I can't find a suitable BMS for a large LifePO4 prismatic 48v bank

[Becaris]

Here are my needs:

I plan to have four 200ah LifePO4 battery banks in parallel to get to 800 ah total. Each bank will need a BMS (48v 16s). I need to pull up to 100a from each of the banks at maximum load, so a draw of 400a, continuous, at times due to two electric pod propulsion motors. I don't want to pull more than 50% of the rated maximum on each BMS. Therefore, I need the BMS units rated for 200a, minimum. I will sail in cold climates, on occasion, so I need a low temperature cut off feature on the BMS units. I have a Victron system, and would like the BMS units to communicate with the Inverters. Here is the kicker, I don't want to spend nearly as much on the BMS units as it costs to buy the batteries they are protecting!

NOTE: To get the price of the BMS units down, If I had to, I would give up on the Victron communication, but not the rest of my requirements.

Each of my battery banks cost about $1,500 to build (without the BMS). All total, that's about $6,000 for the batteries.

I found the REC BMS system which fits all my needs, except for the price, which is atrocious at $1,100 per bank. By the time you get all the parts you need (slaves, master, several contractors, etc) I would spend $5,000 on the BMS system. That makes their BMS too expensive to protect $6,000 worth of batteries!

Are there any 48v 16s BMS units, rated to 200a, with low temp cut off, that anyone knows of that will do what I need and yet don't run $1,250 per bank? I would hope to spend $250 per BMS, but I may be dreaming. I certainly don't want to spend well over $1,000 per BMS.

Daly are at the right price, but the large ones have no low temp cut off (that I know of). Overkill are nice, and available at a great price, but max out at 100a. Batrium are even more expensive than REC (as are several others). QUCC are cheap, but have a single contactor built in, so it cuts off the batteries completely when it trips. That means, once it cuts off from, say, low power due to over draw, the BMS won't allow the batteries to charge while the contactor is tripped. Argh. Does anyone here have a different suggestion for a BMS that fits my needs? Help?

 

[snoobler]

You don't need a Batrium for each individual battery. A single Batrium can manage multiple batteries.


You need the CORE BMS kit with 32 Blockmons for 2 batteries and another 2 16X blockmons for the other two batteries. $1823.79 total for all 4 batteries, and it should get you what you want.

 

[Sanwizard]

The Heltec/JK BMS is rated for 200amps. If each bank will only pull 100a, why the need for 200?

 

[Becaris]

The Heltec/JK BMS is rated for 200amps. If each bank will only pull 100a, why the need for 200?

I understand that it isn't great to pull the maximum amps a BMS can handle. For safety and longevity, I want to pull 50%

 

[toms]

I second the Batrium recommendation. Remember that the BMS is the heart of the system - a more important component than the cells, don’t go cheap here especially in an offshore install.

 

[upnorthandpersonal]

I second the Heltec/JK BMS - there is even a 300A version - but that one comes in at over €400. The 200A version is half that.

95.99US $ |Smart Bms 1a/2a Active Balance Battery Protection Board 14s ~ 24s 100a 150a 200a 300a Phone App Lifepo4 Li-ion Lto 16s 20s - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Others on this forum and myself have had good results with it, but take that for whatever it's worth. The Batrium would be a perfectly fine option, and probably gives you less worries.

 

[Becaris]

I second the Heltec/JK BMS - there is even a 300A version - but that one comes in at over €400. The 200A version is half that.

95.99US $ |Smart Bms 1a/2a Active Balance Battery Protection Board 14s ~ 24s 100a 150a 200a 300a Phone App Lifepo4 Li-ion Lto 16s 20s - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Others on this forum and myself have had good results with it, but take that for whatever it's worth. The Batrium would be a perfectly fine option, and probably gives you less worries.

Does the Heltic/JK BMS have a low temperature sensor? (Sorry, I looked up the manual and it seems it does, so I answered my own question).

 

[Becaris]

You don't need a Batrium for each individual battery. A single Batrium can manage multiple batteries.

View attachment 53860
You need the CORE BMS kit with 32 Blockmons for 2 batteries and another 2 16X blockmons for the other two batteries. $1823.79 total for all 4 batteries, and it should get you what you want.

Thanks for the info on the Batrium. That brings it down to a somewhat better price at about $450 per battery. I will look into that one a little deeper.

