0. A 2007 anime can turn into a technology time capsule without warning
Rewatch an older show and sometimes the biggest shock is not the plot. It is an ordinary object in the background.
The mobile phone is a perfect example.
“Lucky Star” was adapted into an anime in 2007.[1] Hearing people from that era talk about a phone battery lasting roughly two years can sound startling today.
Two years? That is it?
A modern smartphone may stay in service for three or four years, so “two years” sounds like the whole device is expected to die.
That is the trap.
For many Japanese phones of that period, the battery was a removable consumable. “Two years” was much closer to replace the battery pack and keep using the handset than to throw the phone away after two years.
And if we compare time between charges rather than battery aging, old feature phones could look almost ridiculous.
1. “Two years” did not mean the same thing as a dead sealed smartphone
Many Japanese phones in the 2000s had a rear cover and a user-removable battery.
A tired battery could be handled like this:
open cover → remove pack → insert new pack → respawn
Today, a degraded smartphone battery often means a manufacturer repair or authorized service visit. Battery replacement has become a repair event instead of a small part swap.
NTT Docomo’s old service model makes the difference especially clear. Its Premier Club offered a free battery pack to eligible users who had kept the same FOMA handset for at least two years. From December 2007, users in the one-to-two-year window could also exchange 500 points for a battery pack.[2]
So the period’s logic was not “your phone dies after two years.”
It was closer to:
“After a couple of years, refresh the consumable battery and continue.”
That makes the same number feel very different.
2. Between charges, old feature phones could be monsters
The 2006 FOMA N902iX HIGH-SPEED listed about 560 hours of stationary standby time.[3]
That is roughly 23 days.
No, that does not mean 23 days of calls, mail, gaming and constant screen use. Standby figures were measured under specific conditions and are not equivalent to normal daily use.
Still, the number is striking.
The FOMA N901iC listed about 430 hours of stationary standby and about 350 hours while moving.[4]
Modern smartphones, meanwhile, illuminate large displays, run powerful processors, stream video, use location services, operate several radios, process photos, receive notifications and synchronize apps in the background.
A 2000s feature phone was mainly a phone and messaging device with extras.
A modern smartphone is closer to a pocket computer that still happens to include a phone app.
Comparing standby days as though the workloads were equivalent misses the point.
3. Battery technology did not stop improving; the phone simply collected too many jobs
This is the funny part.
Modern batteries, power management and chips have improved enormously. Yet many people still charge every day.
Why?
The workload expanded fast enough to eat the gains.
Screens became larger, brighter, sharper and faster. Networks became faster. Cameras became miniature computational-imaging systems. Phones added constant location awareness, Bluetooth, background synchronization, local machine-learning workloads and far more demanding applications.
At the same time, users still expect the device to remain thin.
It is like increasing a game character’s maximum mana and then unlocking twenty new spells that are all permanently equipped. The mana pool improved. The character just became much more expensive to run.
The battery did not become stupid.
The phone learned too many tricks.
4. The battery itself is generally more cycle-durable now
Charging every day does not automatically mean modern batteries wear out faster.
Apple says batteries in iPhone 14 and earlier models are designed, under ideal conditions, to retain 80% of original capacity after 500 complete charge cycles. For iPhone 15 and later, the design target is 80% after 1,000 cycles.[5]
A charge cycle is not “one time you plugged in the cable.” It is the cumulative use of 100% of battery capacity.
The EU has also applied ecodesign requirements since June 2025 that, for covered smartphones and tablets, include at least 800 charge-discharge cycles while retaining at least 80% of initial capacity.[6]
So two different metrics must be separated:
- old feature phones could sit idle for a very long time between charges;
- modern smartphone batteries are engineered to survive large numbers of cumulative cycles.
Runtime per charge and service life of the battery itself are not the same thing.
5. The cost comparison reveals the biggest cultural shift
Old battery packs were cheap enough to feel like accessories.
For several Docomo models around 2004–2005, official battery-pack prices were ¥1,470 or ¥2,205.[4][7]
The user could replace the pack without paying for device disassembly.
Modern smartphones are different.
Samsung Japan’s repair table updated on September 9, 2026 lists, for example, battery replacement from ¥7,469 for the Galaxy S23 Ultra, ¥11,550 for the Galaxy S25 and ¥15,070 for the Galaxy S26 Ultra.[8]
Apple currently provides model-specific battery-service estimates, with the final amount depending on inspection, coverage and service conditions.[9]
These numbers are not a clean inflation-adjusted comparison. The old figures were battery-pack prices, while modern figures often include professional repair labor.
But the structural change is obvious:
| Comparison | 2000s feature phone | Modern smartphone |
|---|---|---|
| Battery | Often user-removable | Usually internal |
| Replacement | Swap the pack | Often a repair procedure |
| Price examples | ¥1,470–¥2,205 | Roughly ¥7,000–¥15,000+ in current examples |
| Downtime | Potentially immediate | May involve shop or shipping |
| Coverage | Free-pack programs existed | Warranty/coverage plan changes the price |
Old phones could respawn from battery aging with almost insulting ease.
6. So why not simply make every battery removable again?
That sounds reasonable, but the trade-off is not one-dimensional.
Modern phones are designed around thin bodies, large batteries, water and dust resistance, structural rigidity, cameras and dense internal packaging. A removable battery does not make water resistance impossible, but a frequently opened cover, contacts and locking hardware add design constraints.
The sealed design gained packaging freedom.
It also lost repair convenience.
That is why the more useful modern question is not simply “removable or sealed?” It is:
How serviceable can a sealed device be?
The EU’s current rules address not only battery endurance but also disassembly, repair and spare-parts availability.[6]
We may not return completely to “pop the back, drop in a new pack,” but repairability has become a product characteristic again.
7. Conclusion: batteries did not regress; the amount of work we feed them exploded
A phone from the “Lucky Star” era produces a strange reversal when viewed from 2026.
A two-year battery-replacement rhythm sounds short.
But standby times could reach hundreds of hours. Replacement packs could cost only a few thousand yen. Some users could even receive a replacement pack free under carrier programs.
Today we may charge almost every day.
But the battery is designed around hundreds or a thousand full cycles, while the device performs workloads that a 2007 handset could not remotely attempt.
So the twenty-year story can be compressed into one sentence:
Battery technology improved, and smartphones immediately spent the improvement on becoming dramatically more capable.
The real time capsule is not the capacity number.
It is the maintenance ritual.
Then:
“Battery is getting weak. I’ll buy another pack.”
Now:
“Do I book a repair, check coverage, or just replace the phone?”
You start by watching an anime.
You end up studying two decades of mobile-device maintenance design.
Sources
- https://group.kadokawa.co.jp/sustainability/project/animetourism.html group.kadokawa.co.jp
- https://www.docomo.ne.jp/info/news_release/page/080418_01.html docomo.ne.jp
- https://www.docomo.ne.jp/info/news_release/page/20060824a.html docomo.ne.jp
- https://www.docomo.ne.jp/info/news_release/page/20050125a.html docomo.ne.jp
- https://support.apple.com/ja-jp/101575 support.apple.com
- https://energy-efficient-products.ec.europa.eu/product-list/smartphones-and-tablets_en energy-efficient-products.ec.europa.eu
- https://www.docomo.ne.jp/info/news_release/page/20040617.html docomo.ne.jp
- https://www.samsung.com/jp/support/mobile-devices/please-tell-us-about-the-repair-cost-of-the-galaxy-device/ samsung.com
- https://support.apple.com/ja-jp/iphone/repair/battery-replacement support.apple.com
