Chapter 82

"Hey, cat girl, what are you doing!"

"Master Joshua, is it okay?"

I called out for Ellie, but it was Alru who came. She immediately grabbed Sequoia from behind and dragged her along. However, when Sequoia protested, Alru stopped dead in her tracks. Then, she tilted her head cutely and asked me what she should do. I nodded and waved my hand.

"Goodnight, Sequoia. See you tomorrow."

"Ugh, just wait and see!"

"I'll deal with you when I calm down a bit. Talking about science and magic with you never ends, and I can't sleep if I don't."

"There's no choice, but it feels embarrassing to be dragged along like this."

Sequoia, who was dragged all the way to the door, said this. Alru stopped and looked at her with a carefree smile.

"Would you like a piggyback ride, Sequoia?"

"I'll walk on my own."

Sequoia quickly broke free from Alru and started walking. Alru bowed and the door closed with a soft thud.

"Phew."

I lay down on the bed and let out a big sigh. I haven't even taken a bath yet, but it's no problem to skip it for a day. I haven't changed clothes either, but once I lie down, I can't get up. I've been relying on everyone, not just Sequoia, but also the penguins and Torre at the forge. I feel really bad about it. I was absent for the battery project the other day.

---

Three days ago, at the forge.

I was looking at a house when I got a call from Penguin, so I hurried to the forge. Penguin, using his flippers, was holding a rectangular glass container about a meter long and wobbling as he walked. It looked precarious.

"Where are you moving it to?"

"Come to think of it, there's no need to move it. It's a defective product, you see."

"Huh? Isn't that a battery, like a small aquarium?"

"It's a prototype. I made it with the materials you provided."

"Wow. It's a bit larger than the batteries I know, but is that a problem?"

"No, that's not a problem. This is a lead-acid battery, one of the most widely used and oldest types of storage batteries. It's a defective product, though."

Wow, Penguin.

You said you could make a lead-acid battery if you had the materials, and you really did. But you said it's a defective product. Why?

I tilted my head, and Penguin started explaining the reason for the failure.

"It's a durability issue. Since it's not optimized, the liquid capacity is too large. There's a risk of the glass breaking."

"When you lift it, the weight of the water is uneven, right?"

"Exactly. The outer frame needs to be reinforced with iron or something."

"I see. So, it needs a bit more work. If we reinforce the outside with iron, it won't be easy to mass-produce, right?"

"I think it depends on the use. No, wait. We're too stuck in our ways."

"Oh, right! Indeed."

Habits can be scary.

Penguin and I were both stuck in the same mindset. When we hear 'battery,' we think of something portable. Even car batteries are fixed in the car but are still portable.

So, we had the idea that batteries are portable.

However, what we're trying to do is convert electricity into mana. We just need to create a pool of electricity, and there's no need to move it. If we need portable batteries later, we can reinforce them with iron or something.

Just as Penguin and I were high-fiving, Sequoia, who had been watching us, interjected.

"Did you manage to make the battery?"

"Yeah, it just needs to be charged."

"Why don't we try it right away!"

Sequoia's eyes sparkled, and I wholeheartedly agreed. However, Penguin made an unexpected comment.

"Joshua, have you made the converter? I don't see anything like it."

"Oh..."

I completely forgot! The improved water wheel generator is now stable, and I was so satisfied with that.

"The electricity generated by the water wheel is alternating current."

"What's a converter?"

Sequoia, who was excited by the unfamiliar word, immediately asked.

"A converter... it's a rectifier. The electricity generated by the water wheel can't be used to charge the battery as it is."

"Hmm, interesting. From the name 'rectifier,' I guess it straightens out the electricity?"

"Exactly! The electricity generated by the water wheel is created by rotating a magnet, so the direction and amount of the current are not constant."

"So, it straightens it out, right?"

"Right. I completely forgot..."

When you generate electricity by rotating a coil or magnet, you get alternating current. Since the current is not constant, you need to make it constant—i.e., direct current—to charge the battery. That's the role of the rectifier... the converter.

But how do you make it? In modern Japan, I could easily make a converter, but this world doesn't have the materials for a converter.

"Have you not made the converter yet? Let's prepare it quickly."

Penguin said this nonchalantly, ignoring my groans.

"But, to make a converter, you need semiconductors..."

That's right. You can easily make a converter with semiconductors. Semiconductors are small, inexpensive components. But making semiconductors is beyond my capabilities. I'm not sure if Penguin can do it. My understanding is that making semiconductors requires precise mechanical engineering.

However, Penguin gave me an unexpected hint.

"Look at the wonderful technology we have here. The beautiful light bulb."

"Right! Vacuum tubes!"

Exactly!

A diode can be made using a vacuum tube. I had forgotten that this world has the "vacuum magic" technology, which is amazing. With vacuum magic, you can remove only the air from a sealed container. As long as the seal is tight, creating a vacuum is easy.

"But, Penguin, do you know how to make a vacuum tube?"

"No problem. You should know the basics, right? Since you made the light bulb."

"Vacuum the glass container like a test tube and attach electrodes... something like that?"

"Pretty much. With Torre and Garam's skills, it should be quick. We can use Sequoia's magic to create a vacuum."

"Oh, oh!"

I got so excited that I ended up jumping around with Sequoia. The fusion of magic and science is amazing.

---

So, I asked Penguin about the vacuum tubes. Even for something as simple as a battery, I rely on everyone. I never thought I could do everything on my own. The construction and operation of the town are only possible with everyone's cooperation. I'm just the one waving the flag. But, it's a lot of work! I'm so sleepy...

I'm sorry, everyone. Thank you.

As I thought of my gratitude, sleepiness quickly overcame me.

Yawn, good...

I plan to eventually change the converter to a diode.

Diode = vacuum tube, note to self.