 

[jtvt]

I use a batrium on two strings (560ah) and will be upgrading to 4 strings total (1120ah). I already have the additional blockmons and my second set of batteries are at customs. I use a shunt trip breaker, but you could use one or more contactors. There is some victron integration, but not sure how much. I don't use victron.

One thing about Batrium is they answer email. Every email I've ever sent has been responded to in a day. We're on different time zones. This sealed the deal for me. It also has a mature interface (just windows) and substantial documentation. It's not cheap chinese junk that looks like it was soldered together by a 6 yr old.

 

[Becaris]

I use a batrium on two strings (560ah) and will be upgrading to 4 strings total (1120ah). I already have the additional blockmons and my second set of batteries are at customs. I use a shunt trip breaker, but you could use one or more contactors. There is some victron integration, but not sure how much. I don't use victron.

One thing about Batrium is they answer email. Every email I've ever sent has been responded to in a day. We're on different time zones. This sealed the deal for me. It also has a mature interface (just windows) and substantial documentation. It's not cheap chinese junk that looks like it was soldered together by a 6 yr old.

So, from what you are saying, I have to add in the cost of contactors or shunt trips. I suppose I could combine two strings and use a 400a shunt trip, but that still means 2, or combine all four strings and go with one 800a shunt trip. There goes another added cost to the Batrium BMS system.

 

[OffGridInTheCity]

I've been running Batrium Watchmon4 (WM4) + Expansion for a couple of years now. Its important to understand that Watchmon4 is a monitor of daisy-chained (networked) external 'mons' - e.g. blockmons, longmons, etc - all do the same thing but have different physical design for easy hookup to leaf cells or other stuff. "Longmons" are the general purpose mon.

For example, I have 84 packs of 260ah each. Each one has a longmon on it - you simply connect + and - to the + and - of the pack. I have 6 'batteries' of 14s packs in parallel - but that's 84 packs (and 84 longmons). The longmons are connected by cables you buy to form a network back to the Watchmon.

You simply tell the Watchmon software that you have X longmons (84 in my case) with Y 'nominal' battery (14 in my case). You can do any combination.

Each longmon is up to 2a balance (very hefty) and you can do up to about 500ah 'packs' and balance within 'days'.

>I plan to have four 200ah LifePO4 battery banks in parallel to get to 800 ah total. Each bank will need a BMS (48v 16s).
If you put 1 longmon on each LifePo4 'brick' - that would be 4 x 16 = 64 longmons. Perfectly reasonable for Batrium. You could save money by doing 2 sets of 16s2p - that would only require 32 longmons and they can handle 400a per 'cell'. You would X longmons with '16' as your nominal number instead of 14 like mine.

Finally - Batrium WM4 does NOT do anything about battery load. Rather it monitors... and can trigger shunt-trips. For example, I use a SACE S3 400a shunt-trip wired to the Batrium expansion board (e.g. a bunch of user programmible relays).

For example, in my cargo trailer I have 14s (14 longmons) and here's the CellMon (longmon) settings page:


where I tell it to fire the shunt-trip if any pack goes <3.30v or above 4.17v. Bypass Volt = 4.15 will turn on balancing. There's also hi/low temps. There's a TON of settings and you can fire many external actions (besides a simple shunt-trip) if you want to get into it

And then here's the main monitor page - each BLUE bar is a longmon reporting it's details.


And here's an example of my powerwall - with 84 packs (84 longmons) - just to give you a sense of how it looks:

 

[snoobler]

So, from what you are saying, I have to add in the cost of contactors or shunt trips. I suppose I could combine two strings and use a 400a shunt trip, but that still means 2, or combine all four strings and go with one 800a shunt trip. There goes another added cost to the Batrium BMS system.

No. Batrium has full CAN communication with a Victron GX device. It can command them directly vs. opening a contactor.

 

[jtvt]

So, from what you are saying, I have to add in the cost of contactors or shunt trips. I suppose I could combine two strings and use a 400a shunt trip, but that still means 2, or combine all four strings and go with one 800a shunt trip. There goes another added cost to the Batrium BMS system.

