BMS that can regulate voltage and current?

[squowse]

Had a couple people on Facebook groups insistent that there are battery systems that come with a BMS that can manage the charging voltage and current.
Anyone else come across these?

Seems like they must have a DC-DC converter like a B2B charger.

Renogy was one mentioned, but all I find is sales waffle about new generation super smart bms etc etc.

Specifically mentioned was a battery that had a bms that (apparently) charged at a constant 70A all the way to 98%. I'm aware that's not necessarily recommended but I believe it would require the charging voltage to be raised to 15V or more, and then quickly dropped off to avoid raising the cell voltages above 3.65v as it became full.

This is built into the battery apparently.

I'm not sure what's going on tbh. I'm surprised I haven't heard about these in more detail if they do exist.

My suspicion is that users are being led along by sales waffle

Please shine a light.

 

[100 Proof]

That's not the purpose of a BMS. The batteries they're talking about may have a BMS *AND* a charge controller baked into it.

Of course, if there's something new out there that I'm not aware of, I'm happy to be wrong.

 

[Ampster]

BMS that can manage the charging voltage and current.

It may be a marketing term as @squowse suggested. Most BMSs can shut off charging and discharging based on voltage or current. If that is what they are referring to that may be the extent of what they "manage". On the otherhand most EV BMSs can communicate with chargers and send signals that can cause the charger to vary voltage and current.

 

[Hedges]

I think BMS can request those parameters be regulated.
For instance REC BMS talking to Sunny Island.
This should let voltage be held low enough that current into cells remains within balancing limits, letting BMS do its job.

The BMS has voltage and current measurement. Also either resistive bleed-off of a few mA, or small switching power supply for active balancing (or I think active balancer usually sold as a separate product.)
The inverter/charger has switching supplies able to source/sink 10's to 100's of amps.

 

[Bob B]

Chargery has a setup where their power supply will communicate with their BMS .... don't know of anyone that has ever tested it.

 

[squowse]

That's not the purpose of a BMS. The batteries they're talking about may have a BMS *AND* a charge controller baked into it.

Of course, if there's something new out there that I'm not aware of, I'm happy to be wrong.

Yes. The only link I've had so far is to a Renogy battery with "smart bms". The user was insistent that their battery managed the charging process and kept 70A steady charge up to 98% regardless of supplied voltage or current (sic). Then tapered down to zero between 98 and 100%. He reckoned this "active bms" technology had been implemented by"dozens of manufacturers ".
Another user saying that "drop in" lithium batteries could be charged directly from vehicle alternator as they managed the charging voltage themselves.

I'm sceptical to say the least. And if they exist I'm surprised no one here knows about them. I'm not talking about high end custom BMS, these are supposedly consumer products.

 

[Steve_S]

Had a couple people on Facebook groups insistent that there are battery systems that come with a BMS that can manage the charging voltage and current.

A nugget that reappears once in a while. Gotta love it when folks read 1/2 a thing, make assumptions and come up with these conclusions... Thank goodness these folks are not Doctors... (although some, I kinda wonder).

Basically, these people ASSUME that each cell is an independent battery and treated as such. Imagine the HARDWARE required to have essentially a full on BMS per CELL that can not only manage it but regulate Amps IN/OUT... Nasty enough for a simple 4S,8S,16S but what about bigger packs ? Simply put "Ludicrous".... The cost of the electronics alone would outweigh the cost of the cells, then the amount of electronics and it's weight too.... this is where the ridiculousness becomes even more apparent.

FaceBlot = Source of Twisted Entertainment.... Beware of the FacePox Vacuum that absconds your soul & mind. Free Yourself and DE-Pox Now !

 

[Hedges]

Another user saying that "drop in" lithium batteries could be charged directly from vehicle alternator as they managed the charging voltage themselves.

Of course, the cells do manage charging current themselves. Same for lead-acid. Current tapers off as voltage approaches CV limit of source.
Just need a battery able to handle max voltage alternator would put out (even when regulator adjusts upward on a cold day.) And an alternator able to current-limit or otherwise handle the battery's low internal resistance and high current acceptance.

Imagine the HARDWARE required to have essentially a full on BMS per CELL that can not only manage it but regulate Amps IN/OUT... Nasty enough for a simple 4S,8S,16S but what about bigger packs ? Simply put "Ludicrous".... The cost of the electronics alone would outweigh the cost of the cells, then the amount of electronics and it's weight too.... this is where the ridiculousness becomes even more apparent.

Maybe could be done with a linear regulator. Just one needed for the series-connected cells. Dropping voltage across a transistor, less voltage on cells so less current drawn. Temperature-limit by increasing voltage drop further until current is so low the power dissipation drops enough. This of course would kick in only when near full and passive balancing has to occur.

