Power bank charging time is typically 3–12 hours, shaped by capacity, charger wattage, and USB-C tech.
Looking to figure out how long a portable battery takes to refill? The answer hinges on a few simple numbers: the energy inside the pack, the input power from your wall charger, and how the electronics manage heat and efficiency. This guide gives you plain math, quick lookups, and clear tips so you can set expectations and pick the right charger for faster refills.
What Decides Charging Hours
Three variables set the pace:
- Capacity (energy to fill) — Usually listed in mAh; what you need for timing is watt-hours (Wh). The rough relation is Wh ≈ (mAh × nominal cell voltage) ÷ 1000. Most packs use cells around 3.6–3.7V.
- Charger input power (W) — Your wall brick’s maximum output, plus the protocol the power bank accepts (plain 5V, USB PD, Quick Charge, etc.).
- Real-world overhead — Conversion, heat limits, and the taper near 100% add time. A simple way to plan is to assume you get about 80–90% of the wall-plug watts as effective charging power into the pack.
The Handy Formula
Use this quick estimate:
Hours ≈ (Energy in Wh) ÷ (Charger watts × 0.85)
That 0.85 factor stands in for losses and charge taper. It’s not exact, but it lands close enough for planning.
Fast Reality Check
Before diving into details, here’s a snapshot you can use straight away.
Capacity Vs. Charger Power: Estimated Hours
| Pack Size (mAh) | Charger Power | Estimated Hours |
|---|---|---|
| 5,000 (≈18.5Wh) | 10W | ~2.2h |
| 5,000 (≈18.5Wh) | 18W | ~1.2h |
| 5,000 (≈18.5Wh) | 30W | ~0.7h |
| 10,000 (≈37Wh) | 10W | ~4.3h |
| 10,000 (≈37Wh) | 18W | ~2.4h |
| 10,000 (≈37Wh) | 30W | ~1.4h |
| 20,000 (≈74Wh) | 10W | ~8.6h |
| 20,000 (≈74Wh) | 18W | ~4.9h |
| 20,000 (≈74Wh) | 30W | ~2.9h |
| 26,800 (≈99Wh) | 18W | ~6.4h |
| 26,800 (≈99Wh) | 30W | ~3.9h |
| 26,800 (≈99Wh) | 45W | ~2.9h |
| 30,000 (≈111Wh) | 18W | ~7.2h |
| 30,000 (≈111Wh) | 30W | ~4.3h |
| 30,000 (≈111Wh) | 65W | ~2.0h |
These entries assume nominal 3.7V cells and an 85% wall-to-pack efficiency. Your unit’s display or app may show slightly different times because of pack design and thermal limits.
Power Bank Charging Hours Guide — Typical Ranges
Here are practical ranges that match common gear on shelves today:
- 5,000–10,000mAh: ~2–6 hours with 10–18W input; ~1–3 hours with 30W input.
- 20,000mAh class: ~5–9 hours with a 10–18W brick; ~3–5 hours with 30W input; faster with 45–65W if the pack accepts it.
- 26,800–30,000mAh: ~6–10 hours on 18W; ~3–5 hours on 30–45W; ~2–3 hours on 65W+ capable designs.
The bottleneck isn’t always the wall charger. Many models cap their input (e.g., 18W in, even if you plug into a 65W brick). Check the spec sheet for an “Input” line and the protocol (USB PD, PPS, Quick Charge). If the pack lists only 5V/2A, expect a slower refill.
How To Convert mAh To Wh For Timing
Most listings show capacity in milliamp-hours. To time charging, convert to watt-hours first:
Wh = (mAh × nominal cell voltage) ÷ 1000
Nominal cell voltage is commonly 3.6–3.7V. A 10,000mAh pack at 3.7V is about 37Wh; a 20,000mAh pack is about 74Wh. Aviation pages also show this relation since airlines rate limits in Wh; see the FAA’s guidance for the Wh formula.
Fast Chargers, USB-C, And Why Cables Matter
With USB-C and Power Delivery, some packs now accept much higher input power than old 5V bricks. The USB-IF outlines PD 3.1 profiles that reach far above 100W on capable cables and devices. That’s output capacity, yet it signals what the ecosystem can handle; plenty of power banks use a slice of that headroom for swifter input. Read more at the USB-IF’s page on USB Power Delivery.
The cable is part of the story. USB-C to USB-C leads come in different power ratings. Many are labeled for 60W or 240W. Using a cable that can pass the needed current helps a high-input pack reach its advertised speed.
Worked Examples You Can Copy
10,000mAh Pack With An 18W Brick
Energy ≈ 10,000 × 3.7 ÷ 1000 = 37Wh. Effective input ≈ 18 × 0.85 = 15.3W. Time ≈ 37 ÷ 15.3 ≈ 2.4 hours.
20,000mAh Pack With A 30W USB-C PD Charger
Energy ≈ 20,000 × 3.7 ÷ 1000 = 74Wh. Effective input ≈ 30 × 0.85 = 25.5W. Time ≈ 74 ÷ 25.5 ≈ 2.9 hours.
