Hi ,
For testing the BMS I want to design the 24-channel Li-ion battery cell simulator
In starting my thought was to use a potentiometer-based resistive divider network but facing problem of voltage geting chage if i chage resistance of one channel.
my requirment is to get voltage range form 2.8 to 4 in each channel individualy i want to change.

can any one suggest or Help me to design the circuit to simulate voltage sensing to BMS.

 

t is to get voltage range form 2.8 to 4 in each channel individualy i want to change.

The why not use 24 voltage sources (V) in series?
That way each can be changed individually without affecting the others.

 

The why not use 24 voltage sources (V) in series?
That way each can be changed individually without affecting the others.

Actually I want to create 2.8v to 4v in each channel from 100v power supply

and one channel ground should be common to next channel positive terminal for BMS voltage sensing

and it not possible to arrange on bench level 24 voltage source

 

Actually I want to create 2.8v to 4v in each channel from 100v power supply

Okay, I thought you were talking about a simulation.

If you can adjust the 100V supply to generate a constant-current, then you can vary one resistor value without affecting the voltage drop across the other series resistors.
What supply are you using?

 

Exactly i want to vary one resistor without affecting other channel voltage
I am using EA variable DC-power supply with 10A current rating
would you suggest how can I design circuit? which can satisfy above consition.

 

You may find this TI documentation helpful: https://www.ti.com/lit/an/slva618/s...98744&ref_url=https%3A%2F%2Fwww.google.com%2F

 

I am using EA variable DC-power supply with 10A current rating

That doesn't tell me much.
What are its specifications and adjustment range (current and voltage)?
Can you post a reference to it?

would you suggest how can I design circuit? which can satisfy above consition.

As soon as you post the details about the supply.

 

That doesn't tell me much.
What are its specifications and adjustment range (current and voltage)?
Can you post a reference to it?
As soon as you post the details about the supply.

I am using EA programmable DC power supply

https://elektroautomatik.com/shop/e...3/laboratory-power-supply-0..80v/0..50a?c=614

 

You may find this TI documentation helpful: https://www.ti.com/lit/an/slva618/slva618.pdf?ts=1721147798744&ref_url=https%3A%2F%2Fwww.google.com%2F

i have checked the circuit that one is not satisfy my conditions it is only for one channel but I want to create for 24 channel

 

I am using EA programmable DC power supply

https://elektroautomatik.com/shop/e...3/laboratory-power-supply-0..80v/0..50a?c=614

That is an 80V supply.
How will you get 100V?

 

That is an 80V supply.
How will you get 100V?

2 I will use in series

 

2 I will use in series

Okay.
That makes a constant-current approach problematic.

So how about applying 96V to twenty-four 10k pots in series (below).
If you take the voltage from the wiper, then adjustment of that wiper position from 0 to 4V, won't affect the current or voltage of the other pots.

 

Okay.
That makes a constant-current approach problematic.

So how about applying 96V to twenty-four 10k pots in series (below).
If you take the voltage from the wiper, then adjustment of that wiper position from 0 to 4V, won't affect the current or voltage of the other pots.

View attachment 327069

yes we try this circuit in hardware but this create problem if I change one channel pot value it will change voltage value in other channel as well. we want to vary each channel voltage individually.
also BMS showing voltage value up to 3 digit (x.xxx) so we don't want variation in voltage after decimal point.

 

Actually I want to create 2.8v to 4v in each channel from 100v power supply
and one channel ground should be common to next channel positive terminal for BMS voltage sensing

we don't want variation in voltage after decimal point.

You should use stabilized current in chain of resistors.

 

if I change one channel pot value it will change voltage value in other channel as well.

Not if you connect them as shown in post #12.
Unless there's a significant load on the pot wiper, the voltages on the other pots don't change if one pot voltage is changed.
In the LTspice sim below you can see that changing the voltage of the Ch2 pot wiper (yellow trace) has no effect on the other channel voltages.

 

This is only to test a simple "passive BMS" and analog adjustments with 24 pots & 24 Vdc readings. Is that right?

 

Not if you connect them as shown in post #12.
Unless there's a significant load on the pot wiper, the voltages on the other pots don't change if one pot voltage is changed.
In the LTspice sim below you can see that changing the voltage of the Ch2 pot wiper (yellow trace) has no effect on the other channel voltages.

View attachment 327095

we designed this in hardware in real time. We are not observing much change in the voltages of the far away channels from the channel we change.
If we change the Wiper-4 we are observing changes in wiper-3,wiper-5 dominantly, where as in all the other wipers the change is minimal.
And if we go for the wiper with larger resistance, we are unable to get a decently precise control over the voltages.

 

BMS showing voltage value up to 3 digit (x.xxx) so we don't want variation in voltage after decimal point.

And if we go for the wiper with larger resistance, we are unable to get a decently precise control over the voltages.

Improved circuit:
1. Minus of PS V1 and minus of resistors chain are grounded.
2. Value of stabilized current increased from 0.4 mA to 2.5 mA, so values of chain resistors are decreased.
3. Eliminated influence of base current of Q1 on resistors chain current accuracy.

Ultimate deviation of channel voltage in process of manipulation:
When all resistors from U2 to U24 are in state T=0, then
-If state of U1=0 then voltage of channel 1 is 2.745491 V
-if state of U1=1 then voltage of channel 1 is 4.016416 V
When all resistors from U2 to U24 are in state T=1, then
-If state of U1=0 then voltage of channel 1 is 2.745482 V
-If state of U1=1 then voltage of channel 1 is 4.016406 V

 

If we change the Wiper-4 we are observing changes in wiper-3,wiper-5 dominantly,

How exactly are the three terminals of the pots connected?

 

With that chain of pots, any reasonable current draw from wiper to next pot down will affect voltages at each pot... Its not simulating a stack of cells because in a cell stack the top of cell n is the bottom of cell n+1, whereas here the wiper of pot n isn't connected to the bottom of pot n+1.