Important!
This was that Macintosh SE article that I’ve found that has a second monitor connected to the Macintosh. This appears not to tell of the battery specifications.
20170930/DuckDuckGo macintosh se wisdom teeth removed
20170930/http://www.obsoletecomputermuseum.org/mac_se/
What should we use for the replacement battery on the Macintosh SE? This. “3.6V Lithium 1/2 AA PRAM Battery for Mac.” Actually, this is pretty easy to buy from Batteries Plus+. Just look for a lithium 1/2 AA. Make sure you specifically ask for a lithium battery as you do not want the battery to leak inside of your vintage computer equipment.
The batteries used in the Macintosh computers listed in the specs tab are lithium, and are 3.6V.
20170930/DuckDuckGo macintosh se pram battery
20170930/http://www.newertech.com/products/pram_3_6v.php
Beware, however, that the early Macintosh SE just solders the battery directly into the board. The later models like SE/30 and SE FDHD use a socket to make the battery easily removable. The recommendation?
you can solder in place a battery socket for a “1/2 AA”; the same type of PRAM battery used by the SE/30 and like Mac models sharing that battery.
Don’t worry if you can’t replace the battery, though. The early Macintosh SE will still boot without one.
20170930/https://68kmla.org/forums/index.php?/topic/16627-macintosh-se-pram-battery/
Well, if I am going to need to put a battery socket in, I might as well also take the opportunity to locate the battery off the mainboard, right? What is the best way to build the battery compartment so as to prevent leaks from damaging the vintage electronics?
Failed search.
20170930/DuckDuckGo how should you build a battery compartment to contain leaks
Okay, so now I’m going to have to make this call myself. Plastic is a tough material, it should be able to hold up well against leaked battery chemicals. That being said, the box that contains the battery should be made out of some sort of plastic and mostly close up, but the closure shouldn’t be gas-tight, as batteries can release gas.