Charge laptop battery with Variable Power Supply

Thread Starter

eduaqa

Joined Dec 14, 2020
6
I'm wondering how to charge a notebook battery (DELL) using my CV/CC power supply .
Battery has 9 pins
P+,P+
P-,P-
P-,C,D (I believe for SMBus communication)
SYS , I believe means "system present", because I have to connect to the ground to have output on P+,P-
ALE, I believe for thermstor

I though that just grounding the SYS, and connecting the power supply to P+,P- would be enough, but was not, I put power suppler in 12.9V/1300mAh (each cell of battery individually should be changer at 4.3v), but there not current flowing, the drain from power supply is 0A.
What am I doing wrong?
 

Dodgydave

Joined Jun 22, 2012
9,848
There will be a circuit board inside the battery case , for battery protection and charging, so unless you can control it then you will have to remove it and replace it with a different one.
 

Thread Starter

eduaqa

Joined Dec 14, 2020
6
Correct, I was wondering how to control it, maybe the motherboard do some SMBus "coding" "saying start charge" "stop", etc
The strange part is that the internal circuit when a ground the SYS pin "turn on" the P+,P-, but just in one direction, so I can drain the battery, but, not charge
 

Ian0

Joined Aug 7, 2020
1,120
A friend tried this with his model aircraft battery. He needed a new conservatory, and as it was a uPVC convervatory that burned down, there was a large amount of smoke damage in the rest of his house.
 

Thread Starter

eduaqa

Joined Dec 14, 2020
6
Yes, I agree they are dangerous, and only should be done if you read the specs and follow then, for sure you need a CC/CV and follow the specs, maximum A, maximum V, stop load when reach specific A drain.
If you overload the A, or the V not following the specs and don't cut when reach the specific drain you will be in trouble.
 

Audioguru again

Joined Oct 21, 2019
2,374
I use two old 18650 lithium-ion cells in a portable little vacuum cleaner to replace its old Ni-CAD battery. I charge it overnight with an LM317 voltage regulator set to 9.1V in series with a 1N4001 diode for a voltage of 8.4V (4.2V per cell). No fire (yet).
 

Thread Starter

eduaqa

Joined Dec 14, 2020
6
Yes, I also use them after disable the computer battery pack following the specs without problem. But now what I'm trying to do is charge the pack without disabling, and as was said there is internally on the pack a circuit the has 9 pins and control everything which is not allowing me to do it.
 

Thread Starter

eduaqa

Joined Dec 14, 2020
6
Just as a tip when loading in series for example, the Samsung 18650 says load on 4.3v ... you should not just do 4.3v + 4,3v and inject 8.6v, because one battery can be in different condition than the other and one receive for example 4.5v and other 4.1v and this can be a problem. When charing in series the correct is to have a charge controller that split and control the charge individually even they are connected in series.
 

MisterBill2

Joined Jan 23, 2018
7,697
The problem with many laptop battery packs is that they are rigged so that they must communicate with the computer in order to be charged. I have a laptop that will not charge the battery unless it is powered by the OEM power supply, and it will not charge the battery unless it communicates that the battery is an OEM battery pack. Dell was very skilled at making certain that their battery systems would not charge unless all of the component pieces were OEM and in good condition.
If you can open the case without damaging anything annd add connections to each cell then you may be able to do a low-power charge of each cell and have it work. But use a very limited current and no more voltage than needed to charge at 20 mA, so as to avoid heating the battery and starting a problem.
 

Audioguru again

Joined Oct 21, 2019
2,374
I measured now a bunch of 18650 lithium-ion batteries from laptops and DVD players. I took them about 10 or 12 years ago. The red ones measure 3.7V per cell and the green ones measure only 2.5V.
 
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