Why My S24 Plus Charged Faster Than My S25 Plus in Mumbai’s September Heat: A Full Real-World Test

Why the Galaxy S24 Plus Charges Faster Than the S25 Plus in Mumbai’s September Heat

I didn’t set out to turn this into a long investigation. It started as a simple moment on a sticky September evening in Mumbai. I plugged in my S25 Plus at 20 percent and expected it to climb quickly, the same way my S24 Plus always did. But when I checked 15 minutes later, the progress bar seemed slower than usual.

That small doubt led me to do tests across two days, at different times, with the same charger and cable, inside my home where the weather feels heavier than outdoors. By the end of those tests, I had a clear answer: the S24 Plus stayed cooler, and because of that, it charged faster.

Most tech outlets don’t test phones in Indian humidity. They test in air-conditioned offices. They look at wattage numbers and battery sizes and move on. But fast charging behaves differently in a real home, in real heat, with real weather pressing down on your walls.

Here is the clearest explanation I can give, based entirely on hands-on testing inside Mumbai’s late monsoon climate.

Quick Answer

The S24 Plus charged faster because it stayed cooler during fast charging. The S25 Plus heated up quicker in Mumbai’s humid September weather, triggering Samsung’s temperature-based safety limit. Once the battery crossed about 40°C, the S25 Plus slowed the wattage to protect the battery, making it charge slower than the S24 Plus.

Why This Test Matters

Fast charging is advertised in clean numbers: 45 watts, 65 watts, 120 watts. But wattage is not the real story. Temperature is.

You can have the most powerful charger in your hand, but if the battery hits a limit, the phone will protect itself. Indian homes without AC, especially in Mumbai’s humid months, push phones close to those limits.

I wanted to see how both phones behaved under the same conditions because this is how most people will charge their devices: after work, at home, in a room that’s warm, not cooled.

And the difference surprised me.

Where the Test Happened: My Actual Charging Environment

I live in Mumbai, where September evenings have a heavy, lingering warmth. My testing room is a small bedroom with no AC and minimal ventilation. I usually keep the windows open, but the humidity still sits thick in the air.

Real conditions during testing:

• Temperature: 31°C to 33°C
• Humidity: 70 to 82 percent (based on local weather app)
• Surface used: Wooden table
• Fan speed: Medium
• No case on either phone

These details matter because humidity slows down heat dissipation. When air is already thick with moisture, devices cool more slowly. This isn’t something brands mention, but you see it instantly when you watch the battery temperature rise during charging.

The Testing Setup (Controlled and Simple)

I wanted both phones to have identical conditions, so I kept things strict:

• Charger: Samsung 45W PD charger (original)
• Cable: 5A E-marked fast-charging cable
• Phone mode: Flight mode on both devices
• Starting battery: Exactly 20 percent for each test
• Same table, same outlet, same fan position
• Both phones cooled to room temperature before start

I repeated the test three times to make sure the results weren’t random.
Charging Results (Three Test Sessions)

Session 1 - Evening (Around 7:45 PM)

• S24 Plus: 20% → 80% in 28 minutes
• S25 Plus: 20% → 80% in 36 minutes

Session 2 - Afternoon (Around 3:30 PM)

This was the hottest session.

• S24 Plus: 20% → 80% in ~29 minutes
• S25 Plus: 20% → 80% in ~38 minutes

Session 3 - Night (Around 11:15 PM)

Coolest session of the three.

• S24 Plus: 20% → 80% in ~27 minutes
• S25 Plus: 20% → 80% in ~34 minutes

The S25 Plus was consistently slower.

Temperature Observations (Most Important Part)

I used Samsung’s built-in Device Care > Battery diagnostics to monitor battery temperature during the full session.

S24 Plus

• Start: 32°C
• Peak: 38–39°C
• Charging curve remained stable
• No sharp thermal spikes

S25 Plus

• Start: 32°C
• Hit 40°C within the first 8–10 minutes
• Peak around 41–42°C during the hottest test
• Charging wattage drop triggered instantly

Once the S25 Plus crossed 40°C, the wattage visibly dipped. You can feel it in the charging behavior: the early fast ramp slows down, then settles into a controlled drip.

Samsung prioritizes battery safety here, not speed.

Why the S25 Plus Heated Up Faster: The Real Reasons

This is the section tech sites skip because they don’t test in humidity or intense heat. But once you observe the temperature spikes, the pattern becomes clearer.

1. The S25 Plus pushes high wattage earlier

Samsung seems to have tuned the S25 Plus to reach its peak wattage faster in the early stage of charging. This is usually good, but in humid places, the battery warms up too quickly.

The phone then corrects itself by cutting charging speed.

In short:

More power too early → more heat → reduced wattage → slower overall charge.

2. Slimmer frame = less room to spread heat

Phone bodies are getting thinner. That extra bit of thinness removes some breathing room for heat to disperse. What you lose is thermal buffer. This matters most in places like Mumbai.

The S24 Plus feels slightly better at spreading heat across the back panel. The S25 Plus heats up in a more concentrated patch.

3. Mumbai’s humidity is a silent factor

Heat is one thing.
Humidity is another.

Mumbai’s late monsoon months trap heat inside walls, bedsheets, cushions, everything. Devices stay warm even before you start charging them.

If the battery begins at 32°C instead of 28°C, you are already closer to the safety limit.

Humidity slows cooling by:

• reducing airflow efficiency
• keeping device surfaces warm
• maintaining heat longer than dry air

This is not theory. You can feel it when holding the phone warmth lingers.

4. Safety rules are tighter on newer models

Brands have become more cautious about battery management after years of global pressure. The S25 line follows stricter software rules that reduce charging speed earlier to prevent overheating.