"Ideal diode" to allow discharge current (or disconnect for low voltage.)

Imagine something as silly as putting a GT PV inverter on every single PV panel, complete with MPPT, UL-1741, etc.
When all that complexity and cost could be done just once, with a series/parallel PV array connected to it.

The cost of the electronics alone would outweigh the cost of the cells

Enphase IQ7PLUS-72-2-US 235W-440W+ Micro Inverter

Enphase 235W-350W+ Micro Inverter IQ7-60-2-US at SolarTown.com - Shop our collection of Solar products from top brands like LG, Enphase, SolarEdge and many more!

solartown.com

Mission Solar 310W 72 Cell MSE310SB1A | SanTan Solar

store.santansolar.com

Back at a certain EMS I used to work for, a boss wanted to get into the solar industry. They had taken over or built factories for many major customers. I suggested they approach SMA and offer to build their products. (At the time SMA had > 50% of all GT PV business, at least in California. Some 20 other vendors together shared the remaining < 50%, according to CEC list of installations.)

He asked, "Why not design our own inverter?" (At the time, the Trace model after getting a number of installations was found to not comply correctly with UL-1741)

He also asked, "Why not implement an inverter on each photovoltaic wafer?"

 

[time2roll]

Stay away from FB for any technical information. No source was posted or equipment model numbers right???? I thought so.
The FB poster probably does not even know that Ohm, Ampere and Volta were actual people.

 

[squowse]

Stay away from FB for any technical information. No source was posted or equipment model numbers right???? I thought so.
The FB poster probably does not even know that Ohm, Ampere and Volta were actual people.

There was a link to a renogy battery (in German) and another battery website in Germany. Google translate did say "charge control" but that's not very convincing. The poster was insistent they got 70A right up to 98%. Would a b2b charger do that? Not unless it had communication with the bms

 

[jasonhc73]

BMSes are like Mall Cops.

They can observe and report the voltage and amps.
And they can lock the doors, I mean turn off the battery IF it has a direct connection and control of a relay.

Some have "Passive Balancing", which just means when one cell is over-voltage, it gets a small load applied to try to lower its voltage to that cell.

That is it.

 

[squowse]

BMSes are like Mall Cops.

They can observe and report the voltage and amps.
And they can lock the doors, I mean turn off the battery IF it has a direct connection and control of a relay.

Some have "Passive Balancing", which just means when one cell is over-voltage, it gets a small load applied to try to lower its voltage to that cell.

That is it.

Yeah I know this. I'm just asking if anyone else heard of a bms that can control the voltage as well. It's not beyond imagination or technical ability but i don't think it exists in a consumer product.

 

[shavermcspud]

The seplos BMS unit does do all of those things, it can request current tail off toward the end of the charge, voltage output etc.

 

[Ampster]

The seplos BMS unit does do all of those things, it can request current tail off toward the end of the charge,

My BMS can request those things too but if it does not have a compatible charger the request is useless. Instead it triggers the contactor to open if voltage gets above the HVD setting.

 

[time2roll]

There was a link to a renogy battery (in German) and another battery website in Germany. Google translate did say "charge control" but that's not very convincing. The poster was insistent they got 70A right up to 98%. Would a b2b charger do that? Not unless it had communication with the bms

If it was a 70 amp charger close to the battery suppling full voltage I could see it going flat out to 98%. However it is the charger managing the voltage and current. Put a 200 amp charger on it at 50% higher voltage and see what is regulated by the BMS.

 

[jasonhc73]

The seplos BMS unit does do all of those things, it can request current tail off toward the end of the charge, voltage output etc.

Please provide a link to this BMS.

 

[Ampster]

Please provide a link to this BMS

Google is your friend. Here is a link to the manual download.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://diysolarforum.com/resources/seplos-48v-200a-8s-16s-bms.218/download&ved=2ahUKEwiyqrPX0OPzAhVWHzQIHcoMAwYQFnoECAMQAQ&usg=AOvVaw02Kt3O3_VTJD5P2S_Byd68

 

[shavermcspud]

My BMS can request those things too but if it does not have a compatible charger the request is useless. Instead it triggers the contactor to open if voltage gets above the HVD setting.

Its compatible with around 10 different makes of inverter

 

[Ampster]

Its compatible with around 10 different makes of inverter

Compatible with? I could say that my Orion BMS is compatible with 100% of inverters because it will disconnect battery at HVD. Perhaps that is the definition of "regulate" in the title of this thread.

 

[jasonhc73]

The seplos BMS unit does do all of those things, it can request current tail off toward the end of the charge, voltage output etc.

Can you point out in the manual where it regulates the voltage?
All I see is on and off. I guess on and off is regulating between what it is and zero. But making 3.65V from 3.3V or 3.9V is not part of it's capability.