Rated vs cell capacity
Usable output vs the printed cell rating.
Why it matters
Real output ≈ 60–70% of the label. A 10,000 mAh bank gives roughly 6,500 mAh.
What to check
Good brands print 'rated capacity' on the back — compare that.
Electronics
Power Bank
A 20,000 mAh power bank does not give 20,000 mAh to your phone. Voltage conversion eats a third of it, and the output wattage decides whether it charges your laptop at all.
Quick answer
Rated capacity is ~60% of cell capacity.
20W+ PD for phones; 45W+ for laptops.
Check if max watts are shared or per port.
30W+ input for faster refilling of large banks.
In the shop
Ask the salesperson this exact question
Read these off your phone at the counter. The answer tells you more than the price tag.
1.“What is the real usable output after conversion loss?”
A good answer: Roughly 60–70% of the printed mAh. A 10,000 mAh bank gives about 6,500 mAh to your phone.
2.“What is the maximum output wattage and does it support my phone's fast charging?”
A good answer: A watt figure plus the protocol name (PD, VOOC, etc.), not just “fast charging supported”.
Find your fit
A few questions about your situation, not about the product.
0/20
Add one short need not covered above.
Answer all 2 questions to see the spec sheet to shop with.
Extended warranty & AMC — what to check before you say yes
For electronics the expensive failures are the display, the board and the battery. Extended cover is worth it only when it names those parts and offers a repair path in your city.
Ask these five questions
- ✓Is the display / motherboard covered, and up to what value?
- ✓Is accidental and liquid damage included, or is that a separate add-on?
- ✓Is repair done at an authorised service centre with genuine parts?
- ✓Is battery degradation covered, and below what health threshold?
- ✓What's the turnaround promise, and is a standby device provided?
Usually not covered
- ×Theft and loss (that's a separate insurance product)
- ×Software issues, data loss and unauthorised repairs
- ×Batteries and chargers on most plans
- ×Cracked screens unless accidental damage is bought explicitly
Rule of thumb: worth considering on a high-value device you carry around, rarely worth it on a low-cost one where a plan costs more than ~15% of the price.
These are comparison links, not recommendations — we don't sell plans and we don't rank providers. Some outbound links on KnowBeforeBuy are affiliate links. Cover, exclusions and pricing change; read the plan document before you pay.
Check resale value of your old device
If you are upgrading, a buyback quote changes the real cost of the new purchase.
Get a quote onCashify
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Buy it locally
Shops near you that stock power bank
Sometimes the local dealer beats online on price, installation or the exchange offer. Tell us where you are and we'll list nearby stores. We don't rank or take money from any shop; results come from Google Maps.
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The spec sheet, decoded
Output wattage & protocol
PD (Power Delivery), QC (Quick Charge) and watts.
Why it matters
Phones want 18–30W PD; laptops need 45–65W PD. Mismatched protocol means slow charging.
What to check
'22.5W max' is often shared across ports, not per port.
Input charging speed
How fast the bank itself refills.
Why it matters
A 20,000 mAh bank with 10W input takes 8+ hours to recharge.
What to check
Look for 30W+ input on large banks.
Ports & pass-through
USB-C, USB-A count, and charging while being charged.
Why it matters
USB-C in/out is essential now; pass-through is handy overnight.
What to check
Some banks only charge via micro-USB — outdated.
Cell type & safety
Li-ion vs Li-polymer, plus protection circuitry.
Why it matters
Li-polymer is safer and slimmer; BIS certification matters for flights and safety.
What to check
Airlines restrict banks above 100 (~27,000 mAh).
Weight
Grams you'll actually carry.
Why it matters
20,000 mAh banks weigh ~400 g — heavy for daily pocket carry.
What to check
Match size to whether it's for travel or daily bag.
Before you pay
- ✓Decide daily carry (10,000 mAh) vs travel (20,000 mAh).
- ✓Check output watts per port and PD support for your device.
- ✓Confirm USB-C input at 30W+ on big banks.
- ✓Look for BIS certification and printed rated capacity.
Common traps
- !Ultra-cheap 20,000 mAh banks with fake capacity and no protection.
- !Buying a 65W bank for a phone that only takes 18W.
- !Banks too large to carry on flights.
10,000 mAh pocket banks to 20,000 mAh 65W laptop-capable units.