@ chowdit1: Short answer: back up your data, batteries fail. If your saves are important to you, have a copy on another media, whether it's flash or a floppy.
I'm not a GB user but the issue of saves is common to almost all embedded systems. I'm sure others can answer to the specifics of the GB,with ways to transfer saves from it. I know somewhere in one of these replies someone mentioned how they transferred their saves.
Yogi

So pretty much, like I just said?

FRAM is Ferromagnetic RAM (google it!), basically allows RAM to retain data even without a power source (like traditional RAM).

By the way, welcome fellow Alabamian. In Tuscaloosa, here.

Thanks.

matters the size of the sav file
the size of the sav file may matter

whatever.  haha

Usually they're always 32KB, for the data that most all GameBoy cartridges save. I think LSDJ saves a MUCH bigger size.

Getting a job usually helps your situation.

It's a joke.

By the way, welcome fellow Alabamian. In Tuscaloosa, here.

I've looked into the possibility of throwing FRAM into non-FRAM flashcarts. Still on the fence about whether or not to do it, but technically there are drop-in replacements for chips I have isolated in some of my cartridges. Just want to let you know that option also exists though it has mostly gone unrealized.

What does FRAM do?

Generally, RAM chips hold their data down to around 2V, but check your data sheet for specifics.
I would suggest that you approach the charging problem with a automatic circuit, charging the battery when the cart is docked. Dallas Semi, and I'm sure others did also, used to make a RAM supervisor chip to control switching from mains to batt.
There is never going to be a 100% fail-safe design; the batts will drain if the cart is left in a box for years, or the batts will fail over time with reg use. Battery backed RAM is not a permanent media, could be why we don't see too many RAM based devcarts.
For truly 'safe' you need to back it up. A batt will buy you some time, but only diamonds are forever.There are some newer chips out that operate as RAM and save to Flash on power fail, but speed and density may be an issue ATM.

So you're saying to put a game that uses a battery save, into a flash cart, and then backup the save onto whoever's computer, to keep from the battery dying, and losing the save.

that sort of thing

its not really a straight multiplier like you'd think (32x8), its telling you how the data is grouped.  just written that way to identify its architecture, so to say

well, the FM18W08 has 8x32k, so 256k shouldnt be a problem, unless the gameboy cart only can address one of the banks. if thats the case, well have to look for a 1x128k or more.

I think you are confusing bits and Bytes. Without researching this chip in particular, the common convention is to list the bit size of a device - 256Kbit or 256Kb, this can also expressed as 8x32K. as in a 32KByte, 32KB device. This can be very confusing, but manufactures use the bit size because some devices can be used in  8bit or 16bit data bus systems. I think Kitsch mentioned the pitfall of this mistake ( I feel your pain Kitsch, have done the same!!).