After unplugging the usbc power, blue leds continue to all blink , every 10-20 seconds or so for about two minutes.. What is this telling me?

From my experience something is wrong with the battery I connected the battery reversed to see what it would do and the LEDs started blinking like you described

Is this what i need to convert a device that takes 2 AA batteries over to using an internal lithium battery? Does this have overcharging protection?

Not quite. Yes it will charge a lithium battery safely, with a 4.2v float voltage (works with standard 3.7v nominal lithium ion or lithium poly cells) but the output is boosted to 5v for the load side. 2xAA devices usually want 3v. You could pair this with a 3v LDO module to drop the output to the voltage you need, though, but really you want a plain charger (no boost) and a 3v LDO as this will be more efficient

ASIN	B09YD5C9QC
Best Sellers Rank	#114,140 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #426 in Power Converters
Customer Reviews	4.2 4.2 out of 5 stars (98)
Date First Available	April 12, 2022
Item Weight	1.76 ounces
Item model number	B09YD5C9QC
Manufacturer	DWEII
Package Dimensions	5.31 x 3.58 x 1.38 inches

DWEII 10PCS Type-C USB 5V 2A Boost Converter Step-Up Power Module Lithium Battery Charging Protection Board LED Display USB for DIY Charger ( no Welding Version)

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