Not to rehash the argument but I think the Chargery is completely set and forget. Use it as control and the SCC as the seatbelt. Again it's all whatever works best for you. But I do take exception that a Chargery needs babysitting.
ANT BMS. Final answer? Yes, final answer.
- Thread starter heirloom hamlet
- Start date
There are two points being mixed up here, actually three:
1) What is best equipped to enable and disable battery charging? My argument is the BMS because only it knows the battery state.
2) What is the protection? Depends on your needs and risk tolerance. Can be BMS, or charger protections, or even fully redundant master battery disconnect for life and death marine applications. Or just skip the seat belt altogether, if you're confident nothing will fail or can afford killing your lithium bank.
3) Do you even need a BMS at all? Your choice, if you don't have a BMS then you are the BMS. Personally I'd rather have something manage it for me.
1) What is best equipped to enable and disable battery charging? My argument is the BMS because only it knows the battery state.
2) What is the protection? Depends on your needs and risk tolerance. Can be BMS, or charger protections, or even fully redundant master battery disconnect for life and death marine applications. Or just skip the seat belt altogether, if you're confident nothing will fail or can afford killing your lithium bank.
3) Do you even need a BMS at all? Your choice, if you don't have a BMS then you are the BMS. Personally I'd rather have something manage it for me.
NEWYORKHILLBILLY
New Member
- Joined
- May 12, 2020
- Messages
- 136
I love this thread !!! I am new to it am an thinking no bms.
Here is my system on small travel trailer
380 PV on roof
victron MPTT smart controller
victron 712 battery monitor
280 am DIYy 4s lifepo4 battey
no inverter at this time but may add a under 500-800 watt
95% of time battery will charge off solar only , 5% converter running on generator or shore power .my current draws will 5-25 amps (except if i add the small inverter)
20% of the time a may be camping below freezing
I looking for simple set up like the battle born put it in and forget it.
so first thought a need a good BMS so i don't have to worry about things.
I been researching BMS on the forum and I watched all Wills videos
this has been my thought process
1.By a daly for its depenablty oh wait i might need a low temp disconnect
2. Oh great the new dalys have the low temp disconnect Oh no they lied as per wills video test. hmm
3. Oh new daly blue tooth has low temp disconnect . This is great found my solution .Hmm if they lied about last years model may this is not true . I Better send a email and confirm. well after 10 emails back and forth I still have no idea is some they say it does and in others they say it does not. (I cant wait for will review on this one) this my be teh BMS for me,but will not be able to confirm the low temp shut off until a forum member gets one and test it.
4. Better start looking for LTC BMS looking at the JBS-SP045020 (will recommends) seems to have good reviews . overkill solar sell a nice version of This with heavy duty wires. The blue tooth app has some pretty bad reviews. But this seems to be my best choice.Hmm maybe i should get something with a higher amp draw in case down the road I add a bigger inverter
5. Hmm Do i even need blue tooth? If the BMS does it job i really don't care what it doing. (this was battle born thought on there battery)
6. hmm what the BMS going to do. keep me from over and under charging , balance cells if need be and shut down if i draw to much % or low temp.
7. what if i use the mppt to control charging? also add a victron low voltage disconnect . hmm still need to solve the temp problem if i happen to be using converter power. I may be able to do that with a relay off the 712 battery monitor. Or if its below freezing i could just shut off converter manually . hmm what if maybe theirs a good way to shut off charging current out of converter something that may work with my victron stuff.I still working on this.
8. hmm so i still need to solve the balancing problem. oh found a 1.2 ballacer for under 10 bucks (will reviewed and tested this) hmm will this cheap thing do the job in long run . still thinking on that .
9. Where I am at today either no bms and solve these issues, or the JBS-SP045020
Because I new i may have overlooked something. I very capably of building the battery and setting all the settings , but when I done with it I like not have to worry about it and do a lot of monitoring of the battery . Maybe I overlooked something and there is a simpler way to do this. I sure wish the daly non blue tooth version had a low temp cut off. Who making the battle born BMS . that bms seems to fit my bill the best.
