[tmalcolm]

I think many (most?) BMS's have a low voltage disconnect. Based on the specs for my SOK's it does seem that it is intended as a failsafe and not as a normal operation control "Recommend low voltage disconnect: 11.2V - BMS discharge cut-off voltage: Around 10.4V - Reconnect Voltage:>11.6V " Probably not good for the battery to go below 11.2V often. So I guess some sort of cut off for the 12V loads might be a good idea if that was becomes a frequent event. Of course one would need some sort of data logging to know how oten the batteries were in that 10.4>111.2 range.

Looking at the specs, it does not look like the BP , it is sort of disappointing that there is just a choice of fixed settings where disconnect and reconnect are paired. None of which seem to play very well with the spes for SOK's.

If I was t chose 11.25V cut off, then it won't reconnect until 13.8V whereas the BMS is good to go at 11.6V
There is a 11.5V setting that reconnects at 12.8V so give up a little capacity to reduce reconnect voltage.
Where charging is by alternator (or shore power) it would seem these settings are leaving the system off muche longer that necessary. Never thought about any of this stuff before. Always good to RTFM.


View attachment 183694

Yea, too bad I can't select actual values. Though I suppose these are close enough. Per this chart, I think I would go with 12.0v low cutoff for the BP, restart at 13.0V. Agreed, it seems a long time between cutoff and restart.
I'll use the Cerbo to also track and activate a buzzer before the cutoff to eliminate that period altogether.

 

[njvagabond]

Yea, too bad I can't select actual values. Though I suppose these are close enough. Per this chart, I think I would go with 12.0v low cutoff for the BP, restart at 13.0V. Agreed, it seems a long time between cutoff and restart.
I'll use the Cerbo to also track and activate a buzzer before the cutoff to eliminate that period altogether.

What kind of batteries will you be using?

 

[tmalcolm]

What kind of batteries will you be using?

I have three battleborn 100a batts

 

[jkmann]

I'm confused by the statement that the SBP can't "cut the circuit." That device is a one-way switch that will open when the battery voltage drops below the programmed voltage. It also has an "allowed to discharge" low-current control connection that can be used to open the high-current switch. I have the SBP 220A in my system controlled by the VE Bus BMS.

Possibly I do not understand the discussion here.

 

[tmalcolm]

I'm confused by the statement that the SBP can't "cut the circuit." That device is a one-way switch that will open when the battery voltage drops below the programmed voltage. It also has an "allowed to discharge" low-current control connection that can be used to open the high-current switch. I have the SBP 220A in my system controlled by the VE Bus BMS.

Possibly I do not understand the discussion here.

Hi JK, bit of confusion. We're referring to the smart shunt that cannot cut the circuit. You're correct in that the SBP can indeed cut the circuit. Apologies if there was a typo-brainfart somewhere above

 

[gregoryx]

I think many (most?) BMS's have a low voltage disconnect. Based on the specs for my SOK's it does seem that it is intended as a failsafe and not as a normal operation control "Recommend low voltage disconnect: 11.2V - BMS discharge cut-off voltage: Around 10.4V - Reconnect Voltage:>11.6V " Probably not good for the battery to go below 11.2V often. So I guess some sort of cut off for the 12V loads might be a good idea if that was becomes a frequent event. Of course one would need some sort of data logging to know how oten the batteries were in that 10.4>111.2 range.

Looking at the specs, it does not look like the BP , it is sort of disappointing that there is just a choice of fixed settings where disconnect and reconnect are paired. None of which seem to play very well with the spes for SOK's.

If I was t chose 11.25V cut off, then it won't reconnect until 13.8V whereas the BMS is good to go at 11.6V
There is a 11.5V setting that reconnects at 12.8V so give up a little capacity to reduce reconnect voltage.
Where charging is by alternator (or shore power) it would seem these settings are leaving the system off muche longer that necessary. Never thought about any of this stuff before. Always good to RTFM.
...

Agreed. And one of the reasons I wouldn't bother with the SBP. Pretty sure the Battle-Borns have that cut-off as well.

I consider the BP in that category of products that should have a different brand on it or something. Maybe somewhere down the road, Victron will improve the management and integration of more of their products and the Orions and SBP and such will become more useful. I assume that if one uses the Victron batteries with their BMS, this is all covered. I like the idea that an increasing number of batteries eliminate the need for an SBP or Shunt as their internal BMS communicates directly with the Cerbo - taking the place of the SS, for example, and giving SOC as well as voltage and temps. I'll find out how accurate this is if/when I implement the EG4 batteries into a Cerbo.


