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I am using a LiFePo4 battery 26.5 V, 18 Ah in my project where I am using three DC motors

I need a constant voltage for my motors but as the load on one of the motors increases it affects the speed of the other motors in the circuit.

I tried regulating the voltage for the one motor using a 7824 voltage regulator, so after regulating I am not facing the problem for that motor, but in actual conditions the peak current of the motors will be 5 A so I want to regulate it to 24 V, 5 A.

Is there any regulator circuit by which I can get the constant output of 24 V up to 5 A?

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  • \$\begingroup\$ Does that mean 15 amps peak for all three motors? Have you considered regulation for each motor? Do you have speed feedback from the motors? \$\endgroup\$
    – Andy aka
    Commented Jan 8, 2022 at 10:43
  • \$\begingroup\$ @Andyaka Yes I want to regulate for each motor and yes I am using encoders \$\endgroup\$
    – user274774
    Commented Jan 8, 2022 at 10:45
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    \$\begingroup\$ How do you control the speed for each motor? Do you use PWM or is it running flat out? \$\endgroup\$
    – Andy aka
    Commented Jan 8, 2022 at 10:47
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    \$\begingroup\$ So why not modify the PWM when you sense the speed is diminishing? \$\endgroup\$
    – Andy aka
    Commented Jan 8, 2022 at 10:49
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    \$\begingroup\$ "Fails to do that"-> is that with one motor running o 3 or? Is the battery capacity about 3Ah or 5 Ah or ??? What is the max current for EACH motor. YOU know all these things. WE don't. You need to explain the situation completely. Failure to do so will see your question closed (not by me). You have one close vote already. Please provide ALL data asap. We can answer the question IF we know what the question actually is. \$\endgroup\$
    – Russell McMahon ♦
    Commented Jan 8, 2022 at 11:02

2 Answers 2

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If a voltage regulator was the only feasible solution I'd be looking at a low-drop-out buck regulator like the one below using the LT8638S (for example): -

enter image description here

The example circuit above is for a 12 volt regulator but it looks like it should be good for a 24 volt output at up to 5 amps without much trouble.

I'm not recommending that device in particularly (although it looks like it's a good match); I'm recommending a low-drop-out buck regulator and there are many offerings from Analog Devices and TI to choose from. The benefit is that you get high efficiency (circa 90%) and low drop-out.

The other option is (given that you have PWM control over the motor) is to use a boost regulator to provide you with about 30 volts. The LTC7841 appears to be a reasonable match: -

enter image description here

It should be able to work with a supply from below 20 volts to 28 volts and produce a 30 volts output. This will ensure that this situation might be avoided i.e. it provides enough voltage overhead to overcome this problem: -

@Andyaka it has to run on a 15 degrees inclined and declined surface but it fails to do that even after full PWM signal

I have some suspicions that on a 24 volt supply it may fail to do what you expect it to do (as per the above comment) and so, using a boost regulator (like the one above) is probably something you need to consider. Or, maybe the LTC7804: -

enter image description here

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It is not possible to draw 5A with a 7824. In addition, it is not possible to regulate with just 1.8 V more. These regulators have a dropout limit of 2 V (typical.) Incidentally, series regulators are the worst choice as the excess voltage has to be dissipated as heat.

Perhaps you can proceed more skillfully and not regulate the voltage, as this should be sufficiently precise, but the current flow depending on the speed. The back EMF can be evaluated for this purpose.

Depending on the type, motors can be controlled with pulse width modulation. There are also numerous integrated components that can be used.

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