SO I still at the point to BMS or Not to BMS
I love this thread even know this BMS will not work in a 4S system
Here is my system on small travel trailer
380 PV on roof
victron MPTT smart controller
victron 712 battery monitor
280 am DIYy 4s lifepo4 battey
no inverter at this time but may add a under 500-800 watt
95% of time battery will charge off solar only , 5% converter running on generator or shore power .my current draws will 5-25 amps (except if i add the small inverter)
20% of the time a may be camping below freezing
I looking for simple set up like the battle born put it in and forget it.
so first thought a need a good BMS so i don't have to worry about things.
I been researching BMS on the forum and I watched all Wills videos
this has been my thought process
1.By a daly for its depenablty oh wait i might need a low temp disconnect
2. Oh great the new dalys have the low temp disconnect Oh no they lied as per wills video test. hmm
3. Oh new daly blue tooth has low temp disconnect . This is great found my solution .Hmm if they lied about last years model may this is not true . I Better send a email and confirm. well after 10 emails back and forth I still have no idea is some they say it does and in others they say it does not. (I cant wait for will review on this one) this my be teh BMS for me,but will not be able to confirm the low temp shut off until a forum member gets one and test it.
4. Better start looking for LTC BMS looking at the JBS-SP045020 (will recommends) seems to have good reviews . overkill solar sell a nice version of This with heavy duty wires. The blue tooth app has some pretty bad reviews. But this seems to be my best choice.Hmm maybe i should get something with a higher amp draw in case down the road I add a bigger inverter
5. Hmm Do i even need blue tooth? If the BMS does it job i really don't care what it doing. (this was battle born thought on there battery)
6. hmm what the BMS going to do. keep me from over and under charging , balance cells if need be and shut down if i draw to much % or low temp.
7. what if i use the mppt to control charging? also add a victron low voltage disconnect . hmm still need to solve the temp problem if i happen to be using converter power. I may be able to do that with a relay off the 712 battery monitor. Or if its below freezing i could just shut off converter manually . hmm what if maybe theirs a good way to shut off charging current out of converter something that may work with my victron stuff.I still working on this.
8. hmm so i still need to solve the balancing problem. oh found a 1.2 ballacer for under 10 bucks (will reviewed and tested this) hmm will this cheap thing do the job in long run . still thinking on that .
9. Where I am at today either no bms and solve these issues, or the JBS-SP045020
Because I new i may have overlooked something. I very capably of building the battery and setting all the settings , but when I done with it I like not have to worry about it and do a lot of monitoring of the battery . Maybe I overlooked something and there is a simpler way to do this. I sure wish the daly non blue tooth version had a low temp cut off. Who making the battle born BMS . that bms seems to fit my bill the best.
SO I still at the point to BMS or Not to BMS
I love this thread even know this BMS will not work in a 4S system
Battleborn does have a BMS built in and has lots of protections including low temp. It's a great option if you want simple and don't want to worry about things. It is a more bulky and more costly than if you DIY your own pack, but it is a good drop-in solution and you wouldn't need to do much.
NEWYORKHILLBILLY
New Member
- Joined
- May 12, 2020
- Messages
- 136
yes thats what i was saying I like to have there BMS in my DIY bateery . In my case there drop battery would not work as i didn't have room for the 2 i would need to get to 200ah, my DIY will only be slightly bigger and have 280ah
Speaking of @ghostwriter66, it's been over a week since she's been here. Hope everything is fine on the Texas Oil Fields...
ghostwriter66
"Here - Hold my Beer"
AAAGGGHH - well all these compnaies that usually sub-contract allot of work for us has now been just keeping their ppl home instead of paying them -- soooo us salaried ppl have actually had to get out of our PJ's and do work .... and it was 104 out here two days ago ... and then that night we got monsoon rain and hail ... and THEN I got our work truck stuck ... and it took them 3 hours to find me ... just been a long week .. LOL
heirloom hamlet
life my way
Dang, dude! I mean, dang guhrl!
@ghostwriter66 Figured it would be something like that - stay safe out there!
