How Long Does A 30000mAh Power Bank Last? | Runtime Math

If you picked up a 30,000 mAh pack, you want a clear answer on how long it keeps phones, tablets, cameras, and even laptops alive. Here’s the plain-English math, the real-world gotchas that shrink or stretch runtime, and quick tables you can use before a trip or an all-day shoot.

Quick Runtime Snapshot

The table below uses common device sizes and conservative loss assumptions. It gives you a fast estimate before we step through the details.

Device Type	Typical Battery (Wh)	Estimated Full Charges/Hours
Smartphone (4,500–5,500 mAh)	17–21 Wh	≈ 4–6 charges
Small Tablet (7,500–8,500 mAh)	28–32 Wh	≈ 2–3 charges
Large Tablet (10,000–12,000 mAh)	38–46 Wh	≈ 1.5–2 charges
Handheld Console	13–20 Wh	≈ 4–7 charges
Ultrabook Laptop	50–60 Wh	≈ 1 charge (light use)
Mirrorless Camera	9–16 Wh	≈ 6–10 charges
Action Cam	4–6 Wh	≈ 15–20 charges

What “30,000 mAh” Really Means

Manufacturers quote milliamp-hours at the pack’s internal cell voltage, usually around 3.6–3.7 volts. Energy is easier to compare in watt-hours (Wh). The conversion is straightforward:

Watt-hours (Wh) = (mAh ÷ 1000) × Volts

So for a 30,000 mAh pack at 3.7 V: (30,000 ÷ 1000) × 3.7 ≈ 111 Wh of stored energy. That’s the energy inside the cells, not the energy that reaches your phone or laptop. USB steps that 3.7 V up to 5 V (or to 9–20 V for USB-C PD), and every conversion wastes a slice of energy as heat. Good packs still lose some, and the device wastes a bit while charging as well.

30,000 mAh Power Bank Runtime — Real-World Factors

Two packs with the same label can deliver different results. These are the big swings that change how long a charge lasts.

Conversion Losses

Energy moves from 3.7 V cells to 5–20 V output, then into the device’s charger. Each step trims usable energy. Quality packs often land near 80–90% overall from cell to USB port under moderate loads. Lower-end designs can dip to the 70% range. Fast-charge at very high wattage also warms the electronics and drops efficiency.

Cable And Connector Quality

Thin or long cables waste power as heat. Poor connectors trigger voltage drop and slower charging. A certified USB-C cable rated for your target wattage keeps losses low and maintains stable PD negotiation.

Temperature

Cold cells deliver less; hot cells waste more. Room temperature yields the best balance. Leaving the pack in a hot car or charging under a pillow hurts runtime and ages the cells faster.

Battery Age

Every cycle shaves capacity. After a year of heavy use, 5–15% fade isn’t unusual. If your fresh pack delivered six phone charges last spring and now it’s closer to five, that’s normal wear.

Device Behavior While Charging

Streaming video on a tablet while charging means part of the pack’s output runs the device, not the battery. That stretches charging time and cuts the number of full refills you get from one portable pack.

The Math, Without The Headache

Use this simple approach for a decent ballpark:

1. Convert the pack to watt-hours at 3.7 V: 30,000 mAh ≈ 111 Wh.
2. Apply a realistic efficiency range to get usable energy: 111 Wh × 0.8–0.9 ≈ 89–100 Wh at the port.
3. Find your device battery in Wh. If you only know mAh, multiply by its battery voltage (phones/tablets often sit near 3.8 V nominal). Example: 5,000 mAh × 3.8 V ≈ 19 Wh.
4. Divide: 89–100 Wh ÷ 19 Wh ≈ 4.7–5.3 full phone charges.

Worked Examples

Modern Smartphone

Battery around 4,500–5,500 mAh at ~3.8 V is ~17–21 Wh. With 89–100 Wh usable from the pack, count on 4–6 refills, leaning closer to four if you’re gaming or tethering while charging.

Small Tablet

Many sit near 28–32 Wh. Expect about 2–3 refills, assuming you charge with the screen off and avoid heavy multitasking during the top-off.

Ultrabook Laptop

Many 13-inch models carry 50–60 Wh packs. With a 30,000 mAh bank, you can often refill once from 10–20% to near full, or run the laptop directly over USB-C PD at 30–45 W for a short flight. Demanding loads at 65–100 W can outrun a portable pack’s output budget and reduce overall energy delivered.

Mirrorless Camera And Action Cam

Mirrorless batteries often land in the 9–16 Wh range; action cam cells are much smaller. Topping camera batteries through a USB charger or a camera with USB-powered charging can net 6–10 mirrorless refills or a handful of action cam swaps for a weekend shoot.

