The station that I operate continuously is a cabled station, yes. That doesn't mean I have no information about wireless stations.
Davis uses protective diodes in all power circuits. The (recent, at least) ISS is no exception.
No, I am not saying "higher voltage can't override lower voltage" - but please define "override".
And I don't know what Old Tele man means by "overrides".
Davis circuitry (based on diodes to prevent reverse-flow) allows the highest available voltage source to power the ISS. That just makes sense. They also protect the supercap from reasonable over-voltage conditions.
Having said that, yes, soldering wires to the battery holder will work - it's just more convenient to use the jack that Davis provided. [And the on-board battery could be left in, to provide an additional power source]
Given all that, I'm not sure what the purpose of your "hint" in your previous post was. I think it's pretty clear that by "override" it was meant that the power from the adapter would be used instead of the power from the solar cell/supercap. (Please don't ask me what "used" mean now.
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Does the circuit protection circuitry also protect the supercap from discharge when connected to a coil with a certain amount of internal impedance (such as an ac/dc adapter)?
As I mentioned before, yes he can leave the battery in the ISS, where it should last for years, whether or not the solar charging system still works with the adapter connected, assuming no frequent or prolonged power outages. But the whole purpose of his endeavor was to remove the battery from the ISS in the first place where he could easily replace it when needed. I've never had any experience with a lithium battery leaking or corroding, but I would still be wary about leaving it where I couldn't at least check it periodically. But that may just be me.
It may be slightlly more convenient to use the jack, but simply connecting wires to the ISS from an external battery holder would be a one time thing, and he would most likely need to extend the adapter, which itself would involve splicing. And before he uses the jack I would think he would want to know for sure that the ISS would keep transmitting in a power outage.
It sounds to me that the OP just wants to do what he asked about in the first place, but if he is interested in following the other suggestions, he would probably be well advised to do a little experimenting on his own while he has the station down and easily accessible.
As someone mentioned, a cabled station may have been better, assuming extra sensors, or the ability to move the console wasn't desired. So even if the battery is remoted, the wireless is still more flexible. But, while looking at all possibilities is good, I'm not really seeing what the big problem is with the OP's original idea.