I recently bought a non-working boosted v1. At first, id get red lights indicating that the battery is low. But then I stopped getting any lights at all. I started taking it apart, I found 3 dead cells. I charged them back up to 3.3v and they’re holding charge. I noticed that the main terminals are not showing me a voltage. But when I test battery 1 and battery 12 then I get the voltage.
but there is voltage on the battery? Try testing between one leg, postive or negative and the opposite polarity on the battery, sounds like a broken phase wire, Not difficult to fix if it is.
IF you have a multimeter check for continuity between the battery active and the PCB active and likewise for the negative.