BMS with limited load current

[Ampster]

I was wondering if BMS's in general limit their continuous output load current or if they just cut off the load on a current threshold? If the latter, are there BMS's available where you can adjust the maximum continuous ouput load current?

Can we start over to keep it simple and clarify which question is being answered? To answer the first question it is the latter. A BMS can only "cut off the load on a current threshold". There are no BMSs that can adjust the continuous output load current. There are some in which the setting for maximum output can be adjusted but those still just cut off the load when current reaches that setting.

Is there a way I or others can help you understand alternatives ways to regulate current drawn from your batteries? Some alternatives have already been suggested. I agree with your statement about assumptions. In this case I am of the opinion that an incorrect assumption has been made about how current to and from batteries can be controlled.

 

[RHTizzy]

Thanks for your clarity and perspective. That was my understanding to begin with too, but it contradicts with the sales rep and also the user manual depictions, so I came here....

And then also Ancient confirmed the Seplos sales rep statements, sadly without proof so I'm still sceptical. Then things got convoluted with assumptions based on something, perhaps hubris or maybe just willingness to be important or maybe just the trap of self belief, whatever. I dont care, I am glad you're trying to help and I appreciate and respect your opinions. As you can see, I have not refuted any opinions I dont agree with. You are entitled to them and the truth will come out, if not here then elsewhere and that's all that matters in the end.

Anyways, so now would be the time for Ancient to jump in and retract or strengthen his statement that his Seplos can do it then and we will either forgive the incomptence because after all, he is only trying to help and we all are guilty of misunderstanding and miscommunication at some time, or the world will know that there are indeed BMS's that can regulate load current and Seplos are not full of sheit...

But perhaps Ancient is no longer willing to partake in something that might stain his standing here, which I also understand and forgive, because ignorance stings and bites us all at some time...

EDIT, your second reply got me while I was typing. memo to self: keep answers brief and concise

 

[houseofancients]

Thanks for your clarity and perspective. That was my understanding to begin with too, but it contradicts with the sales rep and also the user manual depictions, so I came here....

And then also Ancient confirmed the Seplos sales rep statements, sadly without proof so I'm still sceptical. Then things got convoluted with assumptions based on something, perhaps hubris or maybe just willingness to be important or maybe just the trap of self belief, whatever. I dont care, I am glad you're trying to help and I appreciate and respect your opinions. As you can see, I have not refuted any opinions I dont agree with. You are entitled to them and the truth will come out, if not here then elsewhere and that's all that matters in the end.

Anyways, so now would be the time for Ancient to jump in and retract or strengthen his statement that his Seplos can do it then and we will either forgive the incomptence because after all, he is only trying to help and we all are guilty of misunderstanding and miscommunication at some time, or the world will know that there are indeed BMS's that can regulate load current and Seplos are not full of sheit...

But perhaps Ancient is no longer willing to partake in something that might stain his standing here, which I also understand and forgive, because ignorance stings and bites us all at some time...

EDIT, your second reply got me while I was typing. memo to self: keep answers brief and concise

Perhaps you shouldnt do all these assumptions, and simply RTFM

The seplos BMS will hard throttle to 10a when triggered
Next to that you can set a max charge and discharge rate, which, if used in combination with a proper inverter and comms will throttle your charge and discharge rate to exactly what you set

 

[RHTizzy]

I'm happy for your reply and can appreciate some of your faith in manuals. You have my thanks and goodwill.

 

[RHTizzy]

Perhaps you shouldnt do all these assumptions, and simply RTFM

The seplos BMS will hard throttle to 10a when triggered
Next to that you can set a max charge and discharge rate, which, if used in combination with a proper inverter and comms will throttle your charge and discharge rate to exactly what you set

I just finished reading a few manuals (thanks for the uploads everyone) and not a single one mentions a semblance of maximum DIScharge rate, only threshold and transient. Both of which implement full lockdown on discharge. Interestingly enough the 10A hard throttle you use as validation for your argument is only valid for charging.

Pity, you almost had me convinced you were reliable and knew what you were talking about.

I'll wait for the Seplos engineers to get back to work after the chinese new years holiday and post back their perspective.

 

[houseofancients]

From the manual



Next to that one can set a max charge and Max discharge that will be communicated to any sorts of modern inverter using BMS inverter communication..

On a side note, you're not only a lost case, but a nasty one at that.
I suggest you get your shit together and learn to behave like an adult.

Untill such time you are not worth my time and will be blocked

 

[Ampster]

@RHTizzy
What @houseofancients and the manual are referring to is when the BMS is in closed communication with the inverter. If that confuses you I would be happy to explain in detail.
Since you persistently want to ignore or misinterpret what we have said I will let you wait until the Chinese Engineers return from Spring Festival. I am sure you will enjoy throwing insults at them as well. Good luck with that approach to dialogue.
For the benefit of other readers, closed communications, still does not change the concept that BMSs do not have the ability to directly regulate current. What that means is that the BMS is communicating to the inverter to change the current which the inverter draws. That is consistent with what I and @LakeHouse and @houseofancients have been saying from the first posts. It is also consistent with physics in which current flow is most often determined by the load which pulls the current from the source. Without a load, current will not flow. There are exceptions if anyone wants the details but it is never been my experience in fifteen years dealing with many different BMSs that I have seen a BMS that can directly control loads other than by disconnecting the source.

