Battery Pack
 

So im getting an avionics upgrade and my tech mentioned I have 4C Batteries that are corroded...Here is picture

Attachment 2777

What is it for and what does it actually do?

I understand it has to do with something with the alternator jump start???

Yep, that's the restart pack. The pilot is supposed to test the system every 25 hours. I don't suspect that has happened.

Would this cause my "Rear ALT" warning light to constantly wink, and the occasional constant on? I just bought this plane in May, so I am learning, and I have never had to deal with an alternator restart button.

Sometimes when I turn on all the lights to put on a load, the alt light goes out.

Im just confused, on what I need to do or check to make sure this battery pack is properly working.

That really needs cleaned up, and make sure the ground side is still connected. The batteries are used for alternator restart in the event they get knocked offline. The restart procedure is in your POH and spelled out in the maintenance manual.

Your alternator out light is more of a function of the board assembly that is on the front of the firewall by your regulators. On this board are two big diodes behind it and on the front are smaller diodes, resistors, and two rectangular reed relays. This whole board assembly is what turns off and on your alternator out lights.
Much info is available on other threads.

Search is your friend. The answer to all of your questions (at least most) may be found in other threads on the board.

Your restart system is likely fine, but that battery tray needs to come out and be scrubbed with water and baking soda until all the corrosion is gone.

Battery acid is nasty stuff and can be very destructive, so add "C" batteries to the list of things to check at annual, and test the system every 25 hours as mentioned.

The blinking alternator lights are a symptom of a poor electrical system design. Search for "Electrical System Upgrade" and you should find some threads discussing the upgrade kit I supply that eliminates the blinking lights and allows your alternators to truly work in tandem with one another. Price is $599 shipped.

Thanks for the info, I was told the tray was beyond cleaning...its going to get replaced.