I think you have a design question. If you have contactors on each string and shutdown a string for whatever reason and still use the other strings, your strings will then not be balanced. If you add back that string and voltages are not close, you may have fireworks. If you add back the string and the soc is drastically different than the other strings, you will either have that single string dropping out again or the other three strings dropping out on cell LVCO and cell HVCO. Certainly you can fix these problems, but that's a pain. The flip side is that if one string drops, then you still have power. If the remaining strings can power the loads, then all is good. If they can't power the loads, you have a bigger problems perhaps even for the equipment you are trying to power.

I opted for a single shunt trip breaker. Reason being that properly balanced cells and properly configured equipment should never get close to cell LVCO and HVCO. So far, my two strings have been balanced well. The batrium seems to do a good job. The batteries are all located in one place. If a cell has a low or high temp cut out, then good chance the other cells are soon to follow. So might as well as shutdown the entire bank.

In terms of contactor vs shunt trip: The shunt trip doesn't use juice and contactors can weld themselves. If either fires, I have to visit the battery. If I have to visit the battery, I can manually reset the shunt trip.

 

[OffGridInTheCity]

Agree with @jtvt comments. I have a master ABB SACE S3 400a shunt-trip for the overall battery bank - wired to isolate the battery from the overall system - e.g. when it's off there is absolutely *no* power coming from the battery.

I went with with ebay ABB SACE shunt-trips as I've seen them used by many for larger powerwalls and they are affordable and come in all ranges of amps up to 600a. For example, here's a 100a model w/shunt-trip. https://www.ebay.com/itm/272871269263?hash=item3f8865238f:g:AC4AAOSwICpaBbV5
If you go SACE you have to scour the descriptions for 1) that they have shunt-trip and 2) the shunt-trip voltage is what you want - 24vdc is good as you can tap you're battery bank for momentary power to trip it. For example - from the listing above notice this pic showing 24vdc coil.



Some have 110vac coils - not so good

FYI: One thing that was never clear to me is the term 'pulse' of power and maybe it will help to spell-it-out. Shunt-trips take a 'pulse' of power (e.g. 24v in this case) and then once tripped - the coil stops pulling power - e.g. it turns itself off after doing it's job.

At the risk of TMI: Another tidbit is that 3 pool shunt-trips can be used for the PV array power as well. After you use 2 poles for + and - of the battery bank you have a 3rd pole left over - some use it as a main disconnect to incoming PV power... so that all sources of incoming power are 'off' as a response to the trip event.

 

[lance]

No. Batrium has full CAN communication with a Victron GX device. It can command them directly vs. opening a contactor.

Hey Snoobler: Searching threads for Batrium communication with Victron, hoping to find someone who's documented their successfully made communication cables from there Watchmon to their Cerbo (or other GX device) AND their Multiplus. I'm just getting started trying to sort this out but, am finding Batrium's direction to be lacking directness/clarity. And while Victron acknowledges their eqpt WILL communicate with other mfr.s of BMS, they don't get into too much detail. I'll continue my search here but, thought you might be able to save me some time.

 

[curiouscarbon]

Hey Snoobler: Searching threads for Batrium communication with Victron, hoping to find someone who's documented their successfully made communication cables from there Watchmon to their Cerbo (or other GX device) AND their Multiplus. I'm just getting started trying to sort this out but, am finding Batrium's direction to be lacking directness/clarity. And while Victron acknowledges their eqpt WILL communicate with other mfr.s of BMS, they don't get into too much detail. I'll continue my search here but, thought you might be able to save me some time.

fyi, snoobler has not visited for a while.

all the same, best of luck with your system integration

 

[lance]

fyi, snoobler has not visited for a while.

all the same, best of luck with your system integration

GTK! Thank you....

 

[magic8192]

You can discuss your battery setup via email with batrium. info@batrium.com

 

[Dzl]

Hey Snoobler: Searching threads for Batrium communication with Victron, hoping to find someone who's documented their successfully made communication cables from there Watchmon to their Cerbo (or other GX device) AND their Multiplus. I'm just getting started trying to sort this out but, am finding Batrium's direction to be lacking directness/clarity. And while Victron acknowledges their eqpt WILL communicate with other mfr.s of BMS, they don't get into too much detail. I'll continue my search here but, thought you might be able to save me some time.

fyi, snoobler has not visited for a while.

I would ask @sunshine_eggo, they know Victron pretty well and maybe Batrium, I suspect they can shed some light on the topic.

 

[sunshine_eggo]

I'm behind the curve on Batrium deployment at the moment.

Start here:

Batrium

support.batrium.com