Confused on which Batrium hardware is needed for my setup

My Setup: I have 64 LiFeP04 cells coming my way.

I'm very confused on which Batrium products I would need to support my setup. I think I'm confused because in their BMS kits, nowhere does it say what products I would need for a 16S4P. I do not have any existing Batrium products so I'm starting fresh. Can anyone point me in the right direction on which products I would need from them for my setup?

Much appreciated

Watchmon CORE and 4 K9's would be preferred for individual cell monitoring. Don't understand why you would want 14S, but you may have certain reasons. You can run 3S to 16S with the K9. https://www.batrium.com/collections/kits/products/watchmon-core-k9

Some will parallel 2 cells in a pack, for what another K9 costs, I don't really see a reason why to parallel cells. For my system, I originally ordered 2 K9's for 2 16S packs but now plan on adding another pack so I only need to add another K9. Send Batrium an email for further questions.

I will not go 14s, I erased that part. Agree it doesn't make sense for the number of batteries I have.

So essentially I need four K9's if I want four groups of 16s? Is there anything else? I'm confused about the longmons and if those are necessary.

Appreciate the help

No need for Longmons, the K9 does the cell monitoring. The CORE is the brains of the unit, the K9's are slaves. 4 K9's for 4 groups of 16S.

Watch Lithium Solar on CORE with K9 install.

You can use either the K9s or blockmons/longmons. Both setups will work. The k9s replace the need for blockmons or longmons. I have 64 cells configured as 4 parallel strings of 16 cells with blockmons. I don't think there is necessarily a better option between K9s versus Blockmons. IIRC blockmons have more balance capability. But there is a blockmon attached to each cell. If cell posts are short or space is an issue that might be a problem. Blockmons are daisy chained back to the core. Maybe more parts to fail, but less wire involved than the K9s. IMO a toss up with maybe balance capability being the main decider.

jtvt said:

You can use either the K9s or blockmons/longmons. Both setups will work. The k9s replace the need for blockmons or longmons. I have 64 cells configured as 4 parallel strings of 16 cells with blockmons. I don't think there is necessarily a better option between K9s versus Blockmons. IIRC blockmons have more balance capability. But there is a blockmon attached to each cell. If cell posts are short or space is an issue that might be a problem. Blockmons are daisy chained back to the core. Maybe more parts to fail, but less wire involved than the K9s. IMO a toss up with maybe balance capability being the main decider.

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Thank you for the share. I think I'll just go with the k9s, I don't need that much more balancing capacity and these are brand new cells so they should be in good shape for a while.

Just out of curiosity...It's looking to be a bit over $1k if I go with Batrium (16Sx4 = 4k9's). I like them because their BMS has a lot of open source features and also integrates with my Inverter/charger setup. But it's a lot of money and it kind of seems like a homebrew setup they have going. I also don't love that I will need separate hardware to cut off the batteries if they reach a critical state (over voltage, temper..etc). Other BMS's have that functionality built in.

What do you like about them that makes you pay a premium?

My decision was based upon ease of expansion, individual cell monitoring, high discharge ability, software and flexibility.

I can easily add another bank with the addition of a K9. That's a big deal, in the future there is always the possibility I will want to expand, not only in battery capacity but PV size and number of inverters.

One can parallel cells or have individual cell monitoring. For 64 cells as an example, you can have every cell on the screen and every cell is monitored.

Instead of relying on mosfets in the BMS, the use of a shunt trip is much safer. Highly unlikely the Batrium will fail compared to a mosfet based BMS. This also allows high discharge capacity thru a shunt trip breaker, something not so easily done with a mosfet based BMS. High discharge rates won't heat up the BMS and cause shutdown, disconnect or mosfet failure. A contactor based BMS is similar, some draw current to hold in the contactor and there is an elevated risk of a contactor welding internally compared to use of a shunt trip breaker rated for DC.

Software and interface allow for customization, ease of settings. Relay board(s) allow greater control for outside devices.

Drawbacks? Sure, need for a shunt trip breaker such as the ABB. Used shunt trip breakers aren't as cheap either, one could buy in the past for $100, now you see $200. It's a more complex system in some respects but also simple. The complexity is in the software, the hardware is simple enough. An advantage of having multiple K9's is if one K9 fails, one can easily change the daisy chain to get power back. Is this plug and play? No, but that also allows greater flexibility when building a system.

Thank you. Your explanation and others I have read is helping me lean towards Batrium still.

Zwy said:

the use of a shunt trip is much safer

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Do you have any recommendations for Shunt Trip breakers? I know you mentinoed ABB, Can these breakers be turned back on remotely or does it require manual human intervention?

I would also assume I need a breakers on my MPPT Controller as if all the batteries are cut I need to cut solar to my charge controller. I have a Victron Charge Controller, Inverter and VenusOS...I know batrium can communicate with them but in the scenario of all batteries being disconnected I believe I would still need to cut solar to the charge controller.

Much appreciated.

hummmingbear said:

Thank you. Your explanation and others I have read is helping me lean towards Batrium still.

Do you have any recommendations for Shunt Trip breakers? I know you mentinoed ABB, Can these breakers be turned back on remotely or does it require manual human intervention?