30,000mAh Pack That Caps At 18W Input
Energy ≈ 30,000 × 3.7 ÷ 1000 = 111Wh. Effective input ≈ 18 × 0.85 = 15.3W. Time ≈ 111 ÷ 15.3 ≈ 7.3 hours.
Why Your Timer Still Drifts A Bit
Even with tidy math, a few pack-level behaviors nudge the clock:
- Taper near full: The last 10–20% often slows to limit stress and heat. Many brands show a quick rise to 80%, then a gentle finish.
- Thermal throttling: A hot desk or pouch can force the input to drop. Cooler ambient air helps maintain the rated input.
- Electronics overhead: DC-DC conversion and cell balancing shave watts along the way, which is why the 0.85 factor keeps estimates grounded.
Picking The Right Charger For Your Pack
Match two things: the protocol and the wattage. If your power bank lists “USB-C PD input up to 30W,” then a 30W PD charger (and a capable cable) is a sweet spot. Going far above that won’t push more power unless the pack is built to ask for it. If your unit’s input is 5V/2A, a basic 10W adapter is all it can sip, no matter how large your wall brick is.
Quick Pairings That Work Well
- 5,000–10,000mAh: 18–30W PD charger.
- 20,000mAh class: 30–45W PD charger, PPS if the pack lists it.
- 26,800–30,000mAh: 45–65W PD charger when the spec sheet says the input allows it.
Fast Ways To Shorten The Wait
These tweaks shave real time without new gear:
- Ventilation: Set the pack on a hard surface so heat escapes.
- Single-task the port: Many models slow input if they’re also charging a phone. Unplug the phone until the pack finishes.
- Use the shortest capable cable: Less resistance helps keep input near the negotiated target.
When The Label Doesn’t Match Reality
Marketing pages sometimes mix output figures with input figures. Look for the “Input” line. If it lists “USB-C: 5V⎓3A, 9V⎓2A,” that’s 15–18W max input. If it lists “USB-C PD: up to 45W,” your charger and cable need to match that to see the gain.
Charging Time Variables And Quick Checks
| Variable | What Changes | Practical Check |
|---|---|---|
| Input Ceiling | Caps the maximum watts the pack can accept. | Find “Input” on the spec label or manual. |
| Charger Output | Sets the headroom available at the wall. | Match PD/PPS profile and watts to the pack. |
| Cable Rating | Limits current; some leads top out early. | Use a 60W or 240W-rated USB-C to USB-C. |
| Thermals | High temps slow the charge curve. | Give the pack airflow; avoid soft bedding. |
| Pack Design | Cell count and management add overhead. | Expect a slow final stretch near 100%. |
Frequently Seen Specs, Decoded
“PD 30W In / 30W Out”
The model can both accept and deliver up to 30W using USB-C Power Delivery. If you pair it with a 30W PD charger and a capable cable, the refill time drops compared with a 10W brick.
“PPS” On The Label
Programmable Power Supply is a USB-C PD extension that lets devices ask for fine-grained voltage/current. Some power banks with PPS take in power more efficiently across the curve, which can trim minutes in the mid-charge range.
“Max 18W Input” Next To A Big Capacity
Large energy does not guarantee fast input. This spec tells you the pack won’t charge faster than 18W even if you use a beefy wall brick. Use the lookup table to set a realistic window.
Capacity Labels And Airline Limits
Many packs show capacity in mAh because it’s familiar. Airlines and travel rules use Wh since it maps directly to energy. The FAA explains how to calculate Wh from volts and amp-hours and uses that for limits and exemptions; see the FAA battery page linked above. If your label shows only mAh, you can still convert it using the same relation used for flight checks.
Set Your Expectations In One Minute
- Find energy in Wh: Multiply the mAh by 3.7 and divide by 1000.
- Check the input spec: Note the max watts and the protocol on the power bank.
- Match a charger: Use a wall brick and cable that meet or beat that input.
- Do the math: Divide Wh by (charger watts × 0.85). That’s your ballpark hours.
The Bottom Line For Faster Refills
Speed comes from the pairing. A power bank with a higher input ceiling, a PD charger that meets it, and a cable rated for the current will shave hours off the wait. Keep the pack cool, avoid charging a phone from it while it’s refilling, and you’ll get closer to the times in the table near the top.
Notes On Assumptions
This guide uses 3.7V as the common nominal cell voltage and an 85% factor to reflect real-world overhead and taper. Many cells are highly efficient during charge at the chemistry level, yet the whole system has switching losses, thermal limits, and a final slow approach near full. That’s why your app or LED bar may show a fast climb early and a relaxed finish.
Extra Reading If You’re Curious
Want the big-picture view of USB-C and PD? The USB-IF page on USB Power Delivery outlines the range of supported power levels. For energy math used in travel rules, the FAA’s battery guidance lays out the Wh formula you can apply to any label.