The only things you might be overlooking are (1) The fundamental advantage and purpose of a BMS is cell level protection, no other device is capable of that, if your cells are healthy and well balanced and matched, and you stay out of the knees, maybe this isn't necessary protection, but no other component has this capability, just be aware of that. (2) Low temp protection doesn't have to reside with the BMS, that is one logical place to incorporate it, but since you will be charging via solar 95% of the time, the SCC is another logical place for low temp protection, just make sure not to fire up the generator if your batteries are freezing (better yet, take reasonable steps to make sure your batteries don't freeze)
I think part of the differences of opinion come from use case (What Nordkyn designs for, and What Will designs for are very different beasts).
I think another part of the difference of opinion comes from wording. Up until this last comment, I disagreed with your perspective, but based on the way you've worded it in this last comment, I now see that not only do I mostly agree with you, but I've made similar arguments in the past.
I think a lot of us here are thinking about the same things in different ways. Setting aside integrated solutions like the SBMS0, I consider the BMS as having ultimate responsibility for battery protection, and the chargers as being primarily responsible for controlling charging. I look at this as "areas of responsibility" and "specialization." In the normal topology (discrete charge controller and BMS) there is overlap in these two roles, the BMS necessarily needs to be able to cutoff charging to fulfill its role as battery protector, but in normal operation it should be the charge controller that controls charging since it is better equipped to do so with more precise and sophisticated control in all areas except cell level monitoring and decision-making.
So I 100% agree with you that "The BMS is best equipped to enable and disable battery charging" but I disagree that "BMS is primary for charge control" In my eyes chargers are more capable of 'primary' charge control and the BMS should be the second line of control and step in only when a cell level parameter has been exceeded.
My perspective applies to the traditional topology, if you are imagining something different, or are making more of a theoretical argument for an alternative topology where the BMS and charge sources are more integrated and logic and control resides at the BMS, sortof a master/slave approach, then I can see where you are coming from, and maybe agree with you that this is a better approach (although you lose some redundancy/layered protection).
Can you be more specific what you are referring to and what specifically you are asking about?
Thanks very much for comments. And agreed on both! It takes a bit of dialog to ensure understanding. And Nordkyn's life and death marine use case is certainly different from most, which is especially relevant on his approach to having two separate layers--charge control and protection. But it's not clear to me that it matters when considering how to efficiently manage the battery's state. In normal operation, his use case is similar--trying to extract the most he can from limited charging sources on a boat, while keeping the battery healthy. And Electrodamus--different use case, efficient solar on the Canadian prairie, but same conclusion.
On that last sentence... could you expand a bit? Cell monitoring and decision-making seem like the most important functions, what else is there? The charging itself for LiFePO4 can be really simple, just do bulk until first cell hits target (which only the BMS knows) then terminate. You'll charge fast without long tails and still get to around 99% SOC. Unless maybe you're talking about MPPT for solar efficiency--different topic but doesn't preclude use of an MPPT charger in this model, with BMS deciding when to enable and disable the MPPT charger.
Yes my argument is architectural, not about the merits of existing components. It can be done today--with some BMS and some but not all chargers. You need the ability to remotely power on/off each charger and inverter, then BMS can control it via cheap control lines. The Victron line is one that could handle this already, more mixed with others, some could be hacked. But yes it could also be more integrated and simpler with just dumb charging sources that get turned on and off by BMS. No need for N different charging algorithms all competing with each other, nor the clunky interfaces on many chargers and inverters with limited levels of user settability.
And you can always add additional protection layers if you want. Multiple ways--battery or bus master disconnect relays controlled by BMS at wider thresholds than normal charging, add in a BatteryProtect on load bus for extra independent protection on the low end, could even use the charger built-in protections as a second layer but with wider thresholds for emergency protection--the reverse of the typical setup. I still think these are two separate questions:
1) What is best equipped to enable and disable battery charging? My argument is the BMS because only it knows the battery state.
2) What is the protection? Depends on your needs and risk tolerance.
Thanks for the detailed response. I think we are closer in thought than was first apparent.
It sounds a lot to me like a lot of what you are describing is basically the SBMS0's design model, is that more or less what you have in mind? If so we are definitely closer in thought, as that's the BMS I'm designing my system around, and my design model is not as extreme as Nordkyn, but probably closer to that than a hobby system, or backyard solar shed.