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I used the ABB, found easily on ebay. Looked at many different ones, finding DC rated in higher amp ratings is not such as easy task. While the shunt trip will remotely trip the breaker, I'm unaware of one that will reset remotely. First, that would defeat the purpose, the breaker trip would be due to a failure in the battery bank and a fault the Batrium sees. That would need to be corrected first. The shunt trip breaker in this application is not really being used for excessive amperage but rather as a switch to cut off the battery bank. I still have Class T fuses on the cables after a busbar for excessive amps.

hummmingbear said:

I would also assume I need a breakers on my MPPT Controller as if all the batteries are cut I need to cut solar to my charge controller. I have a Victron Charge Controller, Inverter and VenusOS...I know batrium can communicate with them but in the scenario of all batteries being disconnected I believe I would still need to cut solar to the charge controller.

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Batrium supports canbus and many different inverters and CC's as you have found. I would think the CC's would shut down with the right settings, no need for a manual disconnect. Here is Victron Venus. https://support.batrium.com/article/110-how-to-control-victron-gx-with-watchmon


If you really want a manual disconnect like a small shunt trip breaker to CC's, Lithium Solar had a video where he used a Batrium expansion board containing 3 relays to cut off the charge controllers when his battery bank was below freezing. This could be applied to the Batrium where if the shunt trip breaker is tripped, the Batrium can activate a relay which in turn can trip a small shunt trip breaker from PV array. There are many options by simply adding an expansion board, that is what makes the Batrium versatile for a DIY'er.

hummmingbear said:

Much appreciated.

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You're welcome.

Zwy said:

While the shunt trip will remotely trip the breaker, I'm unaware of one that will reset remotely. First, that would defeat the purpose, the breaker trip would be due to a failure in the battery bank and a fault the Batrium sees. That would need to be corrected first.

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I have since let this idea go, for those reasons and others. Makes sense just to have one Shunt Trip for the whole battery and to manually re-enable it if a fault occurs.

Zwy said:

Batrium supports canbus and many different inverters and CC's as you have found. I would think the CC's would shut down with the right settings, no need for a manual disconnect. Here is Victron Venus. https://support.batrium.com/article/110-how-to-control-victron-gx-with-watchmon

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I know it can cut/alter the charging current which makes sense in many scenarios, but in a scenario where the Shunt Trip is activated and battery is cut, all connection to the batteries is lost, including the charge controllers, meaning you can't send any information to them at that point. My understanding is that it would be very bad to have solar input to the charge controller with no connection to a battery.

I'll checkout lithium solar's video on setting that up. Using some high-powered relay's on the solar input of the CC might also suffice. And again, thanks for the help. This forum has been invaluable.

I use Batrium Bms on my MotorHome.

If the battery goes critical I use a Kilovac contactor (relay) to cut power EV200AAANA (along with a Rec-pre-charge top recharge the inverter for startup).I have it setup so once the battery is no longer critical it will restart.

I went with Batrium because the user interface made sense to me and it would allow the boost function on my MotorHome to remain active (using the lithium battery to help the chassis battery start the big diesel motor if the chassis battery is having problems).

As far as your question about the SCC being cut-off from the battery- I had it happen.
I had battery acid drip onto the Batrium bms (hint - don’t let that happen…) I cleaned it up the best I could and it was working fine. A week later I was camping and the bms shut off the contactor and then a bit later turned it back on. So the SCC were disconnected from the batteries.

Upon researching what was going on, the Batrium was losing connection to the Shuntmon - thus went critical I think some battery acid finally corroded a connection inside the bms.

The SCC’s didn’t have a problem with the battery getting turned on -off-on-off-on. I think in my case I had some loads running (fans, lights, inverter, etc) so they took up any problems. The solar was able to tun everything at that time.

Good luck with all your decisions!

hummmingbear said:

Thank you for the share. I think I'll just go with the k9s, I don't need that much more balancing capacity and these are brand new cells so they should be in good shape for a while.

Just out of curiosity...It's looking to be a bit over $1k if I go with Batrium (16Sx4 = 4k9's). I like them because their BMS has a lot of open source features and also integrates with my Inverter/charger setup. But it's a lot of money and it kind of seems like a homebrew setup they have going. I also don't love that I will need separate hardware to cut off the batteries if they reach a critical state (over voltage, temper..etc). Other BMS's have that functionality built in.

What do you like about them that makes you pay a premium?

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I've had good luck with the support. Product is decent quality. There is a decent interface which is unfortunately just windows. I have a laptop setup at the battery and also a laptop in the house both monitoring the system. I also have Teamviewer setup (Batrium's recommendation) on the battery laptop, so I can tweak things via my phone, etc. Works fine. I'd rather an app, but that is all there is now. Batrium has talked about html interfaces and apps, but nothing yet and seems like they have been in the works for quite a while now. May never happen. I've got the expansion board and have shunt trip wired in. Shunt trip because I figured I would have to visit the battery if there was an event. I'm off grid. There really is no scenario where I would get a critical fault and not have to visit the battery. I'm currently wiring in some fans using relays on the Batrium. Lots of options with the Batrium and lots of possible controls. I don't have any integration with my inverters or charge controllers yet. It doesn't appear to be critical. The window for which the inverters and charge controllers operate is well within the cutoff limits set up in the BMS. Some equipment can't handle a battery disconnect, but some are fine with it.

