FDOT ran a program a while back providing free replacements of the old battery powered SunPass transponders
with new units with no battery. Unfortunately they sent me a dud (in the sense that the serial number cannot be registered) with the only recourse being for me to buy a new one for $25.
I pried the useless brick apart to see what’s inside.
The unit is very difficult to open but is not weatherproof. This should be noted by anyone planning to use one on a motorcycle.
Here’s the board inside. Not much to it. What are the extra pins? No circuit traces are attached to them. The two between the two that are in use are not even soldered down. It’s reasonably possible that only two of the ic pins are used – this is not uncommon at all on passive RFID devices. Antenna, antenna ground.