From an architectural/system design level, I definitely see the merits of an integrated approach with more centralized command and control, especially for a very purpose built system. At the same time I still see value in modular, flexible discrete, interoperable components, that are specialized and can function independently of any centralized control. But I think you probably wouldn't disagree with this approach either, because basically what I'm trying to describe is the SBMS0 + Victron topology.
So first off, I think this is likely one more place where we are thinking roughly the same thing in different ways. I like the concept of the BMS enabling/disabling charge sources as necessary.
Yes, basically, though I mean it in a broader conceptual sense. I don't think its a different topic at all. I see this as coming back to what I said earlier about role and specialization. The BMS has specific insight into individual cell level voltages and is primarily responsible for the safety and health of the battery, an MPPT charge controller has specific insight into PV conditions and is primarily responsible for efficiently and safely supplying power to the system.
I haven't fully thought this through, but in the case of another charge source like the vehicle charging system, the same distinction would apply, a device like the Orion-TR smart, would have some specific insight into the state of the vehicle electrical system.
None of this precludes your argument about the BMS being best equipped to enable/disable charging. And I don't disagree. But--at least how I'm thinking about it right now, and my thoughts may evolve--to me it seems logical for the BMS to control when to charge, and the chargers to control how to charge. (I like this conversation, just in writing these last 3 paragraphs I've wrestled with, thought and rethought a few ideas--definitely a good thought experiment).
There is also the situation where you want to stop charging to the battery but allow your chargers to power your loads, would this be possible in your design? If the chargers simply charge and are switched on/off by the BMS based on cell level voltage conditions, I don't see how this would be possible unless another level of logic and control was built into the BMS.
Could you expand on what you mean by compete? I'm not sure I understand this.
This is a side issue/non-issue in my opinion. their are lots clunky interfaces/UIs, but Victron (and their modular 'ecosystem' approach) has some of the cleanest most intuitive interfaces I've seen, especially when compared with a lot of the BMS UIs
To me, I still see the chargers and load control devices (inverter, smart battery protect, etc) as the first line of control and protection, and the BMS as the backstop and/or ultimate line of protection. I like the concept of the BMS being able to switch charging on/off directly but I still see this as the second line of defense & control as its more of a blunt instrument. But I think my perspective is more based on what currently exists, than what could exist, when compared to yours. In an ideal situation, I could see many advantages to much more integration and blurring the lines between a BMS and charge controller.
You've definitely got me thinking about a lot though, I wouldn't be at all surprised if my thoughts on the matter continue evolving.
It sounds a lot to me like a lot of what you are describing is basically the SBMS0's design model, is that more or less what you have in mind? If so we are definitely closer in thought, as that's the BMS I'm designing my system around, and my design model is not as extreme as Nordkyn, but probably closer to that than a hobby system, or backyard solar shed.
From an architectural/system design level, I definitely see the merits of an integrated approach with more centralized command and control, especially for a very purpose built system. At the same time I still see value in modular, flexible discrete, interoperable components, that are specialized and can function independently of any centralized control. But I think you probably wouldn't disagree with this approach either, because basically what I'm trying to describe is the SBMS0 + Victron topology.
So first off, I think this is likely one more place where we are thinking roughly the same thing in different ways. I like the concept of the BMS enabling/disabling charge sources as necessary.
Yes, basically, though I mean it in a broader conceptual sense. I don't think its a different topic at all. I see this as coming back to what I said earlier about role and specialization. The BMS has specific insight into individual cell level voltages and is primarily responsible for the safety and health of the battery, an MPPT charge controller has specific insight into PV conditions and is primarily responsible for efficiently and safely supplying power to the system.
I haven't fully thought this through, but in the case of another charge source like the vehicle charging system, the same distinction would apply, a device like the Orion-TR smart, would have some specific insight into the state of the vehicle electrical system.
None of this precludes your argument about the BMS being best equipped to enable/disable charging. And I don't disagree. But--at least how I'm thinking about it right now, and my thoughts may evolve--to me it seems logical for the BMS to control when to charge, and the chargers to control how to charge. (I like this conversation, just in writing these last 3 paragraphs I've wrestled with, thought and rethought a few ideas--definitely a good thought experiment).
There is also the situation where you want to stop charging to the battery but allow your chargers to power your loads, would this be possible in your design? If the chargers simply charge and are switched on/off by the BMS based on cell level voltage conditions, I don't see how this would be possible unless another level of logic and control was built into the BMS.
