For sensing I imagine one or two led's across each channel. They contain their own built-in voltage regulation. They serve as visual indicators. With safety resistors at each led you can adjust them individually.
Here i am not designing the BMSTo design anything you must have measurable specs. !
For a BMS , there are two states; charging and discharging.
1. For charging only OVP in each cell is needed while the string is regulated by CC/CV which must be specified.
2. For discharging, only UVP is needed to bypass loading on the weakest cell(s).
For simplicity let's consider specs for only 1.
Pls list all specs. The BMS will have a Pmax limit. for each cell.
I just want to simulate voltage for BMS and create UV and OV condition I don't want simulate charge, discharge and cell balancingWhat are asking specifically? An universal cell simulator has galvanic isolation for each channel, e.g. by DC/DC converter, isolated digital interface for setpoint transmission. Full featured cell simulator has impedance emulation and bidirectional current capability and is able to simulate charge, discharge and cell balancing. For your purposes, a programmable low power voltage source may be sufficient.
Here I am not doing battery modelingYou must outline the scope of your idea, purpose with functional requirements before any realization is possible. (not just 2.8 to 4.2 V)
This may help develop a plan.
Battery Management Systems (BMS)
Learn how to design and simulate battery management systems. Resources include videos, examples, and documentation covering motor modeling, control design, and automatic code generation.www.mathworks.com
Do you have models for good and bad cells with memory effects, ESRs and C values
* Circuit 1: U_out(1) = U_pot(1) + GND = U_pot(1) + 0V = U_pot(1)
* Circuit n: U_out = U_pot + U_out(n-1)
For what BMS?
Are you trying to test a BMS charger only? under load too?
How much current?
It seems you are trying to simulate a string of battery voltages over this voltage range without any thought of the memory effects of voltage (R1C2) and the ESR * capacity (R2C2) and assuming your future tests of using a linear voltage source of unknown impedance spectrum is good enough. Any BMS is a control system and will have ideal responses with a resistive programmable voltage source but possibly unknown effects with a highly reactive cell voltage.
So your end purpose is still unclear and makes a big difference.
I cant't afford boomy cell simulator its a costly one and also offer only 12 channel in one simulatorAre you wasting time with trial & error ideas when you should define your MUST-HAVE specs vs NICE-TO-HAVE specs.
Do you need 24 isolated voltage sources or non-isolated ones?
Do you need 4 digits of accuracy or 3? Then 10% pots are out of the question.
What input options are you limited to? Analog or digital or software controlled?
How fast do settings need to be changed?
What is your budget for time and $?
Will that be just for your education of profit ? Why not BUY vs MAKE?
Engineering Specs determine how to evaluate any design and make tradeoffs early.
would you explain more about this circuit how it is connected any model you have?Hi,
If I understand correctly you want to EMULATE individual cell voltages of cwlls connected in series.
If so I recommend to use a single voltage reference, feeding all the pots.
The pot output should feed individual OPAMP circuits that ADD the pot voltage to the output of the previous OPAMP circuit.
The first OPAMP obvioulsy has to reference to GND.
Circuits 1...n:
Code:* Circuit 1: U_out(1) = U_pot(1) + GND = U_pot(1) + 0V = U_pot(1) * Circuit n: U_out = U_pot + U_out(n-1)
Mind: the OPAMPs need a power supply that is higher than the maximum expectable output voltge
Klaus
but from adder ckt how we get from 100v to individual variable voltage for each cell channelHi,
did you do an internet search for "OPAMP ADDER circuit" or "OPAMP SUMMING circuit"?
Klaus
More than once at Edaboard, schematics from certain simulator programs have appeared, which contain several of the identical component. In a corner is drawn a single master component. Maybe a voltage source. All the identical components take their parameters from the master component. Change the master component's parameters, and you change all the other matching component parameters.I just want to create string of individual adjustable voltage with any one either isolated or non-isolated
I´v already answered:but from adder ckt how we get from 100v to individual variable voltage for each cell channel
Klaus he wants to simulate a string of 24 Li Cells and test various scenarios of mismatched voltages to see if a BMS does its job whatever that is ( no specs) except he demands 3 digits accuracy but doesn't say how he is going to measure it. To properly do this needs variable ESR and variable V and he is willing to neglect variable C. He has no functional user interface specs, no testable design specs, nada. Yet he wants a cheap battery string simulator. How will he know if any of the cells deviates from the 3 digit accuracy at any time? How much power must be absorbed in this bidirectional cell synth, he won't say. He has no battery model and no gives no answers to my questions on specs. Commercial 24 channel battery string simulators are more than $3k and are 3U 19" racks or more and do a lot more than what he wants. Yet he is unable to create a functional design spec. and does not understand he is supplying the power with no specs that must be aborbed in this battery string simulator. Each cell is basically 10kF and 50 mOhms = RC but real batteries have 3 series R||C values and the total ESR must absorb the load. Imagine 100W to be dissipated per Amp at 100V CV for the total string. No specs. Your idea might go poof. (lol)I´v already answered:
Mind: the OPAMPs need a power supply that is higher than the maximum expectable output voltge
And it should be obvious that you need an OPAMP capable of handling this high voltage. But that´s why there are selection tools to choose the right OPAMP.
So if you ask me for a different approach:
* you still need a power supply higher than the maximum expectable output.
* then place all your [pot with series resistor] in a string and supply them with a current source from the high rail.
But the output will be weak (high impedance) .. thus I wouldn´t be surprised if you need some kind of buffer. (Again: OPAMP?)
(We don´t know the load_current_range and expected accuracy ...)
***
It seems you somehow don´t like my answers. I´m a professinal electronics designer ... and my answers just show how I would solve the task.
Klaus
I understand post#8 differently:Klaus he wants to simulate a string of 24 Li Cells and test various scenarios of mismatched voltages to see if a BMS does its job whatever that is
I just want to simulate voltage for BMS and create UV and OV condition I don't want simulate charge, discharge and cell balancing
would you tell me how I create 24 channel for voltage sensing from programmable low power voltage source
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