How to design a circuit with two/three power sources with auto switching functionality between sourc

Thread Starter

nani2019

Joined Oct 10, 2019
10
Hi,

I am looking for a help in building a circuit with two/three power sources (DC), circuit should be able to select only one power source at time, until power source is drained i.e. less than certain voltage (5 volts) and swicth to draw power from other power source which has voltage more than 8 volts from rest of the power sources ( one at a time), and drained power sources or lesser voltage sources should be cut off from circuit, unless they have full voltage supply i.e drained source should be automatically redirected to re-charge.

Can anyone help with is requirement.


Regards,
Nani
 

dl324

Joined Mar 30, 2015
8,958
I am new to this stuff, please suggest a best and durable solution
Best is a subjective term and it's unlikely that someone will design something for you. Assistance is free, but not many will work for free.

Can a microcontroller be used?
 

djsfantasi

Joined Apr 11, 2010
5,617
Why do you have these requirements? Are you trying to continuously power a device without having to worry about running out of battery power? Or is it something else?

Why are you resorting to such a complicated design? A simpler approach might be to charge each source with their own battery management solution and diode OR the power from the sources to the load. But it all depends on why you came up with the original requirements.
 

Thread Starter

nani2019

Joined Oct 10, 2019
10
Why do you have these requirements? Are you trying to continuously power a device without having to worry about running out of battery power? Or is it something else?

Why are you resorting to such a complicated design? A simpler approach might be to charge each source with their own battery management solution and diode OR the power from the sources to the load. But it all depends on why you came up with the original requirements.
Hi, Yes, I have to continuously power a device, without running out of battery power, could please eloborate your solution for this requirement.
 

KMoffett

Joined Dec 19, 2007
2,770
Microcontroller with:
uC Supply voltage regulator output lower than the lowest battery voltage (likely 3.3VDC)
uC voltage regulators' inputs diode-OR'd to all three batteries
3 analog inputs from the batteries to monitor voltage levels
3 digital outputs to SPDT relays to switch each battery between load and charger circuit
Where are the chargers getting their power?
 

djsfantasi

Joined Apr 11, 2010
5,617
Hi, Yes, I have to continuously power a device, without running out of battery power, could please eloborate your solution for this requirement.
DodgyDave explained it already.

And I suggest you question your assumptions. Why do you have to redirect the lower voltage source to charge automatically? Why not set up all sources to charge when their capacity falls below a certain point? I don’t see “redirection” as a valid requirement.
 

Thread Starter

nani2019

Joined Oct 10, 2019
10
Microcontroller with:
uC Supply voltage regulator output lower than the lowest battery voltage (likely 3.3VDC)
uC voltage regulators' inputs diode-OR'd to all three batteries
3 analog inputs from the batteries to monitor voltage levels
3 digital outputs to SPDT relays to switch each battery between load and charger circuit
Where are the chargers getting their power?
charging power source is a solar panel/wind turbine
 

Thread Starter

nani2019

Joined Oct 10, 2019
10
DodgyDave explained it already.

And I suggest you question your assumptions. Why do you have to redirect the lower voltage source to charge automatically? Why not set up all sources to charge when their capacity falls below a certain point? I don’t see “redirection” as a valid requirement.
Load should be running continuously, with one battery at least rest discharged battery should be put back to charging
 

Thread Starter

nani2019

Joined Oct 10, 2019
10
Then you can use a microcontroller to switch the load between batteries and the batteries to chargers.

If you having a charging source available, why don't you just use it? We need many more details.
Charging source is a wind turbine/ solar panel, drained battery should be charged by this power source, charged battery will be powering the load.
 

djsfantasi

Joined Apr 11, 2010
5,617
Load should be running continuously, with one battery at least rest discharged battery should be put back to charging
You kind of answered my question. You’ve chosen to redirect the charging because you don’t understand how to do this otherwise, regardless of what people say. That’s why I suggested that you challenge your assumptions.

I’m out (mostly)!
 

djsfantasi

Joined Apr 11, 2010
5,617
I see no advantage for having 3 batteries over just having one larger battery. :confused:
It is common to charge a battery while it's under load.
No need for the complexity of more than one.
See? ...what @crutschow said.

When I meant to challenge your assumptions, is that you said:
Load should be running continuously, with one battery at least rest discharged battery should be put back to charging
Challenging that statement, I come up with;
Load must run continuously. When necessary. a battery supply should be recharged until the battery is full.
IMHO, your requirement is:
The load should run continuously. Power is supplied by a battery/batteries which is/are recharged to maintain its output voltage.
These requirements make no assumption about the number of batteries nor switching. That problem statement is exactly what is required, with no assumptions of the design. Your more detailed concept satisfies this requirement, as well as a design including a larger battery (or battery pack!) which is always connected to a charging source with a battery management system.
 

Thread Starter

nani2019

Joined Oct 10, 2019
10
See? ...what @crutschow said.

When I meant to challenge your assumptions, is that you said:


Challenging that statement, I come up with;


IMHO, your requirement is:


These requirements make no assumption about the number of batteries nor switching. That problem statement is exactly what is required, with no assumptions of the design. Your more detailed concept satisfies this requirement, as well as a design including a larger battery (or battery pack!) which is always connected to a charging source with a battery management system.
Can I use capacitors instead of battery pack?
 
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