Could you expand on what you mean by compete? I'm not sure I understand this.
This is a side issue/non-issue in my opinion. their are lots clunky interfaces/UIs, but Victron (and their modular 'ecosystem' approach) has some of the cleanest most intuitive interfaces I've seen, especially when compared with a lot of the BMS UIs
To me, I still see the chargers and load control devices (inverter, smart battery protect, etc) as the first line of control and protection, and the BMS as the backstop and/or ultimate line of protection. I like the concept of the BMS being able to switch charging on/off directly but I still see this as the second line of defense & control as its more of a blunt instrument. But I think my perspective is more based on what currently exists, than what could exist, when compared to yours. In an ideal situation, I could see many advantages to much more integration and blurring the lines between a BMS and charge controller.
You've definitely got me thinking about a lot though, I wouldn't be at all surprised if my thoughts on the matter continue evolving.
Pierre
Somewhere down South
- Joined
- Dec 21, 2019
- Messages
- 1,129
I tend to agree. What happens in the case of a 'drop in replacement' LFP battery , as a lot of them are marketed. The on board BMS is the only device to regulate the OV scenario - no other layers of protection and 100 to 1 the existing charger does not have a LFP charge profile to control CC/CV.
If the installation requires a special charger to be installed as well then it is not a 'drop in replacement'
Yes that's right. That is what got me thinking about this, as well as the approach of other users such as Cal.
I agree with that, partially. I think the chargers know more about how to extract the power. Like your examples--solar chargers try to maximize power extracted, whether MPPT or PWM or the Electrodacus approach of matched panels vs. voltage with SSR control. DC-DC can buffer the vehicle system from the house bank. But they all translate that to the same desired bulk charge voltage, and after that I think the BMS should assume control and gate when they can charge.
Good point, although my first thought is that I'd like to have the loads discharge the battery for a while down to a desired lower SOC, and then trigger a new round of bulk charge. Rather than leave the bank indefinitely at high SOC with chargers supplying loads.
Well they don't compete in delivering charge, the LiFePO4 battery will take whatever it can take. But some chargers do some periodic sampling of OC voltage (brief, so not super accurate) by interrupting charge briefly, sampling the voltage, and then factoring that into their algorithm. But if another charger is also running, that reading will be bogus. But neither charger knows about the other, nor about any load current. So what if that first charger keeps absorption going longer because its algorithm is screwed up? How can you know? I just dislike the idea of multiple unknown and disconnected algorithms managing the charge state of the battery, again with the BMS in control there is none of that.
Likewise, I'm still learning about all this and appreciate the good discussion.
Yes drop-ins are a whole different question, most or all "drop in" batteries inherently can't do what I'm talking about. Its internal BMS implements the protections and that's it. If they had external communication and control they could. Victron smart batteries have some of that but they are extremely expensive.I tend to agree. What happens in the case of a 'drop in replacement' LFP battery , as a lot of them are marketed. The on board BMS is the only device to regulate the OV scenario - no other layers of protection and 100 to 1 the existing charger does not have a LFP charge profile to control CC/CV.
If the installation requires a special charger to be installed as well then it is not a 'drop in replacement'
I'm looking for some clarity on the "Coulomb counting" the Ant BMS advertises. Does it accurately measure state of charge? how?
I'm familiar with shunt based and hall sensor based monitoring but this doesn't appear to (to my untrained eye) use either method. Are there other accurate methods (the ad states ~5% accuracy).
I'm familiar with shunt based and hall sensor based monitoring but this doesn't appear to (to my untrained eye) use either method. Are there other accurate methods (the ad states ~5% accuracy).
apctjb
Solar Enthusiast
- Joined
- Jun 16, 2020
- Messages
- 472
Dumb question perhaps; reading the above it appears you can connect charging source (if you choose) directly to battery and the Ant BMS will still function (I wonder if the Coulomb counter will still work?). So can you also connect discharge sources direct to the battery and use the ANT BMS to provide cell level monitoring and balancing but not battery disconnect function. Or are there less expensive BMS like devices that provide cell monitoring and balancing but don't offer disconnect (FET or otherwise)?
