Redmi power bank parallel connection

[maker_g8gk9haf_1661861357]

I have a Redmi 10,000 maH dual port power bank, and a Redmi 20,000 maH dual port power bank. I have used both of these, individually, to power a security camera inside my car. They both worked fine with that device. The 20,000 maH power bank was able to keep my security camera running for 4 days.
Could I connect the 2 together, in parallel, to give me higher maH, to power the camera longer, say 5 days? I would use a "Y" fitting, connecting the 10,000 maH output to the 20,000 maH output, and then the combined, single, output would go to my device. My understanding is that this would not affect voltage, only increase maH. Thanks.

 

[Harald Kapp]

My understanding is that this would not affect voltage, only increase maH. Thanks.

If it worked, it would not affect voltage but maH, that's the reason one would do it. However, there's a catch: It will not work without additional circuitry. The voltage from both power banks will not be exactly equal. Thus the one with a slightly higher output voltage will try to backdrive power into the other power bank. They are not made for it.
The circuit you need is called a power system oring circuit (link). Diodes can be used but incur a voltage drop. Dedicated controllers using MOSFETs also exist (example link).

 

[maker_g8gk9haf_1661861357]

If it worked, it would not affect voltage but maH, that's the reason one would do it. However, there's a catch: It will not work without additional circuitry. The voltage from both power banks will not be exactly equal. Thus the one with a slightly higher output voltage will try to backdrive power into the other power bank. They are not made for it.
The circuit you need is called a power system oring circuit (link). Diodes can be used but incur a voltage drop. Dedicated controllers using MOSFETs also exist (example link).

Thanks. I have very limited electronics experience. You are saying that power travels through a line of weak resistance. If I connect the 2 devices, the 20KmAH power would travel through its' output, and go into the 10K maH unit, because there is little resistance? And that may "fry" the output circuitry of the 10K unit? (The power of the 20K unit would enter the 10K unit through its' output port?) Those links that you gave, is there a device that I can buy on Amazon or somewhere that will easily allow me to plug the device into wherever it needs to go on my 2 Redmi units?

 

[maker_g8gk9haf_1661861357]

If it worked, it would not affect voltage but maH, that's the reason one would do it. However, there's a catch: It will not work without additional circuitry. The voltage from both power banks will not be exactly equal. Thus the one with a slightly higher output voltage will try to backdrive power into the other power bank. They are not made for it.
The circuit you need is called a power system oring circuit (link). Diodes can be used but incur a voltage drop. Dedicated controllers using MOSFETs also exist (example link).

Just for full disclosure. I have a Zetta Z82z camera in my car. I have a 20K maH Redmi power bank , also in my car. So, I have the Redmi power bank, connected to a Zetta ZA1 Power Bank reactivator, which is then connected to my camera.

(ZA-1 powerbank in the market will go into sleep when device under charging
is fully charged. There is no way to activate the powerbank to charge
out again even when the device needs power, unless you press the
power key on the powerbank. This makes continuous power supply
to the device impossible.

The ZA1 powerbank re-activator is designed to wake up the powerbank
every 2 hours, to keep it to continuously charge out.

I planned to connect the 2 power banks together with a "Y" cable, that would then connect to the reactivator, which would connect to the camera.
But, you are saying that it would not work, without that special circuity that you linked to in your answer. Thanks.

 

[maker_g8gk9haf_1661861357]

What happens when connecting two batteries of different amp-hour rating in parallel?

If it worked, it would not affect voltage but maH, that's the reason one would do it. However, there's a catch: It will not work without additional circuitry. The voltage from both power banks will not be exactly equal. Thus the one with a slightly higher output voltage will try to backdrive power into the other power bank. They are not made for it.
The circuit you need is called a power system oring circuit (link). Diodes can be used but incur a voltage drop. Dedicated controllers using MOSFETs also exist (example link).

https://www.quora.com/profile/Barry-Hunter-6

If it worked, it would not affect voltage but maH, that's the reason one would do it. However, there's a catch: It will not work without additional circuitry. The voltage from both power banks will not be exactly equal. Thus the one with a slightly higher output voltage will try to backdrive power into the other power bank. They are not made for it.
The circuit you need is called a power system oring circuit (link). Diodes can be used but incur a voltage drop. Dedicated controllers using MOSFETs also exist (example link).

Please respond. I asked on Quora, and this is one reply I received. Is this correct? I have 2 Redmi power banks, one 10K maH and the other 20K maH. They were both purchased about 1 month apart, and are the same type and configuration (dual port, same type batteries).

"As long as they are the same type of battery there are no problems. Don’t mix FLA, AGM or gel batteries in a parallel set up. They have different charge and discharge profiles.
They will charge and discharge according to capacities. A far as charging is concerned there is no problem because batteries are controlled by their voltage which will always be equal in a parallel set up. The same with discharge. The charger and the load don’ t count the number of cells."

Thank you.

 

[Harald Kapp]

The answer you got misses the point:

• Batteries are different from power banks. Batteries of the same type and voltage (not necessarily same mAh) can be used in parallel. The internal resistance of the batteries will provide the required voltage drop to distribute the current to the load between the two sources. It is done regularly. Also batteries usually tolerat a small amount of reverse current (how much depends on the type and quality of the battery).
• Power banks on the other hand have an internal battery (lithium) providing usually ~4 V which is stepped up to 5 V. The outputs of the step up regulators are usually not tolerant too reverse current.