HELP! Which BMS?

[Nfluester]

First post so here goes ?

So i have just order 8 cells for Xuba and thier own case to put them in so thanks to reading recommendations here i am looking to build a 2P 4s 12v pack for our boat so i have the cells now sorted so next job to select the BMS.

i am not planning on trying to star the engines from the but would like to run a 1.2KW immersion heater through an inverter so >100ams load ideally and i dont really want to spend loads of money on it!

so basic balancing with low temp, low voltage and high voltage cut off

i have been considering:

123smart bms which looks to have a nice Ui through the phone and easy to setup and control nut those boards make it look like a mad science project and looks like lots of points of failure

Rec BMS looks like nice rugidised hardware but the setup and UI looks a bit old school with windows software and a laptop! and when you add all the bits up it looks pricey

the new big Daly something like a 200ah dual port they look nice but do i want to put my trust in something out of china with limited support

any thoughts on the above or other suggestions? chargery looked good but watched wills review and that put me off and the orion which i havent really looked at yet but think its expensive

thanks

 

[childcarepro]

Welcome, @Nfluester!

Oops, just noticed this should probably be in the BMS section rather than the battery bank section.

Have you decided yet? There are all kinds of BMS options out there, from cheap throwaways to thousands of dollars, and none of them is perfect, IMO. The ideal BMS IMO would be reasonably priced, reliable (read, high quality, overspec'ed components), do true active (cell to cell transfer) balancing, and be connected/smart w/ logging.

I was recently turned on to 123SmartBMS by @Dzl who has done fairly extensive research in this space. Looks really slick, but isn't perfect. I'm still working out whether this is the best option on balance. There is a bit of discussion in the SBMS thread which is one of the most active threads in the BMS area.

Pros of 123SmartBMS:
- simple, elegant installation right on battery terminals (no spaghetti wires!)
- quite reasonably priced for the elegance of the system
- per cell voltage and temperature tracking
- low temperature cutoff for charging and discharge
- 1A balancing current for top balancing (vs 200 mA for most)
- slick Bluetooth UI
- current tracking, not just voltage tracking
- per cell temp & voltage logging x 1 wk (not ideal for RVs not in full-time use)
- error logging (probably not limited to 1 wk?)
- use Victron Smart Battery Protects as relays for low voltage cutoff

Cons:
- dissipative balancing, not intercell transfer
- only top balancing, not constant balancing (confirmed with 123electric.eu)
- not full Victron integration, doesn't talk to MultiPlus or SmartSolar charge controller, but will stop charging above high voltage cutoff

I'm leaning toward the 123SmartBMS for all its pros. I might invest in a separate active balancer, but @WillProwse does say for most new batteries, active balancing is not that important.

As for high voltage and low voltage cutoffs, they're good safety measures to have in the BMS, but with a Victron system, not quite as important IMO because the Smart Battery Protects have low voltage cutoffs and their SCCs and inverter/chargers have high voltage cutoffs. But it's nice to have the extra layer of protection in the BMS in case the settings fail elsewhere in the system.

 

[Dzl]

I was recently turned on to 123SmartBMS by @Dzl who has done fairly extensive research in this space. Looks really slick, but isn't perfect. I'm still working out whether this is the best option on balance. There is a bit of discussion in the SBMS thread which is one of the most active threads in the BMS area.

Slight clarification, I actually don't personally know much about this specific BMS, I have done a fair bit of research and pondering on BMSes in general and a few in particular, but this is not one of the ones I'm very familiar with (though it has piqued my interest). I'm excited to hear what you learn about it!

Pros of 123SmartBMS:
- simple, elegant installation right on battery terminals (no spaghetti wires!)
- quite reasonably priced for the elegance of the system

I agree, its expensive compared to many of the popular commodity BMSes here, but its fairly reasonable for a full featured high quality BMS with proper documentation from a Western company.

- use Victron Smart Battery Protects as relays for low voltage cutoff

This is a nice feature (shared with the SBMS0 and some other BMSes). Be aware that Victron Battery Protect devices are not bi-directional (one way current only) and cannot be used directly in the inverter current path.

- not full Victron integration, doesn't talk to MultiPlus or SmartSolar charge controller, but will stop charging above high voltage cutoff

I hope further iterations or firmware updates might improve on this. The inverters might be harder to integrate with but I would think the smartsolar would be relatively simple.

I'm leaning toward the 123SmartBMS for all its pros. I might invest in a separate active balancer, but @WillProwse does say for most new batteries, active balancing is not that important.

It seems many people lately are finding (or maybe just assuming) active balancers are needed with the large capacity loosely matched 280Ah cells. But if it were me, I would start off with just the cells and the BMS and add an active balancer down the road if it is necessary (and it may well not be needed--particularly if you buy higher quality or lower capacity cells, or use your system conservatively).

