Can I split a 9 V battery into two 4.5 V batteries for two LEDs?

A 9V alkaline battery will have six 1.5 V cells. These are like short AAAA cells. If you can find a tube the right size, put 3 cells end to end to get two 4.5V batteries. There are some single LED penlights now that use AAAA cells. Perhaps adjust the length (copper spacer), and a 9V is easier to find than an AAAA.

There is a link to a site below where you can get penlights.

A 9 V carbon-zinc usually has six rectangular Sandwiches held together with a shrink wrap tube that also maintains contact pressure.

A 9 V round battery has 6 round sandwich cells.

I don't think I've seen these in alkaline. These are about 2x the capacity of the rectangular, or about 1 Ah.

An easier way would be to wire the two LEDs in series. As you wire more devices in series, the drain on the battery is the same, but the voltage is split between the devices.

----- a caution ---

different color LEDs have different forward voltage drops

IR perhaps 1.5 V

visible ~2V-3V

UV perhaps 4.5V

this voltage is quantum physics and the PN junction

white LEDs are florescent lamps ( UV LEDs exciting RGB phosphors )

the cheapie 9 LED flashlight usually parallels the 4.4V UV LEDs

with 3 AAA cells in series and no dropping resistor.

+++

I wonder if it's possible to insert internal wiring into the battery to turn it into a pair of 4.5V batteries in parallel? TBH I'd rather investigate using 3 AAAA (or other size) cells in an appropriate holder from the start than try dismantling batteries. I think it would be more reliable.

---

never parallel cells

they must be identical or the weaker one will be charged by the stronger

a+b< 2a+2b/2

if you have room use AA instead of AAA

cells in series work pretty well but for some reason the + cell seems to drain first