... or... maybe I'm wrong...

I'm confused by the statement that the SBP can't "cut the circuit." That device is a one-way switch that will open when the battery voltage drops below the programmed voltage. It also has an "allowed to discharge" low-current control connection that can be used to open the high-current switch. I have the SBP 220A in my system controlled by the VE Bus BMS.
...

@jkmann, you're saying the SBP is "controlled by the VE.Bus BMS." I don't see a VE.bus or VE.direct or other connection to the SBP. I read the manual as saying that it can send a Bluetooth signal or something like that... but wasn't sure that made sense. It shows up on a VenusOS system as a device? Or do you mean by using the signal/remote line off of it?

Yea, too bad I can't select actual values. Though I suppose these are close enough. Per this chart, I think I would go with 12.0v low cutoff for the BP, restart at 13.0V. Agreed, it seems a long time between cutoff and restart.
I'll use the Cerbo to also track and activate a buzzer before the cutoff to eliminate that period altogether.

The BP settings chart supports my suspicion that this device is pre-lithium vintage. According to my trusty chart below, 12V is below 10% SOC on a typical lithium battery. And 13V is ~40%. The rest of the voltage options for the BP are certainly not functional for lithiums. The chart below numbers are open-circuit estimates, of course, so if you add any load the voltages will be lower and things get weirder.

I would go another route until Victron updates the BP units. Unless the SBP can be controlled via Cerbo - more like a relay - and then it would make sense. IOW, dumber unit but controlled by the smarts of the Venus OS system.

 

[jkmann]

@jkmann, you're saying the SBP is "controlled by the VE.Bus BMS."

Yes, the VE Bus BMS has an "allowed to discharge" port. This connects via a small wire (1A max) to the "H" port on the SBP. When the VE Bus BMS sends a battery (+) voltage the SBP switch is closed and current is allowed to flow through the SBP. When the VE Bus BMS drops the voltage and allows that wire to free-float then the SBP switch immediately opens and current stops across the SBP. It's actually a very functional way to protect your Victron batteries because it operates based on battery voltage at a cell level as well as protecting against out-of-temperature conditions. Of course you can connect any BMS to the "H" terminal. It doesn't know what is controlling it.

If you don't want to directly control the SBP with a BMS or other device, it can respond to the voltage difference between the large (+) supply cable and a small (-) ground cable. This is a programmable setting, but it only works at the gross voltage level, not at the individual cell level within your batteries.

 

[tmalcolm]

Great input! Contacting Battleborn for their SOC charts and further info on their BMS and if they have any advice on low v protection without using the SBP. Update tomorrow...

 

[gregoryx]

Yes, the VE Bus BMS has an "allowed to discharge" port. This connects via a small wire (1A max) to the "H" port on the SBP. When the VE Bus BMS sends a battery (+) voltage the SBP switch is closed and current is allowed to flow through the SBP. When the VE Bus BMS drops the voltage and allows that wire to free-float then the SBP switch immediately opens and current stops across the SBP. It's actually a very functional way to protect your Victron batteries because it operates based on battery voltage at a cell level as well as protecting against out-of-temperature conditions. Of course you can connect any BMS to the "H" terminal. It doesn't know what is controlling it.

If you don't want to directly control the SBP with a BMS or other device, it can respond to the voltage difference between the large (+) supply cable and a small (-) ground cable. This is a programmable setting, but it only works at the gross voltage level, not at the individual cell level within your batteries.

Interesting. So... no, they don't speak VE.anything. But the SBP is basically a component of the external BMS for the Victron batteries. IOW, with the Victron batteries, you need a Victron BMS and a Victron SBP to get the results of the internal BMS on most LFP batteries. Ugh. I mean... sort of cool... but also, ugh.

Advances my belief that the best batteries for the Victron system are ones that show up in the Cerbo as a battery unit and report the voltage and SOC from the internal BMS. I haven't witnessed it personally, but I understand there are a stack of them that do it now. I'm hoping to test that out on the EG4-LL batteries soon-ish.



@tmalcolm, BB says their low voltage cutoff in their BMS is 10V with a reconnect of 10V. They recommend setting 10.5V on your own disconnect / discharge limits. (Taken from their docs.)