As for high voltage and low voltage cutoffs, they're good safety measures to have in the BMS, but with a Victron system, not quite as important IMO because the Smart Battery Protects have low voltage cutoffs and their SCCs and inverter/chargers have high voltage cutoffs. But it's nice to have the extra layer of protection in the BMS in case the settings fail elsewhere in the system.

BMS high and low voltage disconnect is definitely an important feature, with or without Victron equipment. In my opinion, this is one of the most misunderstood features of a BMS. I would go so far as to say this is the most fundamental feature of a BMS (the ability to monitor and take actions based on cell level conditions).

What a BMS brings to the table is Cell Level monitoring and management (in this case cell level LVD and HVD). Many other components can monitor and take actions based on voltage or other conditions, but even with top quality components, this is pack level or bank level management/protection. This distinction is not meaningful with a theoretical perfectly matched pack, but the more mismatched the pack is, the more important cell level monitoring and management/protection is. No Victron component (apart from their BMS can see or take actions based upon cell level conditions), this is the specialization of the BMS.

 

[childcarepro]

Slight clarification, I actually don't personally know much about this specific BMS, I have done a fair bit of research and pondering on BMSes in general and a few in particular, but this is not one of the ones I'm very familiar with (though it has piqued my interest). I'm excited to hear what you learn about it!

Sorry I oversold your involvement! I didn't want to NOT give credit where credit was due.

I agree, its expensive compared to many of the popular commodity BMSes here, but its fairly reasonable for a full featured high quality BMS with proper documentation from a Western company.

Agreed. I want quality, and I'm willing to pay a modest amount more for it. 123SmartBMS seems a very fair balance of price/quality IMO, a sight better than REC, factoring in 123 Electric is in the Netherlands vs REC in Slovenia, with much higher overhead/labor costs.

Be aware that Victron Battery Protect devices are not bi-directional (one way current only) and cannot be used directly in the inverter current path.

Bummer; thanks for clarifying that for me. I was contemplating how to use the two (I have a 100A and a 220A Smart Battery Protect), whether one for 12V loads and one for 24V loads, or use one for DC loads and one for the inverter. I guess it'll have to be for 12V and 24V loads.

As for high/low voltage/temperature disconnect, 123Smart does have two small relays on the "out" board, but I'm not clear on their exact capabilities. The intro video on their website states (at 06:25) that when cell voltages/temps fall outside the range, "then one of the relays which I showed earlier [on the "out" board] will switch off, thereby disconnecting the charging or disconnecting the inverter." I emailed regarding the specifics of integration with Victron SmartBatteryProtect, SmartSolar SCCs, and MultiPlus inverter/chargers, and they responded:

"The BMS system can drive the Smart Battery Protects. They will work as relays. The BMS does not drive the [Victron] inverter or controller. It will only stop the process in case of a fail or emergency."

I'm happy it will stop the process, I'm just not clear on how. They do have a 500A contactor and a dual relay 12V x 120A x 2 or 24V x 100A x 2. I'm not sure whether I need to get those for the load/charge interrupt feature, or whether the built-in relays can do it on their own.

It seems many people lately are finding (or maybe just assuming) active balancers are needed with the large capacity loosely matched 280Ah cells. But if it were me, I would start off with just the cells and the BMS and add an active balancer down the road if it is necessary (and it may well not be needed--particularly if you buy higher quality or lower capacity cells, or use your system conservatively).

@WillProwse has mentioned multiple times with well matched new cells you don't need an active balancer. As for how well matched or how high quality... I have yet to hook up/test my cells. I inspected every cell, and they look brand new and feel like quality, but I paid only $1100 for 8 x 280Ah cells including shipping, so we'll see.

BMS high and low voltage disconnect is definitely an important feature, with or without Victron equipment. In my opinion, this is one of the most misunderstood features of a BMS. I would go so far as to say this is the most fundamental feature of a BMS (the ability to monitor and take actions based on cell level conditions).

What a BMS brings to the table is Cell Level monitoring and management (in this case cell level LVD and HVD). Many other components can monitor and take actions based on voltage or other conditions, but even with top quality components, this is pack level or bank level management/protection. This distinction is not meaningful with a theoretical perfectly matched pack, but the more mismatched the pack is, the more important cell level monitoring and management/protection is. No Victron component (apart from their BMS can see or take actions based upon cell level conditions), this is the specialization of the BMS.

Totally agree; the importance of BMSes for protecting high/low voltage cells from damage/fires/explosions cannot be overemphasized. I know that, but for some reason when I wrote that, I was totally ignoring individual cell voltages. Glad you stepped in to clarify that. I think I was a bit high on Victron's programmability and full-featured ecosystem when I downplayed the importance of those in MY situation, a situation that involves a fairly capable BMS.