Been a while, but I did see a "battery hack" done on Youtube. The video creator takes apart a 9 volt transistor battery which reveals four quad A (AAAA) batteries. Those are then used to power AAA cell device.
My findings: Eveready carbon zinc cell. The internal batteries are rectangular, and stacked like coins in a bank's coil roll.
Rayovac, carbon zinc cell. The internal batteries are rectangular, and stacked like coins in a bank's coil roll.
Duracell, alkaline. Sure enough, contains six eaches quad A batteries. Spot welded together. Oh, well. But, didn't the hack guy..... yes! That's it!
Energizer. The battery the hack guy used. I pulled one apart (diagonal cutting pliers work much better than needle nose). Sure enough, six loose quad A cells, with the necessary contacts and spacers. Tried them on my battery tester and find all of them dead. How can that be? Some of them lit a bulb? Turns out the polarity is reversed. The center stud end is negative, the flat closed end is positive.
Now, for the practical trying out. I get a Harbor Freight short light, using three eaches AAA cells. Unscrew the cap, and slide out the sabot.
No joy.... the batteries are too short to reach the contacts. Turns out, not worth the bother. Unless one is an engineer and can make sleeves to make the AAAA cells longer.
I had (past tense) a Streamlight, pocket light that took two eaches AAAA cells. Left the batteries in, and they corroded. Couldn't get the batteries out, later. Sigh. Another useless hack.