 

[jkmann]

Interesting. So... no, they don't speak VE.anything. But the SBP is basically a component of the external BMS for the Victron batteries. IOW, with the Victron batteries, you need a Victron BMS and a Victron SBP to get the results of the internal BMS on most LFP batteries. Ugh. I mean... sort of cool... but also, ugh.

Advances my belief that the best batteries for the Victron system are ones that show up in the Cerbo as a battery unit and report the voltage and SOC from the internal BMS. I haven't witnessed it personally, but I understand there are a stack of them that do it now. I'm hoping to test that out on the EG4-LL batteries soon-ish.



@tmalcolm, BB says their low voltage cutoff in their BMS is 10V with a reconnect of 10V. They recommend setting 10.5V on your own disconnect / discharge limits. (Taken from their docs.)

Victron also makes "drop in" batteries with an integrated BMS ... but the SmartLithium batteries with the VE Bus external BMS with the companion control system connections for the Multiplus, SBP, Solar Charge Controller, and B2B Charger (Orion), is a very efficient and easy to implement approach. You don't need the Cerbo at all if you use the VE Bus BMS, and you can read pretty much all the device data directly on Victron Connect. With the latest version of Victron Connect and device firmware, the key current data is all displayed for each device on Victron Connect without opening each one separately, so you can monitor the health of your system at a glance. Having implemented this system, it's hard to see how a system could be simpler without losing functionality.

 

[tmalcolm]

I spoke to Battleborn. They reconfirmed Design 1 (see original post) is workable. Design 2 is not, due to the issue identified in this thread of the Inverter frying the SBP device (smart battery protect) because of inverter cap charging. This is not an issue because the Phoenix 1200 has a low voltage cutoff and I can connect it to the input side where the batteries are (as opposed to the load side) of the SBP.
So low battery protect with regards to DC loads can be managed by the SBP and the AC loads can be managed by the inverter.
Also, it was pointed out to me by the Battleborn rep (AGAIN, RTFM) the SBP has user defined voltage level choices, not just the convenient (but not applicable to lithium batteries as Gregoryx pointed out) presets.
This BB chart shows very similar values to Gregory's chart. Just have to be sure that I set the SBP cutoff high enough to make sure I don't go into a battery shutdown mode when some load surge happens when the batteries are at a low SOC. This would require jumping the battery to get it going again as the internal BMS shuts it down at 0% charge, according to Battleborn.

Also, these are internally heated batteries so if the the heater is enabled, it will use energy as needed to keep the cells at a minimum functional temp right into shutdown. So need to keep that in mind too in the winter.
Huge thanks to everyone for all the insights. Super useful, as always. All things considered, my current list of components will work, although maybe not as comprehensively in terms of monitoring and control as other arrangements that have been discussed might provide. So looks like I'll stay with my current components, keeping in the mind the possible caveats.
Comments?? Did I still over look something?

BTW Gregory, where did you get your SOC chart?

 

[njvagabond]

SBP has user defined voltage level choices

Thanks for pointing that out!!

Upon further review of the instant replay, it looks like Victron does sneak that into the manual in this one statement
"7. Set the preset to the desired combination of shutdown and restart voltage or tap on User defined to define a custom combination." I suppose they don't show it in the table since it is not accessible via the grounding procedure on the device? Not sure why there is no documentation of the bluetooth app in the manual. Here is one of Ross Lukeman's excellent videos (time stamped) to that show that configuration option on the app.

 

[tmalcolm]

Thanks for pointing that out!!

Upon further review of the instant replay, it looks like Victron does sneak that into the manual in this one statement
"7. Set the preset to the desired combination of shutdown and restart voltage or tap on User defined to define a custom combination." I suppose they don't show it in the table since it is not accessible via the grounding procedure on the device? Not sure why there is no documentation of the bluetooth app in the manual. Here is one of Ross Lukeman's excellent videos (time stamped) to that show that configuration option on the app.

Yes, agreed. Victron almost seems to be actively hiding that feature. Yea, I like Ross Lukeman. Quality stuff! Thanks for sharing this one

 

[Scalf77]

Also if you look at the supported inverter config in the SBP manual, you can see that the inverter can be controlled remotely via the SBP by attaching the Remote input to the 12 volt load output of the SBP. The SBP disconnects from battery the remote control will turn off inverter.

