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[MarkE]

Profitis, thanks. 

So the answer to 1) is that energy is needed to recharge.  Given that reversibility requires that a system can move between two states in either direction without expenditure of energy, it would seem then that the requirement for outside energy to move in the recharge direction means that the process is not thermodynamically reversible.   I think that reinforces rather than refutes the idea that the Nernst equation describes irreversible processes.

I ask that you provide further clarification to your answer to 2).  By "switching between 2 directions of entropy ...", do you mean to say that which way the battery goes depends on the external circumstances?

[profitis]

@mark E 1) wrong.you,re saying that the word reversability implies spontaneity which it doesnt.a nicad battery is totaly reversable but not spontaneously.it needs work input by you and me to recharge it.work by you and me isnt needed to recharge any karpen system,only a spontaneous reversability is needed,ie.a spontaneous heat-sink. Any voltage including nernst voltage says nothing about reversability,only about spontaneity of reaction.it is only kelvin statement that implies thermodynamic irreversability on everything,thats why its written in textbooks.if nernst equation told us everything about irreversability then kelvin statement wouldnt be needed. 2) only if the rate of discharge exceeds the rate of recharge is a switch needed and that can be powered by the battery itself,eg.transistor so no external influence is required for switching between on/off modes.the original karpen cell used a motor-switch to recharge inbetween discharge pulses.

[MarkE]

@mark E 1) wrong.you,re saying that the word reversability implies spontaneity which it doesnt.a nicad battery is totaly reversable but not spontaneously.it needs work input by you and me to recharge it.work by you and me isnt needed to recharge any karpen system,only a spontaneous reversability is needed,ie.a spontaneous heat-sink. Any voltage including nernst voltage says nothing about reversability,only about spontaneity of reaction.it is only kelvin statement that implies thermodynamic irreversability on everything,thats why its written in textbooks.if nernst equation told us everything about irreversability then kelvin statement wouldnt be needed. 2) only if the rate of discharge exceeds the rate of recharge is a switch needed and that can be powered by the battery itself,eg.transistor so no external influence is required for switching between on/off modes.the original karpen cell used a motor-switch to recharge inbetween discharge pulses.

Profitis, I said that reversibility requires that a system can traverse either direction between two states without external energy input.  Since the answer to question 1) is that external energy is required to go in the recharge direction, that system is thermodynamically irreversible.  No battery that I know of is thermodynamically reversible.  As you acknowledge with the NiCd external energy is required to recharge. 

There are numerous academic references that state that the Nernst equation at least implies irreversibility based on the Gibbs free energy. 

The Karpen battery's claimed properties are disputed.

I would as much as anyone else love to see a break through discovery in energy.  A macro scale violation of any of the laws of energy would certainly qualify.  That's going to take some rock solid evidence to prove. 

[profitis]

@mark E i can summerise the whole process like this: work isnt needed by the system to  spontaneously compress gas.a spontaneous heat-sink is needed.

[profitis]

@mark E.im going to answer your post just now..