Chosen Solution
I’ve been trying to fix my iPhone but the battery dosen’t seem to be working. Checking the logic board battery connectors with the multimeter reads .55v but the battery reads nothing. Red and black is how I connected the multimeter leads.
There’s no polarity problem when measuring with a multimeter, what you’ve done is correct. Reversing probes polarity gives you the correct tension with a minus sign on display, that’s all. The battery connector reading you got points to a faulty charging circuit that requires microsoldering skills and tools to be fixed, not a DIY job.
