Quick reply...
Epic week? I will not get my N900 working earlier than this Friday. Because:
1. soldering the broken wires within the battery charger did not resolve the not-working problem;
1.0. attempts to solder the wires back apparently left them soldered in incorrect order; I am assuming that B+1 on the charger's board should be connected to battery's '+' and B-1 on the charger's board - to battery's '-'; but a helpful person nearby insisted on trying both possible configurations, just in case;
1.1. discharging capacitors (I am 90% sure which one is 'responsible') on the charger's board does resolve the problem (at least, temporarily; who knows when and why the capacitors may decide to get full again and the electrical circuit is no longer closed); 'problem resolved' is defined as 'blue light is on and battery charger provides electricity to USB port to charge a phone'; yes, the charger is double-function, as common, providing electricity to either battery and/or USB cable;
1.1.1. attempts to use human body as volt-ampere meter for a live (plugged-in) battery charger - yes, my fingers are sensitive to an electrical current passing through them, such as ordinary AA battery - left me with electrical shock (220V; predictable with my carelessness) and no apparent negative consequences (not even shaking hands);
1.2. the wires are broken again, this time at a different place; even more delicate soldering will be required, this time;
2. I have yet to order micro-USB port for N900, since they all look different, and I have no idea how to filter for those most similar (by shape?) to the original one;
2.1. shipping is usually awfully slow for online-bought items;
2.2. soldering micro-USB is a risky undertaking; I would like something most similar to default factory technique for attaching USB port; should it be soldering and/or epoxy? If soldering, then at what temperature? If epoxy, then what kind of epoxy? Considering the delicacy of surroundings, epoxy adhesive cured at room temperature would probably be preferable?

Best wishes.
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Per aspera ad astra...