I understand, getting a replacement battery locally is a problem, and the cost of getting a battery from overseas is very high.
Trying to use a powerbank instead brings up many potential issues: voltage differences, charging differences, possible over-current situations, and another cable to be dealt with coming from the cam. Hardly worth trying as cheap as cam batteries are.
Phil
I agree with SawMaster: I would not consider a PB as a replacement for the dashcam's integrated battery. If your decision does come down to a choice between using a PB or paying a lot of money to get a replacement dashcam battery from overseas, I would rather entertain getting a new dashcam instead (clearly a third choice yet). If you get a new dashcam, it can be a newer model, as opposed getting the same dashcam you currently have. So, in the process, you will (likely) get access to newer dashcam features, and newer technology, plus will also have a new dashcam as well, with everything that a new dashcam would entail, such as a new warranty. The warranty on your current (bad battery) dashcam is likely no longer good. From your dashcam battery having gone dead, I would guess your dashcam is perhaps several years old and that explains why the dashcam battery will no longer hold a charge. So, do you really want to continue investing in old technology when the cost of both a new PB and the (shipping) cost of the replacement battery would both be too high, maybe as high as the cost of some new dashcams? Also, how do you know for sure the problem is with the battery? You wouldn't know that for sure until you replace the battery, which you obviously have not yet done. If you don't know this for certain, then your getting a replacement dashcam battery could turn out to be an exercise in futility: you do all that work (soldering, etc.) just to discover something other than the battery had gone bad with the dashcam, or perhaps --worse yet-- something went bad
in addition to the battery. Yes, trying to run off a PB may seem like a brilliant idea on the surface, but it can create unexpected problems and, in fact, you could end up damaging the dashcam beyond repair. As a way of comparison, when the battery in a cell phone goes bad, what do most people do? Do they try to run the cell phone of a PB? No, some people might go to a shop (alluded to by one of the participants above) and get the battery replaced, but most people I know simply get a new cell phone altogether. Hope this helps.