Minn Kota Battery Charger Problem

I recently upgraded to lithium batteries for my trolling motor, with that I had to upgraded my charger to accommodate said lithium batteries. I talked to the manufacturer and they recommended I use a Minn Kota 330PCL. So I purchased one off of Marketplace and installed it. This is where the problems start, I bought an AGM starting battery to obviously start the boat and run my electronics. After a little over a year the AGM battery was garbage and they would not warranty it due to miss charging… I went to batteries plus and bought another AGM this time an X2 100ah. After 6 months the battery would no longer charge, I brought it back and it took batteries plus 2 days to bring it back to life and they say “its good to go”…

So my question is has anyone ever had this happen where a charger destroys batteries? Is there a way to test and make sure the charger is working properly or did i get a dud? Or do I just have that much bad luck?

If by Marketplace you mean Facebook, and bought it used, I would first assume the seller knew it was bad and scammed you. Are you sure you set the battery profile to AGM for the AGM battery? In the charger manual it gives the different charge curves and voltages. You could try putting a voltage tester on the charger leads when first plugging in and check to see if it matches up with the volts for that charge curve.
How long have the PCL chargers been out, there is a two year warranty.

Yes, I did get it off of Facebook Marketplace, it was “new in box” but in today’s world I guess I need to take that with a grain of salt. I will pull the manual out and double check the curves and voltages line up with what they should be.

I’m not sure how long the PCL chargers have been out, I’m going to try and find a manufactured date and see if it is within two years. With my luck it’s at 25 months

I read the full instruction book first. Less rejects that way.

After charging a AGM battery and letting it rest for a couple hrs, your voltage reading on a good battery should be in the neighborhood of 12.8 volts. You need to wait a couple hrs or overnight before doing this. If you are 12.6ish battery is bad

You need to set all batteries individually. Read the instructions on how to do that. Set the agm to the agm setting and the other 2 on lithium. While you can charge a lithium on the agm setting, you don’t want to charge the agm on the lithium or flooded settings.

All of the batteries are set correctly.