To choose the right charger for the right device increases the rate of charging, increases the lifespan of the device and decreases the risk of burn. There is always a risk of burn, but it can be minimized by many methods.
- Ohm's law
V = R I
where V
voltage, R
resistance, and I
current. Choose a cable which has more/same charge capacity (I
) than the phone.
General Summary
Exercises where try to answer the question marks
V (V) / V (V) /
I (A) I (A)
Cable Phone Decision
------- --------- --------
5V 1A 5V 2A No, burn risk
5V 2A 5V 2A Yes
5V 2.1A 5V 2A Yes
5V 2.4A 5V 2A Yes
5V 0.7A 5V 2.1A No, burn risk
5V 0.7A 5V 0.85A No, burn risk
5.2V 2A 5V 2A ?
5.1V 2A 5V 2A ?
4.9V 2A 5V 2A ?
4.8V 2A 5V 2A ?
5V 1A 3.8V 1.3A No
5V 3A 3.8V 1.3A Yes
9V 3A 3.8V 1.3A ?
9V 3A 5V 2A ?
5V 3A 5V 2.1A Yes (Edza case)
- burn risk - drawing more current from the cable which it supports is always a burn risk
- feel the charger with your hand; if it is very hot, reject; overheating will happen; since most chargers do not have protections besides the covering, the seller cannot recommend combinations with burn risk
[new table here where device has Snapdragon 810 or 820, since the situation will be little different in dynamic configurations]
Practical table where try to answer the question marks
For most USB chargeable smartphones the battery voltage is irrelevant. The USB charging circuit is often set to 5 V 0.5 A
V (V) / V (V) /
I (A) I (A)
Cable Phone Decision
--------------- --------- ----------
USB1 (5V, 0.5A) 5V 2A ?
USB2 (5V, 0.5A) 5V 2A ?
USB3 (0.9A) 5V 2A ?
USB-C 5V 2A ?
Apple's iPad
5V 2.1A 5V 2A Yes
Amazon's
Kindle fire
5V 1.8A 5V 2A No, burn risk
Car charger
5V 1A 5V 2A No, burn risk
Car charger
5V 2.1A 5V 2A Yes
Sources
Phones in examples: Oneplus 2, ...
Tools to study volt and ampere which your phone is charging: Ampere