What charger to use for LI-ion batteries

[Ian Wallis]

Hello all, My old laptop battery pack died, and after removing the dead Li-ion cells I'm left with 8 usable. So to put them to good use, I have a 6 volt florescent tube type lantern I'd like to use two of the 3.6volt CGR18650AF cells in.

But what do I recharge them with?

Ideally charging from my 12 volt solar system (car battery) would be nice.

Thank you for any help you can give.

Here's a data sheet http://www.houseofbatteries.com/documents/CGR18650AF.pdf

 

[Alec_t]

Welcome to EP!
Lithium batteries are fussy and need a particular charging profile if they are to be charged safely. If charged wrongly they can catch fire or explode.
Have a read of this.
There are special-purpose ICs available for safely controlling the charge profile.

 

[kellys_eye]

The 18650 is a 'generic' Lithium, very commonly used these days and there are dedicated chargers for them as well as simple circuit board modules for charging them singly, in pairs, in series etc.

Google '18650 charger' and see what comes up.

 

[Ian Wallis]

Thank you for the info guys. Silly but I just didn't realize Joe public used these Lithium batteries, as all I ever see is AA nickel metal hydride.
Anyhow ebay's a wash with everything that I would need, a 12 volt car charger for 99p Sorted, Cheers.

 

[WHONOES]

Li-Ion cells have to be charged in a similar manner to sealed Lead Acid batteries.
This is a 3 term process.
The charge voltage should be set depending on the construction of the battery. Those with cathodes of Aluminium, Cobalt, Nickel or Manganese require 4.2V per cell though some Nickel based varieties will require just 4.1V per cell.
The 3 term process is constant current then constant voltage followed by a maintenance charge.
The constant current part is to prevent excessively large amounts of current being dumped into your depleted battery which would cook it in no time at all and would most likely catch fire. A value of 0.5 to 1 times cell capacity would be required.
Then as the cells accrue charge they will come to a point where the current will start to diminish whereupon constant voltage charging takes over.
When charge current drops to 10% or so, the charge voltage would be reduced to the cells nominal voltage which provides the maintenance aspect of the process.
This probably sound like a design nightmare but is actually quite simple to implement.

 

[kellys_eye]

This probably sound like a design nightmare but is actually quite simple to implement.

Anyhow ebay's a wash with everything that I would need, a 12 volt car charger for 99p Sorted, Cheers.

 

[WHONOES]

Don't use a 12V car charger it is not up to it.

 

[kellys_eye]

Don't use a 12V car charger it is not up to it.

Why not?

A single 18650 is only needs a 4.2V (give or take) charge voltage and a module powered from 12V would have no difficulty with that.

 

[WHONOES]

Yes but, you still need to regulate the output volts to 4.2V per cell.

 

[kellys_eye]

Yes but, you still need to regulate the output volts to 4.2V per cell.

The OP's reference was to an 18650 charger that operated from a 12V source....

 

[BobK]

The OP's reference was to an 18650 charger that operated from a 12V source....

Or, at least we can hope so.

Bob

 

[Audioguru]

My 18650 Lithium Ion cells from a laptop are name-brand (Panasonic) and are rated at 3000mAh (3A).
I adjusted an LM317 regulator to an output of 9.1V and it has a 1N4002 rectifier diode in series with its output so that the circuit output is 8.4V. It is powered from a 12VDC/1A wall wart. Two of the cells replace four Ni-Cad cells in a portable vacuum cleaner and I charge the lithium cells overnight when the vacuum cleaner runs slow.