Firstly, the conclusion is given: according to the national standard GB/T 35590, the conversion rate is ≥80% when it is not clear; Generally, **5V/2A≥80% and 9V/2A≥75% are regarded as qualified lines in the industry, and below 60%**, the virtual standard can be basically judged. Let's make it clear from three aspects: standard, self-test and actual measurement.
First, look at the official qualification line (GB/T 35590-2017)
Definition: Conversion rate η = (output energy ÷ rated energy of battery) ×100%
Mandatory requirements:
Marked by the manufacturer: not less than the stated value.
Unmarked: ≥ 80% (23 2℃, standard load)
Common gear threshold (CCC certification reference):
5V/2A：≥80%
9V/2A：≥75%
12V/1.5A：≥70%
Second, simple self-test (without professional equipment)
1. Look at the "rated capacity" (mandatory labeling after 2024)
Battery capacity (such as 20000mAh)÷ rated capacity (such as 12000mAh)≈ conversion rate.
Example: 20000mAh battery, rated at 12000mAh → 12000÷20000=60% (lower limit of qualification); Rated 16000mAh→80% (standard line)
2. Reverse the charging times (the most practical)
Formula: charging times ≈ (nominal capacity× conversion rate) ÷ cell phone battery capacity.
Example: 20000mAh power supply →iPhone 15(3349mAh)
80% conversion rate: 20000×0.8÷3349≈4.8 times.
60% conversion rate: ≈3.6 times
Conclusion: iPhone 15 can be charged for less than 3 times with 20000mAh → the conversion rate is less than 60%, which is a false standard.
3. Rough weight judgment (auxiliary)
10000mAh：180–230g； 20000mAh：350–420g； 30000mAh：＞500g
The same capacity is too light → poor batteries and low conversion rate.
Third, professional measurement (accurate judgment)
1. prerequisites
Environment: 23 2℃, let stand for 0.5–1 hour after full charge.
Load: standard constant current loads such as 5V/2A and 9V/2A.
Equipment: power meter, electronic load and data recorder.
2. Calculation steps
Measure the rated energy of the battery cell E = nominal capacity (Wh)
After full charge, discharge with standard load to cut off, and record the output energy E.
η=（E₁÷E₀）×100%
3. Grading reference (industry group standard)
Grade 1: ≥88% (excellent)
Grade 2: 86%–88% (good)
Grade 3: 80%–86% (qualified)
< 80%: unqualified; < 60%: seriously false standard.
Fourth, the main points of avoiding pits
Just looking at "battery capacity" is a trap, and we must look at the rated capacity and the measured conversion rate.
Low price and large capacity (such as 20000 mAh < 50 yuan), light weight, overheating → high probability of conversion rate < 60%.
Give priority to products with 3C certification, rated capacity and actual measurement report.
