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I'm starting to experiment with small solar panel and wind turbines to get my head round what's involved in getting from sun/wind to stored electricity.

I have a 12V version of the opamp and transistor current source part of this schematic on a breadboard and plugged into a cheap, generic solar panel charge controller charging a 12V battery and as far as I can tell it's basically working as expected.

I would like to increase the battery and input voltages to 24V - but I need to have a better idea of how this circuit is working and what the component limitations are before I do that.

Right now my technical knowledge stops just after "If it's not too hot to touch it's working."

Given this very basic schematic - which doesn't include the charge controller and attempts a basic lead-acid battery - I'd appreciate any advice on what parts of this I should be measuring to check against data sheets or where it could be improved or any potential issues - both in the sim and on the breadboard.

Thank you!

Current Source v0.3

Edit: Updated the schematic to try and include the solar panel charge controller

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    \$\begingroup\$ You can model a battery as a (very) large capacitor with a series resistance and get pretty close to true behavior, however, you also have actual batteries shown in the circuit. Do one or the other. \$\endgroup\$ Apr 5, 2023 at 14:35
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    \$\begingroup\$ That would be batteries charging the batteries? Sorry, I'm having a hard time following you. Do you intend to have the solar/wind charge the batteries? Or have the batteries take over when solar/wind isn't present? \$\endgroup\$ Apr 5, 2023 at 14:37
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    \$\begingroup\$ If you are trying to charge the batteries via wind/solar, where you have +30V marked (on the collector of Q1) should be coming from the solar panels or wind turbines. This is the current that will be going to your batteries. \$\endgroup\$ Apr 5, 2023 at 14:39
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    \$\begingroup\$ In other words, the power from your renewables is not making it through the opamp. I think a better starting point would be to simply "diode-OR" your two renewables into the battery node. Whichever one is at a higher voltage (in each instant) will win and transfer its power to the battery, so if you want both at the same time you need some more complicated circuitry to achieve that. \$\endgroup\$
    – Ste Kulov
    Apr 7, 2023 at 1:56
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    \$\begingroup\$ I found some other questions on this site which pertain to the same thing you're trying to do. Maybe the information can help you: electronics.stackexchange.com/questions/524680 electronics.stackexchange.com/questions/158799 electronics.stackexchange.com/questions/207830 \$\endgroup\$
    – Ste Kulov
    Apr 7, 2023 at 20:53

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