• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 47 subscribers
  • Views 1142 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

OPA544: OPA544

Dave Whitaker
Prodigy 190 points

Part Number: OPA544
Other Parts Discussed in Thread: OPA549, OPA548,

Good afternoon,

I have been looking at the document entitled,  "Building Your Own Battery Simulator"    (Application Report SLVA618–October 2013) 
I  would like to make use of this idea ,   but my requirement would be to simulate a  Lead-Acid- chemistry battery  of either 12 volts or 24 volts (two  12 volt batteries in series) .
As I don't need to simulate the internal protection of a Lithium Ion battery  please explain how the circuit would  need to be modified for lead acid.

Also,   will this circuit work as is or is this just a very basic concept ?  If so,  would you be able to give more details about what might need to be added ?

Regards

Dave Whitaker 

  • 0
    TI__Guru* 77501 points

    Hi Dave,

    You may use SLVA618 Application Report with the slightly modification, mainly on the supply voltage rails. The application note is tailored for a single cell Li_ battery chargers, which includes battery charging and discharging cycles. 

    Since you want to place 12V or 24V battery in series for charging or discharging, you need to increase the op amp supply rails to +/-30Vdc to 35Vdc range. OPA544's output current is only rated approx. 2A or so. If you want to charge/discharge Pb battery at higher current rate, then you have to use other power amplifiers, such as OPA548 or OPA549.  If the application requires high source/sink current requirements, please let me know. 

    Unlike Li+ battery charging, Pb acid battery has the following charging characteristics (on top of my mind). 

    1. Typically constant voltage charging (though can be constant current charging as well). 

    2. Pb acid battery has larger leakage current. Battery charging temperature is not too critical without battery damage, 

    3. Three mode of charge 1. constant V (or constant I) charging 2. Constant Voltage charging 3. Trickle charging. (you may combine charging cycles 1 & 2 in one).

    4. Over voltage charging or under voltage discharging is not critical typically, for 12Vdc, typical 12Vdc < charging voltage < 14Vdc.  

    5. Pb acid can be discharged to depletion without battery damage. 

    6. Internal Zout impedance is larger than Li+ battery. 

    Here is the simulation that I would suggest: for constant voltage charging: I arbitrarily set Vbias = 6Vdc, which you can do whatever the application is called out. 

    /cfs-file/__key/communityserver-discussions-components-files/14/OPA544-Pb-Battery-Charging-09142020.TSC

    If you have any questions, please let us know. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 190 points

    Thanks Raymond,

    Please clarify ,   what is the Vcc  voltage in the bottom left of your schematic ?     33.5 V  ?

    Dave

  • 0 in reply to Dave Whitaker
    TI__Guru* 77501 points

    Hi Dave,

    Do you mean Vcc shown in the following schematic? I simply copied Figure 1 of the application note, where is 12Vdc. Since this is 35Vdc power rails, then you do not need to generate 12Vdc rail for the circuit (it was a little messy when I copied 35Vdc from the supply voltage, so I did this way. No additional intent). 

    Vcc at positive voltage rail is simply a name. Vcc here is  voltage node, which it may confuse you somewhat. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 190 points

    OK thanks Raymond.

    Dave