Charging an old laptop battery

[VK3ZYZ]

I have a number of laptop batteries that are not completely dead. This one, for instance, from a Toshiba.
After opening it up and finding no cells at 0V, an attempt to charge in it on a cell balancing charger did not work. So, for the last couple of weeks, when I have my radio on, the cells were slowly trickle charged from the 12V via an LED, diode and 1K resistor. The idea was to get the cells up to a voltage the charger would work with. They all were about 3.2V after this treatment.

Today I tried it again and it is now charging

If this works ok, I will make up some battery packs from the old cells so some of my radios may be used portable.

 

[VK3YNV]

By some cosmic co-oincidence, Big Clive has just done a video on charging lithium ion batteries.

The modules are pretty good value from ebay you get 10x for $A13.38 so about $1.30 each.

AU 5x TP4056 1A lithium battery charging board module 1A with protection TYPE-C | eBay

B+ is connected to the positive side of the lithium battery, and B- is connected to the negative side of the lithium battery. Large charging current: 1000mA. Input with TYPE C USB socket. Battery overcurrent protection current: 3A.

www.ebay.com.au

 

[VK3ZYZ]

Yes, I have some of those and they are great. As he says, get the better ones with the discharge protection as shown in the video above.

 

[VK3ZYZ]

It looks like the battery has come up ok

Cell volts = 4.20, 4.20 and 4.18V

 

[VK3YNV]

I have to build a couple of portable packs for testing irrigation actuators. So I'm using the CF-4S30A-A protection board.
They are left over from another project, so I have a few spares if you want a couple.

 

[VK3YNV]

Back on the 4S 18650 pack I'm using a 20V laptop plug pack to do the charging, just because I have a few available.
So I need to regulate that down to something less than 16.8V ( 4.2x4) so I decided to aim for 16.4V that's 4.1V per cell,
The balance charger board takes care of the rest like cell balancing, low voltage cut off etc.

Denys did a SMPS replacement for a 3 terminal regulator, which uses the LM2675 adjustable simple switcher. So calculating the resistor values
if I use R2=12K, R1=1K + 47K +47K, I end up with 16.395 Volts out, which should be fine. Very handy little board, talk to Denys if you want some.