Storing new marine batteries

[PNjunction]

... i picked up a G7200 on sale and lo and behold it says "lithium" on the box, nothing about gen2, but i guess that's what it is
it's in my trunk, now i just need to sneak it past the mrs....

Yep, that's a Gen2! Sneak it past the mrs before you run return-by date passes, and test it on your car. Like all consumer goods these days, it is wise to check. My first Gen2 7200 had to be returned as it was brain-dead. (despite having a good fuse in the clamp leads, and verified connectivity with the quick-disconnects.) Note, if that fuse IS blown, or the connection is super poor, then you won't be able to do anything but activate the power supply until the issue is fixed.)

re: first let the charger do it's normal thing...

START off with a normal charge (14.4v setting), for those fla's or if sub freezing, then cold/agm.

Here's the best part - the Gen2's seem to be a tad smarter about float - while I haven't witnessed sitting at 13.6v automatically, I DID notice that it didn't seem to just shut off like the earlier Gen1 versions did, and will do a float by offering the battery some current and allowing it to set the pace when absorb is finished (aka their "optimization" stage) - which in my case was just hovering at about 13.2v - similar to a battery tender's float. If there was a *significant* parasitic draw, then it would restart the maintenance cycle again, either that or just discharging down to the target low voltage. Of course they don't specify what level that parasitic current trigger actually is!

It drives me nuts how charger manufacturers try to spice things up with their funky descriptions that don't go into FULL detail. So there does appear to be a limited type of automatic float without you having to do anything like you would with the Gen1's. BUT, that doesn't stop you from doing so if you like!

The Gen1's specifically mentioned that the "13.6v supply" mode can be used to float large batteries, but this detail is missing in the Gen2's. Perhaps that limited type of float, hidden among the "optimization" cycle is the reason they don't mention it any more.

All the rest you mentioned sounds pretty good, except with FLA's instead of topping them off with a manually selected 13.6v "supply", perhaps it would be simpler to just let them sit on the Gen2's seemingly limited float, OR just start another normal charge cycle letting it do its thing automatically and wait another 30 days while it "optimizes"/mini-floats things in between. ha.

The gen2 simplifies things somewhat, although that means testing it within the return period to make sure it works!

You've got kind of a swiss army knife of chargers now. If those batteries do go funky, you've got the "repair" mode (similar to an EQ you do on floodies, but limited to 4 hours), manual supply/float, and now even an AGM+ mode for those batteries that can take it. In fact, I'm doing a quick test with the agm+ mode on an optima right now! I'll let you all know how that goes.

[Sunking]

1) bring home 2 new 80ah marine FLA batteries

2) charge them INDIVIDUALLY by doing this to each one:

Why? Put them both in Parallel and let them charge 24 hours.

If all you are going to do is charge them, no reason to charge them separately. If you have the means, there is no reason to ever disconnect them and just let them Float on the charger all winter. You will not have to do anything all winter except relax. Next spring they will be fully charged and ready to go.

[PNjunction]

The reason I recommend charging brand new batteries individually before putting them in parallel is out of an overabundance of caution in case one of the batteries has an unforeseen problem. One of which may be a large difference in battery voltages if you don't check with a voltmeter first. That can lead to a problem / spark at least, and if one of them has a bad cell ....

A smart charger will be more easily able to detect a bad/weak cell letting you identify the culprit easier if charged individually, and also help ensure that the cells get off to a good start.

In addition, only the end-cells are truly paralleled with each other, and the inner cells by necessity aren't.

Doing it individually just helps you vet that the each battery is acting like normal under charge upon receipt, and there is less chance for a weak / runt cell to hide - at least initially for the very first charge. If all goes well, then parallel and treat like one thereafter, although now charge/discharge on the diagonals of course.

Watching with a temp-compensated hydrometer is of course the best plan of action, but for the simplistic slapping of two batteries together with nothing more than a simple charger, then I'd do it individually at least once at the start.