The user programable function is with the Bluetooth enabled units, it is also in the manual. You do need to make sure that you have the manual for the latest units. I have found that many of the detailed features of Victron equipment needs to be consumed via reading the manual, their datasheets are usually to high level to really incorporate the important details.

Another important detail to take into consideration, other than battery temperature heater usage is the consumption of the SBP unit itself. Even when the loads are off the SBP itself will consume 0.7mA to 0.9mA depending on Bluetooth. Also usually the Smartshunt is less than 1mA. The Cerbo GX also is a consumer, but that could be off of the load side. While not large current consumption, you should take into account that these will be active even after the load disconnect has occurred. I generally find a manual high current disconnect switch to be a requirement. ( That is not shown in your high level diagram )

As @gregoryx said you could have seeing as your are already installing the Smart Shunt and Cerbo GX just used a relay on the Cerbo to control a large latching battery switch. Units like the BlueSea 7713 would disconnect when 12 volt control voltage is disconnected via the Cerbo relay. This could be done with SOC level or voltage level.

@jkmann, I agree the latest Victron Connect APP updates make monitoring your system very easy, but you are still limited to Bluetooth range. As you have pointed out you can put together a very robust designed Victron System without the a Cerbo GX. As with all things it comes down to cost and preferences.

@gregoryx I have been one of those that has recently been enabled to bring my non-victron battery or BMS as a supported device in my Cerbo GX. Overall I am happy with the ability to do so, all my Victron Charge devices are now charging based on data they receive from my BMS (RV-C) output. Now instead of seeing Bulk, and Absorption I see External Control when charging. The other great part of that is that I can now see most of the data my BMS app had on it as a Cerbo GX battery monitor device. Nicely the battery temp (the same temp value the BMS see's ) can be displayed in via the cerbo and and VRM.

 

[njvagabond]

Also if you look at the supported inverter config in the SBP manual, you can see that the inverter can be controlled remotely via the SBP by attaching the Remote input to the 12 volt load output of the SBP. The SBP disconnects from battery the remote control will turn off inverter.

Thanks for this info. Maybe you can help me with this question.
Is the benefit of using the SBC with the inverter remote vs relying on the low voltage disconnect setting that the SBC would have less parasitic draw then the inverter when it is in low voltage disconnect? Did not see anything in the Multiplus manual (in my case). Admittedly, I don't seem to pick up well on the many of details/fine points in the documentation.

 

[Scalf77]

Thanks for this info. Maybe you can help me with this question.
Is the benefit of using the SBC with the inverter remote vs relying on the low voltage disconnect setting that the SBC would have less parasitic draw then the inverter when it is in low voltage disconnect? Did not see anything in the Multiplus manual (in my case). Admittedly, I don't seem to pick up well on the many of details/fine points in the documentation.

I would suspect that yes if using the internal low voltage disconnect, that you would have some current consumption as it monitors voltage to know when to turn back on. I don't suspect it would be much, but should be acknowledged. I would think the hard wired remote would be so you could keep the devices in sync with the managed load shut down. I believe a bigger drawback would be as wired the inverter would always be on with remote solution, although external switch could be placed in line and remedy that.

The Multiplus has a remote connection (H terminal), but not the same as the Phoenix as it needs to handle charger and inverter. It would be a bit more complicated but doable if someone wanted to come up with that scheme, I would probably just stick the internal settings of the inverter

 

[tmalcolm]

Also if you look at the supported inverter config in the SBP manual, you can see that the inverter can be controlled remotely via the SBP by attaching the Remote input to the 12 volt load output of the SBP. The SBP disconnects from battery the remote control will turn off inverter.

The user programable function is with the Bluetooth enabled units, it is also in the manual. You do need to make sure that you have the manual for the latest units. I have found that many of the detailed features of Victron equipment needs to be consumed via reading the manual, their datasheets are usually to high level to really incorporate the important details.

Another important detail to take into consideration, other than battery temperature heater usage is the consumption of the SBP unit itself. Even when the loads are off the SBP itself will consume 0.7mA to 0.9mA depending on Bluetooth. Also usually the Smartshunt is less than 1mA. The Cerbo GX also is a consumer, but that could be off of the load side. While not large current consumption, you should take into account that these will be active even after the load disconnect has occurred. I generally find a manual high current disconnect switch to be a requirement. ( That is not shown in your high level diagram )

As @gregoryx said you could have seeing as your are already installing the Smart Shunt and Cerbo GX just used a relay on the Cerbo to control a large latching battery switch. Units like the BlueSea 7713 would disconnect when 12 volt control voltage is disconnected via the Cerbo relay. This could be done with SOC level or voltage level.

