Why is the high current from the battery in a 3.7

O

Odessamarin2014-10-03 14:01:25

Electronics

Odessamarin, 2014-10-03 14:01:25

Why is the high current from the battery in a 3.7 - 5V DC converter dangerous?

Hello,
I want to use powerful lithium batteries to charge my phone, tablet...
I have an old battery from an electric bike. In it, cell li ion is standard 3.7V but with a high current ceiling of 20A. I bought this booster converter from 3.7 to 5B.
FX-608-PCBA DIY 1.2" LCD Dual-USB Output 5V Boost PCB Module w/ LED for Mobile Power - Silver + Blue
www.dx.com/p/fx-608-pcba-diy-1-2-lcd-dual -usb-outp...
But there, they say, the ceiling of the batteries should not exceed 4A. What will happen if you connect my version. Warm up more.. or something more serious? If anyone understands, tell me pliz.
Thank you!

Reply

Answer the question

In order to leave comments, you need to log in

4 answer(s)

A

Anton Kuzmichev, 2014-10-03
@Assargin

As far as I know, the current ceiling only means how much its maximum can be taken, but this never means what exactly 20A will be. Purely worldly: by connecting a phone to the 18650 element to charge, I will discharge this element in a few hours, but if I connect an LED, then it can burn for many days from such a battery - the LED consumes less.

G

gleb_kudr, 2014-10-03
@gleb_kudr

This means approximately that if you connect a load with a maximum consumption of more than 4A, then the battery will happily give it out and burn your converter.
If the power consumed by the end device is less, then less power will be taken from the battery (logically) and the converter will work normally.
To completely avoid problems, a current limiter can be built into the circuit.
In the case of charging a lithium battery, i.e. when the consumer is another battery, they can accept almost any current. And not only burn your converter, but also explode, for example. Therefore, a current limiter is an absolute must.

O

Odessamarin, 2014-10-03
@Odessamarin

Thanks, that's what I think too. But I was confused in the description (clumsy translation from Chinese into English ..)
that the battery protection should pass no more than 4 A.
"The maximum current of the battery with protection PCB cannot be over 4A"
"Using the battery with protective plate, self battery protective plate maximum current is higher than 4 a, 4A affects booster effects"
So I decided to ask again. Maybe these boosters do not like high current at the input, or they do not know how to limit it, i.e. take as much as needed)

Y

Yaroslav, 2014-10-08
Ohty @jar_ohty

It's just that in some tablets the implementation of battery charging is utterly simplified - the CC (current stabilization) mode is implemented simply by limiting the current by the source. Accordingly, when a powerful battery is connected, it will give out all the current that is possible and the battery in the tablet will catch fire or explode.