 

[hwy17]

You can't throttle current. No BMS can do that. You could do it with a resistor, but that would drop the voltage, which is bad for the loads, so no inverter or BMS has any feature to limit current. They can only either serve the load it's demand or shut off if they can't, and that's what they do.

 

[Ampster]

You can't throttle current.

That explains the concept in a few simple words. To be clear, some people call the device on the floor of my EV a throttle but it most likely is a potentiometer or transfucer which sends a signal to the inverter controlling the motors driving the wheels.

 

[hwy17]

That explains the concept in a few simple words.

I wanted to keep it simple but I just couldn't help but edit and add more words! We're hopeless.

There's always an if and or but in electrical, so the complexity of the debate always spirals out of control and you have to defensively complexify.

 

[houseofancients]

That explains the concept in a few simple words.

And not entirely true.
You can , and many BMS's do ( again see manual active current limit), however, this needs to be done by hardware on the BMS ( works the same as inrush limiter), and therefor in reasonability is limited to lower currents ( in most cases/BMS's 10a)

When talking about 10+ a , it becomes an entirely different ballgame, and BMS hardware ( and cooling) is simply not up to the task, and thus should be handled by the inverter(s)

 

[Ampster]

When talking about 10+ a , it becomes an entirely different ballgame

Yes that may be an exception to what I have mentioned above. To some extent, some power supply circuits do the same thing but they are not BMSs monitoring a current source like a BMS does.

 

[hwy17]

And not entirely true.
You can , and many BMS's do ( again see manual active current limit), however, this needs to be done by hardware on the BMS ( works the same as inrush limiter), and therefor in reasonability is limited to lower currents ( in most cases/BMS's 10a)

When talking about 10+ a , it becomes an entirely different ballgame, and BMS hardware ( and cooling) is simply not up to the task, and thus should be handled by the inverter(s)

I am confused by how that would work or what load it would work with. A precharge resistor is a resistor you wouldn't want to leave a resistor in a circuit it would make a heater.

 

[RHTizzy]

Current regulators can be used for high-power circuits, including those requiring more than 10A of current. For instance, the LT1970 op amp with variable current limiting is designed to protect high-power circuits by providing precise current limiting. Additionally, there are regulators available for higher currents which can be used with appropriate heatsinking and additional components. While the design of current regulators for high-power applications can be complex, advancements in technology, such as wide bandgap semiconductors and digital control techniques, are driving innovation in this area. Therefore, current regulators are indeed applicable to high-power circuits, providing essential protection and stability.

 

[Ampster]

Current regulators can be used for high-power circuits, including those requiring more than 10A of current. For instance, the LT1970 op amp with variable current limiting is designed to protect high-power circuits by providing precise current limiting. Additionally, there are regulators available for higher currents which can be used with appropriate heatsinking and additional components. While the design of current regulators for high-power applications can be complex, advancements in technology, such as wide bandgap semiconductors and digital control techniques, are driving innovation in this area. Therefore, current regulators are indeed applicable to high-power circuits, providing essential protection and stability.

Nothing new there. Power supplies and chargers have been doing that for years. The point of most of the comments on this thread is BMS designs have for the most part not incorporated that circuitry for multiple reasons, many of which have already been stated. I am perfectly happy letting my hybrid inverter do that job since that is where I want to have the control over current going into and going out of my batteries..I do use closed communications and let my BMS communicate to my inverter when to ramp down charging current because my BMS has more accurate voltage and SOC measurements and my inverter already has the circuitry for limiting current.

By the way, Chinese Spring Festival ends on February 15th so after that you should be able to contact the Chinese Engineers. My word of caution, having been married to a Chinese woman for ten years, there is a lot that is lost in translation.

 

[RHTizzy]

Nihao! Love your habit for disclaimers btw, some people think they have the sole right to intelligence and dont mind bullying others with their ignorance and hubris. Much appreciated that you display a mind of your own and are still willing to output goodwill for the sake of factual truth. Some might use the phrase "weasel words" but they misunderstand the importance of non comittal phrasing. I for one am happy that you are one of the few that dont mind being generous with your boundaries when stating facts.

 

[Ampster]

Love your habit for disclaimers btw, some people think they have the sole right to intelligence and dont mind bullying others with their ignorance and hubris.

I had no expectation of changing your mind about the need for a BMS which could control current. My comments are for the benefit of other readers who may wish to see another perspective. I joined this forum to learn from others with the expectation that I would then share any knowledge gained in that process with others. That is the value of these type of exchanges.

There is a reason in the marketplace why no one has developed such a product except as pointed out in cases of low current devices. DC to DC converters can also control current, but they do not do what inverters accomplish.

My apologies if you felt bullied. Perhaps we do not share the same goals and your purpose for participating is different than mine. I have reached the same conclusion @houseofancients did, and will ignore your comments in the future.