Making a 2P battery out of old phone batteries.

Using Arduino General Electronics
#1

Hi!
I'm definitely kinda new at this, so I was wondering if some of you could lend some help.
I'm trying to make a battery capable of supporting 2A being drawn out of it, I have some old phones lying around and the batteries are working fine, they charge and discharge, no problem there.

The Batteries are 1Amph and 1.5Amph, I'm guessing both are 1C so they can give out 1Amp and 1.5Amps respectively, so together in a parallel configuration they should give 2.5Amps, or 2Amps, I'm fine with any of those really.

So I've been looking around at how to charge batteries, and you just need to make the cells go to 4.2V which is the voltage they have when they're fully charged.
I also got some 18650s lying around so I bought these:

That can easily connect to the phone adapter and charge with a phone cable, I tested it on an 18650 and It works just fine, what it does is it simply stops allowing current once it sees that the battery has 4.2V

So, how would I do it if I wanted to charge a 2P battery?
Like, I'm thinking that this dude couldn't see the Voltage of a single battery to see who it should keep charging and who he should stop charging, like one battery were to be 2.4 and the were to be 3.8.

Also the adapter I gave you in the link can only output 1A of current, but I need 2Amps (max. draw from sim800L module), I don't really know how to search for these things as I don't know how they are called, so if you guys could search for one like the one in the link but which can output 2A(If that's even possible) I'd appreaciate it!, it'd be even better if you could educate me and tell me how these things are called or how they work! I'm always interested in learning new things! :smiley:

These are the two phone batteries I want to join in case you are interested:
LG: LGIP-580N
SAMSUNG: gb/t18287-2000

#2

It is not a good idea to mix old batteries, especially if they are of different capacities, as the setup is impossible to charge properly.

#3

jremington:
It is not a good idea to mix old batteries, especially if they are of different capacities, as the setup is impossible to charge properly.

Actually, if we are referring to series connections, which is what is usually implied, you require a “balance” charger which charges both separately, so a slight difference in capacity should not matter.

The danger is in discharge as one will discharge before the other and be damaged unless its protective circuit copes with the situation (by disconnecting it entirely).

Whilst paralleling them is not optimal, they should generally both charge and discharge safely - given again a proper protective circuit for the pair.

#4

sergih123:
So I've been looking around at how to charge batteries, and you just need to make the cells go to 4.2V which is the voltage they have when they're fully charged.

You need to look a bit more. That's not how you charge lithium-based batteries. They're charged using a CC/CV method...first you charge them at a constant safe current until they reach 4.2V. Then you hold the voltage constant while the current reduces until they are full.

Steve

#5

if we are referring to series connections,

"We" are not. The OP specified 2P.

#6