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enter image description hereI'm currently working on a project that will (hopefully) incentive people to stop using disposable batteries. To do that I'm thinking on creating a dummy battery that will allow you to plug a powerbank with the right voltage and, therefore, powering the device.

I want it to be as dummy proof as possible (no pun intended)

The problem lies on the correct power supply versus the number of batteries in a circuit.

For example, a 4x AA device requires 6V.

I'm trying to find a way of limiting people from plugging a 9V power supply on that case... Or even getting the battery to correct the voltage automatically in a easy way. Is there a simple circuit that would allow me to "sense", in a more or less passive way, how many batteries there are in the circuit?

Do you have any idea on how I could acomplish that?

Thank you

To clarify, Imagine the picture below. I want the smart battery to "sense" how many dummies are attached to it. This is a 4xAA example but it could be a 2x or even 6x batteries. (Diodes are just an attempt to prevent reverse polarity)

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  • \$\begingroup\$ Welcome to EE.SE! Please draw a schematic of what you are proposing. \$\endgroup\$ – winny May 13 '19 at 9:53
  • \$\begingroup\$ "Is there a simple circuit that would allow me to "sense", in a more or less passive way, how many batteries there are in the circuit?" No. But if your "dummy" battery is physically, e.g., AA sized it is safe to assume it should never output more than 1.5V. \$\endgroup\$ – JimmyB May 13 '19 at 11:00
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    \$\begingroup\$ "To do that I'm thinking on creating a dummy battery that will allow you to plug a powerbank with the right voltage and, therefore, powering the device." - What's wrong about existing rechargeable (AA,...) batteries? \$\endgroup\$ – JimmyB May 13 '19 at 11:02
  • \$\begingroup\$ Hi @winny, thank you! I've edited the post with a hand drawn picture of what I intend. Its not a circuit schematic since I have no idea on how I could make it without having to add another wire going through the batteries... \$\endgroup\$ – João Lima May 14 '19 at 14:42
  • \$\begingroup\$ Hi @JimmyB, Thanks for your answer. Yes, its safe to asume that. The only question is that there will only be a DC connector allowing you to use from 3V (for 2xAA) to 9V(6xAA)... I want to prevent people from damaging their devices by connecting a 9V PSU on a 2xAA device Regarding the existing rechargeable batteries, their capacity is arround 2000-3000mAh... How much nicer would be to have twice or even 10 times more autonomy? \$\endgroup\$ – João Lima May 14 '19 at 14:44

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