This is a protective feature, not a flaw.

Why the S24 Plus Stayed Cooler (Based on Real Use)

The S24 Plus seems to manage heat better, at least in warm climates. The back panel feels cooler to the touch even 15 minutes into charging.

Here’s what I think contributes:

• More stable wattage ramp

It pushes power more steadily instead of aggressively.

• Slightly better heat spreading

It distributes heat across the panel instead of forming a hotspot.

• More forgiving thermal limits

It seems to tolerate small temperature spikes better.

• Less aggressive fast-charging software

It waits longer before throttling.

This doesn’t make it superior overall, but in hot weather, small differences matter a lot.

My Experience Watching Both Phones Charge Side-by-Side

I sat with both phones during the third session at night. It gave me the clearest picture.

First 10 minutes:

S25 Plus temperature shot up quickly.

S24 Plus rose slowly.

At 15 minutes:

S24 Plus was still cool enough to push strong power.

S25 Plus was already throttling.

At 25 minutes

S24 Plus was comfortably past 60 percent.

S25 Plus was struggling to stay within limits.

Touch difference:

When I placed my palm on the back panel, the S25 Plus felt warmer even though the room was cooler at night.

These observations only appear in real-world tests, not in lab-controlled results.

What This Means for Users in Hot Indian Cities

It doesn’t matter which phone you own. Heat decides your charging speed more than the brand or model.

If your room is hot:

• fast charging drops
• thermal controls kick in
• wattage falls
• charging takes longer

The S25 Plus is not “bad.” It’s just more sensitive to heat than the S24 Plus.

How to Keep Charging Fast in Indian Weather

These steps genuinely helped during my testing:

1. Charge in the coolest corner of your room

Away from windows and walls that hold heat.

2. Remove the case

Even thin cases trap heat.

3. Use original chargers + 5A E-marked cable

Cheaper cables heat up more.

4. Don’t charge immediately after gaming or camera use

The battery is already warm.

5. Keep the phone on a hard surface

Beds and pillows trap heat under the device.

6. Use a fan

Even a slow fan reduces surface temperature.

These won’t break Samsung’s safety system, but they help prevent early throttling.

Is Something Wrong With the S25 Plus?

No. The phone is behaving exactly how its software is designed to behave. The battery is being protected, which is a good thing for long-term health.

Heat is the reason behind the slower charging, not a defect.

In cooler months, you’ll likely see little to no difference between both devices.

A Deeper Look at Battery Temperature Limits (What Tech Sites Don’t Explain)

Fast charging is only “fast” inside a safe thermal window.

Most phones try to stay under:

• 40°C during early charge
• 42°C during mid charge
• Crossing these numbers, especially in humid climates, forces throttling.

Samsung devices are known for being strict with limits, which is why the S25 Plus slows down quickly once the room gets warm.

Your S24 Plus simply stays below that line for a longer time.

Author Michael B Norris observation

1. A charging behavior pattern most people miss

One thing I noticed while repeating the tests is that the S25 Plus does not recover its fast-charging speed once it throttles, even if the room cools slightly mid-session. The S24 Plus sometimes does.

On two runs, when the fan lowered surface warmth after the first 15 minutes, the S24 Plus briefly increased charging pace again. The S25 Plus never did. Once it slowed, it stayed slow until around 70 percent.

This tells me Samsung’s newer thermal logic favors consistency over recovery, even when conditions improve.

2. The back panel heat “shape” difference

Heat didn’t just feel higher on the S25 Plus. It felt more localized.

On the S24 Plus, warmth spreads wider across the back, especially toward the upper half. On the S25 Plus, the heat forms a tighter hotspot near the center, right where the battery sits.

That concentrated warmth makes the phone feel hotter faster, even when total temperature numbers are close.

3. A small timing detail that explains the slower result

During all three tests, the S25 Plus lost the charging race in the first 12 minutes, not the last 20.

After throttling, both phones charged at similar slower speeds. The final difference came from the early phase where the S25 Plus overheated and gave up its advantage too soon.

In other words, the S25 Plus didn’t charge slower overall. It failed to hold fast charging long enough.

Why This Article Is Different From Typical Tech Content

Big outlets test phones in studios with AC. They run charging tests on desks with constant airflow. They publish numbers that don’t match what Indian users experience in their bedrooms or living rooms.

I test phones how most people actually use them:

• in hot rooms
• with humidity
• on real surfaces
• after long days
• during late monsoon nights
• with the same chargers people already own

These conditions reveal behaviors that spec sheets never show.

Final Thoughts

Both phones are excellent. But when the weather turns warm and humid, the S24 Plus holds its speed better because it stays cooler during the early charging phase.

The S25 Plus has stricter thermal protections, a slimmer body, and a more aggressive early wattage push all of which cause temperature spikes that lead to slower charging.

In short:

The heat, not the hardware, made the S25 Plus charge slower.

If you live in a hot city like Mumbai, expect your fast charging to vary depending on the room temperature, the season, and even the time of day.

Visit Samsung official website for more latest information 

Author: Michael B. Norris 

Michael B. Norris is an independent tech analyst focused on real-world smartphone performance in Indian conditions. He tests devices in non-AC homes, high heat, and humidity to study charging, battery health, and thermal behavior based on first-hand daily use, not lab simulations.

Site: TrendingAlone 

TrendingAlone is an independent tech review site created to test smartphones the way people actually use them. Reviews are based on hands-on testing, controlled comparisons, and long-term use in Indian climate conditions, prioritizing accuracy, transparency, and user trust over specs or hype