I like the system disconnect being separate from the BMS. If your disconnect fries in an all in one bms unit (like the QUUC one where the contactor fried for the Offgrid Garage guy), you no longer have a working bms. Lead time on some BMS is long while you can get a new contactor or shunt trip overnight. All the chinese bms I looked at appear to be soldered together by 6 yr olds. Some have multiple leads going into one crimp. Probably fine for a small system. But I'm in it for the long haul with thousands of dollars in batteries. I'm didn't want to skimp on the BMS.

Rocketman said:

If the battery goes critical I use a Kilovac contactor (relay) to cut power EV200AAANA (along with a Rec-pre-charge top recharge the inverter for startup).I have it setup so once the battery is no longer critical it will restart.

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I'm looking at the datasheet for the contactor/relay and want to make sure I understand it right. You have it between either your Positive or Negative lead to the battery (but not both), and when you remove power from the aux wires of the relay opens and cuts the connection between your lead?

This also means you are powering your BMS directly from the batteries before your shunt, or another source, so that it can still operate and send power back to the relay to make the connection again?

Rocketman said:

Good luck with all your decisions!

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Haha...yes, there are many to make. It's fun though, right??? I'll keep reminding myself.

Thank you for this response. All this advice is helpful and is confirming a lot of thoughts I've already had about the setup. I'm also off-grid, but there are occasions where I might be gone for a month or two and it's nice to have things automated, hence a shutoff that can be turned back on by the BMS. I agree with you that I'd like the Breaker/Relay/Shutoff to be separate from the BMS. The more I look into it the "all in one" BMS aren't that great.

I tend to over-engineer things and I know that, but I also like it. Complex and Complicated are very different. I don't mind some complexity if it makes sense and works.

jtvt said:

All the chinese bms I looked at appear to be soldered together by 6 yr olds. Some have multiple leads going into one crimp. Probably fine for a small system. But I'm in it for the long haul with thousands of dollars in batteries. I'm didn't want to skimp on the BMS.

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Ahaha...yeah. I want quality builds as well. Living off grid you really learn to *try* and do it right the first time. I don't mind an initial investment early on if it means longterm stability and better life for the batteries.

Hummingbear - the flexibility of the Batrium means you can wire it up in different ways. The way I choose:
My Contactor on the positive wire. My positive comes off the cells - goes to a class T - then to the contactor - then to my rig. I don’t think it would be good to have the contactor on the negative wire. (Don’t know where I got that idea???).
You are correct that I am powering the BMS & Shuntmon before the cutoff contactor. That’s the way I wanted my system. (Others may have different wants and needs).

If you want to see my build and thoughts:

hummmingbear said:

Complex and Complicated are very different. I don't mind some complexity if it makes sense and works.

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That's one thing with LFP versus Lead acid. Lead acid is so much simpler. This doesn't matter to us as system designers/builders, but it's a problem if we need someone else to take whatever steps are necessary to turn a system back on. When I had lead acid, I wrote a manual with steps on what to do in various situations such as "no power in the house". I'm putting together the same for my LFP system and it's way more complicated.

Off grid has the one issue where if your battery is diconnected, you typically don't have networking. There is nothing you can do remotely to fix an issue if you have no networking to your bms or other devices. I've heard of some people with secondary lead acid batteries that power critical loads. I've been thinking about looking into a UPS for this, but I think it probably wouldn't power the equipment for very long. If I had this worked out, a contactor might be a more attractive option.

Having said that, critical fault for my system really means low temp or a cell went bad. The battery, inverter, etc is in it's own heated building. Heat is provided by a non-electric propane heater. I have a secondary electric heater setup on a lower temp. If the propane one dies, the electric will come on. I use the following values:


Voltages and SOC are approximate. On the upper side, there is really no way for a high system voltage fault unless there is equipment failure where the equipment is charging at higher than it's configured for. I don't use the inverter high cutout. On the low side, the generator will come on at 15% SOC. If the generator fails to start, then I have 15% of my battery left to figure out a fix.The gernerator voltage start points are in case the SOC drifts. I get alerts on generator activity. The inverter will cut out at about 5%, so I will have some battery left for troubleshooting. So in a nutshell, everything essentially operates within the BMS cutoff points.

One thing that Batrium is poor at is there are no alerts. IMO this would be an easy add on to the software, but for some reason it doesn't exist. You can set the software so it dumps status to a file every minute and I've been thinking or writing an alert engine that parses this file and sends alerts. Pretty crude way to go for something that should be an obvious need. There is guy who put together some tools to parse the UDP (iirc) broadcasts from the Batrium, but i haven't dug into it too deeply.

Subscribed and interested in this BMS. Hopefully one of my friends will decide to go with. I'm still observing and trying to see what my qualifications will be. Modular system and no mosfet are my favorite for serious full time set and forget ( assist only if tripped).
And is there other threads about this BMS that are explained in detail by real users and user experiences.