@jkmann, I agree the latest Victron Connect APP updates make monitoring your system very easy, but you are still limited to Bluetooth range. As you have pointed out you can put together a very robust designed Victron System without the a Cerbo GX. As with all things it comes down to cost and preferences.

@gregoryx I have been one of those that has recently been enabled to bring my non-victron battery or BMS as a supported device in my Cerbo GX. Overall I am happy with the ability to do so, all my Victron Charge devices are now charging based on data they receive from my BMS (RV-C) output. Now instead of seeing Bulk, and Absorption I see External Control when charging. The other great part of that is that I can now see most of the data my BMS app had on it as a Cerbo GX battery monitor device. Nicely the battery temp (the same temp value the BMS see's ) can be displayed in via the cerbo and and VRM.

Thanks for that Scalf77. Agreed, the SBP remote can be used to shutoff the inverter as soon as the SBP turns off. I'll take the power consumption of these devices in consideration. Small yes, but over time, in the right circumstance could make a difference indeed.
I also plan to use the CerboGX to monitor and/or control other variables like water (fresh and gray) levels, propane level, temperature/humidity (with the newer ruuvi device)

 

[tmalcolm]

@gregoryx I have been one of those that has recently been enabled to bring my non-victron battery or BMS as a supported device in my Cerbo GX. Overall I am happy with the ability to do so, all my Victron Charge devices are now charging based on data they receive from my BMS (RV-C) output. Now instead of seeing Bulk, and Absorption I see External Control when charging. The other great part of that is that I can now see most of the data my BMS app had on it as a Cerbo GX battery monitor device. Nicely the battery temp (the same temp value the BMS see's ) can be displayed in via the cerbo and and VRM.

How is this accomplished? Can you elaborate?

 

[gregoryx]

...
@jkmann, I agree the latest Victron Connect APP updates make monitoring your system very easy, but you are still limited to Bluetooth range. As you have pointed out you can put together a very robust designed Victron System without the a Cerbo GX. As with all things it comes down to cost and preferences.

@gregoryx I have been one of those that has recently been enabled to bring my non-victron battery or BMS as a supported device in my Cerbo GX. Overall I am happy with the ability to do so, all my Victron Charge devices are now charging based on data they receive from my BMS (RV-C) output. Now instead of seeing Bulk, and Absorption I see External Control when charging. The other great part of that is that I can now see most of the data my BMS app had on it as a Cerbo GX battery monitor device. Nicely the battery temp (the same temp value the BMS see's ) can be displayed in via the cerbo and and VRM.

Agreed on that first bit: the Bluetooth is super cool when in the rig; but the always-available (when given a full-time internet connection) is really more useful and valuable - not to mention the potential logic-based stuff. That said... they've done some pretty cool Bluetooth stuff and they've got the competition doing it now as well; but their online ease-of-implementation is pretty hard to beat at the price-point and simplicity - which still offering much more advanced features if one wants to go there.


I'm really glad to hear how well the BMS communication part is working! I was assured by two battery vendors that it was so... but I'm always a bit skeptical until I see it implemented. What batteries are you running? Or is it a DIY pack? if so, what BMS?

I'm planning to implement a stack of EG4-LL batteries at home for storage and I'm eager to see this new magic work! 🧐

 

[Scalf77]

I'm really glad to hear how well the BMS communication part is working! I was assured by two battery vendors that it was so... but I'm always a bit skeptical until I see it implemented. What batteries are you running? Or is it a DIY pack? if so, what BMS?

I'm planning to implement a stack of EG4-LL batteries at home for storage and I'm eager to see this new magic work! 🧐

I have a Lithionics Battery with their external BMS. I had to make up a cable and update my BMS firmware, but it was pretty painless. From a operational standpoint, I haven't noticed much difference (my absorption phase may be longer). The BMS is communicating with the Cerbo and shares the charging voltage and max charge current. Like I said the bigger thing is that the Lithionics BMS is now a Cerbo Device.