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Newton's third law problem.
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Circlotron:

--- Quote from: electrodacus on November 27, 2022, 04:41:59 pm ---If you apply no power the vehicle will be accelerated in the direction of the wind and you need to match that power in ideal case to stay at zero speed then you need extra in order to move upwind.

--- End quote ---
If you are staying at zero speed then no work is being expended. A force maybe, but if there is no movement then no power is being used.
electrodacus:

--- Quote from: Kleinstein on November 28, 2022, 08:38:51 am ---
--- Quote from: electrodacus on November 28, 2022, 02:29:29 am ---
It is like you connecting the positive input of a DC-DC converter to battery+ the negative of the battery is connected to earth the positive output of the DC-DC converter to earth and the negative input and output of the DC-DC converter connected to each other but nothing else and you expecting that DC-DC converter to do anything useful.

--- End quote ---

That configuration is a little unusual, but can still work if the DC/DC converter has a lower output than input voltage and can thus provide more current at the output than it needs at the input. It is not a very praktical (efficient) solution but it would still generate a negative voltage. With real world parts it may need so help to start up, depending how well the DCDC converter handles load to the output if there is no input drive.

--- End quote ---

Did you understood the setup ?
There are only to points connected on the DC-DC converter. The positive input and the positive output and nothing else.
Can you explain how you will get higher current at output than at the input ?
electrodacus:

--- Quote from: cbutlera on November 28, 2022, 09:15:30 am ---
I just tried it with an old Traco TEF2011 module that I found in my junk box, 10-30V in 5V out.  It needed an additional 5V power supply connected to the output to get it started, but once started the additional supply could be disconnected.  As expected it worked just fine, and even continued to run with the input power supply reduced to 2V, giving 7V across the converter input terminals.

--- End quote ---

Sorry but can you be more exact in describing your setup ?
You can of course have a voltage drop on the converter if you have a current flowing through the converter depending on the type of converter.
What you can not have is a higher voltage at output than input, a negative voltage or different current at output than at the input.
electrodacus:

--- Quote from: Circlotron on November 28, 2022, 11:03:15 am ---If you are staying at zero speed then no work is being expended. A force maybe, but if there is no movement then no power is being used.

--- End quote ---

Have you ever had an electric motor providing a force / torque without using energy ? Or even simpler an electromagnet providing a force without using energy.
Even you using your arm to provide a force will be using energy even tho there is no movement and yes that energy will be dissipated as heat.
 
Kleinstein:

--- Quote from: electrodacus on November 28, 2022, 04:56:20 pm ---
--- Quote from: Kleinstein on November 28, 2022, 08:38:51 am ---
--- Quote from: electrodacus on November 28, 2022, 02:29:29 am ---
It is like you connecting the positive input of a DC-DC converter to battery+ the negative of the battery is connected to earth the positive output of the DC-DC converter to earth and the negative input and output of the DC-DC converter connected to each other but nothing else and you expecting that DC-DC converter to do anything useful.

--- End quote ---

That configuration is a little unusual, but can still work if the DC/DC converter has a lower output than input voltage and can thus provide more current at the output than it needs at the input. It is not a very praktical (efficient) solution but it would still generate a negative voltage. With real world parts it may need so help to start up, depending how well the DCDC converter handles load to the output if there is no input drive.

--- End quote ---

Did you understood the setup ?
There are only to points connected on the DC-DC converter. The positive input and the positive output and nothing else.
Can you explain how you will get higher current at output than at the input ?

--- End quote ---

The effective input voltage see by the DC/DC converter is the sum of input voltage + output voltage (not considering a sign). So the available output current / load current between the DCDC converters outputs is the difference of the input current minus the output current.  So if the DCDC converter is something like a 24 V input to 6 V output type  with 75% efficiency one would have 3 times the ouput courrent at the DCDC converter an 2 times the output current from the input current. So one could get something like 18V 1A in and -6 V 2 A out.

There is nothing magic with the circuit - depending one the DCDC is may just need some help on start up.
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