When it comes to choosing the right battery, one size definitely doesn’t fit all. Whether you’re powering a fishing boat, a high-drain flashlight, or just replacing the button cell in your remote, choosing the correct battery is essential. In this guide, we’ll walk you through the essentials of three of the most searched battery types today: the Deka battery, the 21700 battery, and the 3 volt battery. You’ll learn what each one is for, where they perform best, and what to look for before buying.
Let’s take a closer look at how these three battery types compare and which one is the right fit for your needs.
What Is a Deka Battery?
If you’ve ever dealt with batteries for boats, RVs, or even solar systems, you’ve probably heard the name Deka thrown around. It’s one of those brands that comes up a lot — and for good reason. These batteries are built tough and made in the U.S. by East Penn Manufacturing, and they’ve got a solid reputation for lasting power and dependable performance in the field.
So what makes Deka batteries a solid pick?
For starters, they really shine in deep-cycle setups — great if you’ve got a camper van or an off-grid cabin running on solar. They’re also powerful enough to crank over big marine engines or work vehicles, which is why a lot of people who rely on their equipment every day stick with Deka.
One thing that sets them apart from your average lead-acid battery is their use of AGM tech — that’s Absorbed Glass Mat. Without getting too technical, it basically means the battery is sealed up tight (no spills) and doesn’t need maintenance. It also handles vibration way better, which comes in handy if you’re bouncing around rough terrain or choppy water.
You’ll see a few models pop up a lot:
There’s the Deka Intimidator — a favorite for RV and boat setups since it can handle both starting and deep-cycle duties. Then there’s the Dominator, which is a gel battery built to last through tons of charge cycles. And for cold weather starts, the Deka Gold has strong cold-cranking power that makes it a go-to for trucks and cars.
Bottom line? These batteries are built to take a beating and keep going. If you’re setting up power for a mobile rig or want something you don’t have to worry about for years, Deka’s a smart bet.
Switching gears — have you heard of the 21700 battery?
It’s been getting a lot of attention lately, especially among people using electric tools, e-bikes, or high-performance flashlights. The name “21700” just refers to its size — 21 millimeters wide, 70 millimeters long — but what’s inside is where the magic happens.
Compared to older 18650 batteries, the 21700 packs in more energy without adding much bulk. Most of them hold between 4,000 and 5,000 milliamp hours (mAh), which is a fancy way of saying they run longer before needing a recharge. That’s a big deal if you’re on the job or out riding and don’t want to constantly swap batteries.
Why people like ’em?
They’re efficient, hold a charge well, and tend to stay cooler even under pressure — which makes them safer for high-drain devices. You’ll find them in a lot of newer tech: high-end flashlights, power tools, even vape mods and scooters. They’re slowly becoming the standard for anything that needs steady, powerful, rechargeable energy.
Top 21700 Battery Brands & Models:
Samsung 40T – 4000mAh with a high discharge rate
Molicel P42A – 4200mAh, excellent for tools and vapes
Sony VTC6A – Trusted for consistent performance in flashlights
Because it’s rechargeable and has a longer cycle life, a 21700 battery is both economical and eco-friendly for long-term use. Be sure to check the compatibility of your device — not all flashlights or mods fit 21700 cells, especially older models.
Top 21700 Battery Comparison Table
| Model | Capacity | Max Discharge | Best For |
|---|---|---|---|
| Samsung 40T | 4000mAh | 35A | E-bikes, vapes |
| Molicel P42A | 4200mAh | 45A | Tools, mods |
| Sony VTC6A | 4100mAh | 35A | High-drain electronics |
Understanding 3 Volt Batteries
Funny enough, I didn’t think much about 3 volt batteries until my kitchen scale died and I had to hunt one down. Turns out, they’re in just about everything — car remotes, wristwatches, fitness bands, you name it. They’re small, simple, and surprisingly dependable.
Most of these batteries come in two styles: flat coin-shaped ones or short barrel-style cylinders. The CR2032 is probably the most common — you’ll find it in everything from bathroom scales to bike computers. Then there’s the CR123A, which looks more like a mini version of a regular battery and is usually found in flashlights or motion sensors.
Here’s a quick rundown of a few types you’ll come across:
CR2032: Reliable and easy to find. It’s the go-to for watches, medical gear, and small remotes.
CR2025: Same general idea, just a bit thinner — perfect when space is tight.
CR123A: Built for more power-demanding stuff like tactical lights and wireless alarms.
What’s nice is these batteries tend to last a long time — even if they sit in a drawer for years. I always keep a couple of Energizers or Panasonics around, just in case. When something stops working out of the blue, swapping in one of these can save you a ton of hassle.
When replacing a 3 volt battery, be sure to check both the voltage and model number. Though many look alike, even a small variation in size or chemistry can impact performance or device compatibility.
Battery Comparison Guide
Deka Battery
Use Cases: RV, car, marine
Size: Group 24–31
Rechargeable: ❌ No
Notable Models: Intimidator AGM, Gold
21700 Battery
Use Cases: Flashlights, e-bikes, vapes
Size: 21x70mm
Rechargeable: ✅ Yes
Notable Models: Samsung 40T, Molicel P42A
3 Volt Battery
Use Cases: Remotes, watches, toys
Size: Coin/Cylindrical
Rechargeable: ❌ Mostly not
Notable Models: CR2032, CR123A
Which Battery Should I Use?
Still unsure which type of battery to go with? Here’s a quick breakdown:
Choose a Deka battery if you’re running a high-power system in your RV, boat, or off-grid setup. They’re built for durability and long-term energy delivery.
Opt for a 21700 battery if you’re using high-drain electronics that need rechargeable lithium power, like e-bikes, mods, or tactical gear.
A 3 volt battery is your best bet for compact devices like remotes, fitness bands, and small electronics — easy to replace and cost-effective.
When you’re shopping for any battery, always check the manufacturer’s specs, voltage requirements, and size compatibility. Choosing the wrong one can lead to device failure or short battery life — both of which are easy to avoid with a little planning.
Frequently Asked Questions
Is a Deka battery good for solar backup?
Yes. Many Deka deep-cycle AGM batteries are ideal for solar energy systems and perform well in cyclic charging conditions.
Can I use a 21700 battery in place of an 18650?
Only if your device supports it. The 21700 battery is longer and wider, so check your product manual or battery compartment.
How long does a 3 volt battery last?
Depending on the device, a 3 volt battery like the CR2032 can last 2–5 years in normal usage. Shelf life can reach 10 years.
What’s the advantage of a 21700 battery over other lithium-ion cells?
More capacity in the same form factor, better energy retention, and typically longer cycle life.
Where to Buy
Shop the best Deka battery models for marine or RV use
⚡ Explore top-rated 21700 battery options for flashlights and mods
🔋 Find the right 3 volt battery for your remote, scale, or watch
Be sure to buy from reputable vendors to avoid counterfeits — especially for lithium batteries.
