adjustment for each cell
Longmon - https://support.batrium.com/article/123-longmon has
  • Battery range 2.2V to 5.4V.
  • Bypass current 0A to 2A (typically 1A). **Longmons 4x more amps for balance?
  • Over-temperature protection.
  • Over-voltage protection up to ±20V.
While I was looking at the Batrium store site today, prices jumped 10%. Wow.
Batrium's not cheap and like all things - has a few issues - so I have mixed feelings - but (for me) it really is a great solution for an 84 pack powewall with plans for 42 more. It really eases powerwall pack additions over time.

Still trying to figure out the whole system, and how you would hook up a large grouping of modules.
If Core = 4 - then I hope the base cell monitoring option with XMons will remains the same. IF you can still do Mons, then mons just hook + and - wires to + and - on each pack. You don't have to - but its convenient to mount longmons at the physical pack/cell to get individual pack temps.
 
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