Flight Rules You Should Know

Air travel has watt-hour limits for lithium-ion. The standard cap for carry-on is up to 100 Wh per battery; larger spares at 101–160 Wh need airline approval, and batteries go in cabin bags, not checked. A 30,000 mAh pack rated at 3.7 V is about 111 Wh, which sits over the 100 Wh baseline. Some big packs mark 27,000 mAh to stay just under the 100 Wh line. Check the label before you fly and ask your airline if you’re over the line.

For an official rule page, see the FAA lithium battery limits. If you need the watt-hour formula, the FAA also publishes the exact math: divide mAh by 1000 to get Ah, then multiply by volts to get Wh. A quick reference lives here: Wh calculation guidance. The TSA aligns on the same 100 Wh threshold for consumer cells and shows the allowances on its site as well.

Losses: Where The Energy Goes

Why does a large pack not translate one-for-one to device refills? Three places take their share:

• Voltage step-up: Cells sit near 3.7 V; USB output is 5–20 V. Boost converters waste a slice as heat.
• Device charging electronics: Phones, tablets, and laptops regulate incoming power and warm up under fast charge.
• Cables/connectors: Resistance turns a bit of power into heat, more so with thin or long cables.

What Changes The Outcome Most?

The table below ranks the big levers. Tweak these and you’ll see real differences in how long your pack lasts.

Factor	Typical Range	Effect On Runtime
Overall Efficiency	70–90%	Biggest swing; every 5% loss trims a phone charge
Charge Power	10–65 W	Higher wattage warms electronics; expect fewer refills
Device Use While Charging	Screen off → gaming	Using the device diverts power; refills drop fast
Cable Quality/Length	0.5–2 m, various gauges	Thin/long cables waste watts; slower, hotter, less total energy
Temperature	5–35 °C preferred	Cold reduces output; heat raises losses and ages cells
Cell Age	0–20% capacity fade	Older packs deliver fewer charges even with same label

Simple Rules Of Thumb

• Phones: Expect about five refills if you charge screen-off at night. Stream while charging and that number drops.
• Tablets: Two refills is a safe bet for 10-inch models.
• Laptops: One refill for thin-and-light models when the pack and laptop agree on USB-C PD profiles.
• Cameras: A weekend’s worth of swaps from one big pack, especially if you top off between shoots.

How To Stretch Runtime

• Charge at moderate power. PD at 18–30 W on phones is a sweet spot. Turbo modes raise heat and waste.
• Use short, certified cables. Keep one sturdy 60 W or 100 W USB-C cable for laptops and a short cable for phones.
• Top off early. Shallow charges waste less than recovering from 1% with max power draw.
• Keep it cool. Shade on the dash, never under a pillow, and avoid glovebox heat.
• Don’t drain to zero every time. Partial cycles are easier on lithium cells over the long run.

Buying Tips For Big Packs

Specs on the box tell part of the story. Look for these cues when choosing a large portable charger:

• Clear Wh marking. The label should show watt-hours, not only mAh. That helps with airline rules and honest comparisons.
• USB-C PD profiles you need. Phones do well with 20–30 W; many modern laptops need 45–65 W for steady charging.
• Real safety certifications. Listings such as UL/ETL matter. A protection suite (over-current, over-temp, short-circuit) should be stated clearly.
• Cycle life data. Makers that publish rated cycles signal better engineering and quality control.
• Cable in the box. A high-wattage USB-C cable saves guesswork and keeps losses down.

DIY Estimate You Can Reuse

Want a quick way to gauge any pack, not just the 30,000 mAh class? Use this repeatable method:

1. Find the pack’s Wh on the label. If only mAh is shown, convert with Wh = (mAh ÷ 1000) × 3.7.
2. Multiply by 0.85 for a realistic usable number. If your pack and cable are premium, 0.9 is reasonable; bargain gear may sit near 0.75.
3. Look up your device battery in Wh. If you only see mAh, convert using the device battery voltage (often ~3.8 V for phones/tablets).
4. Divide usable Wh by your device Wh for the rough number of full refills. If you plan to use the device while charging, trim that estimate by 10–25%.

Method And Assumptions

Calculations here treat 30,000 mAh at 3.7 V as 111 Wh of stored energy. Usable energy at the USB port assumes 80–90% conversion efficiency across boost electronics plus typical cable/device losses under moderate loads. Device battery sizes reflect mid-range values across current models. Charging while using the device is modeled as a direct draw that reduces effective refills.

Bottom Line On Runtime

A well-built 30,000 mAh pack gives most phones around five clean refills, small tablets two or three, and an ultrabook one full cycle. Real-world conditions push that up or down: charge slower, keep things cool, use solid cables, and you’ll get closer to the high end of those ranges. If you’re flying, confirm the Wh on the label and match it to airline policy before you head to the airport.