Lithium ion battery charger circuit

[okbro]

hi,
will the circuit attached work to charge the 4.8V li-ion batteries in series?

 

[Papabravo]

I don't think so. Li-Ion batteries require balanced charging and other features not required by NiMH batteries.

 

[audioguru]

Your circuit does not show Li-Ion cells and it also does not show a charger circuit for any kind or battery.

Ni-MH battery cells are NOT charged to only 1.2V, instead they are charged to 1.4V to 1.5V and their voltage drops as they discharge.

Each Li-Ion cell is sold at the "storage voltage" of 3.7V and are charged to 4.2V.

What are the grey boxes on your schematic?

 

[rjenkinsgb]

will the circuit attached work to charge the 4.8V li-ion batteries in series?

No, very definitely not!
It would be very good at causing them to burst or explode....

The circuit shows a constant-current charger, which with a low enough current setting can be used for NiCd or NiMH cells, with the batteries being removed after an appropriate time. That type of cell can stand a small current for very long periods, after reaching full charge.


Charging lithium cells is more like blowing up balloons - if the current, even very small, continues after they are full, things go bang! (And burst lithium cells quite often catch fire spontaneously).


Also, as has been mentioned, if you are charging two or more cells in series, "Balance charging" is essential otherwise the burst cell situation is still possible even with the correct overall voltage.

Lithium cells must be used in combination with undervoltage/overvoltage/overcurrent protection modules, often listed as "BMS" modules.

And, for a battery pack with two or more cells, that BMS module must also incorporate cell balance.

The BMS is not a charge controller, only protection - you still need a charger with the correct voltage and current limits for the battery pack being charged.


Failing to properly charge and use lithium cells can be lethal - the energy content of fully charged cells is approximately equivalent to a quarter their weight of TNT... They may not release it quite as fast, but they can do just as much damage if misused.

 

[Nigel Goodwin]

The circuit shows a constant-current charger, which with a low enough current setting can be used for NiCd or NiMH cells, with the batteries being removed after an appropriate time. That type of cell can stand a small current for very long periods, after reaching full charge.

Doesn't it actually show a constant VOLTAGE charger, and would be bad for NiMh as well.

 

[ZipZapOuch]

What's the goal of this device? Voltage regulation, yes it will work. Battery charging? Not very well at all and possibly dangerous (depending in the protection circuits inside your lithium battery - some have none). If the circuit is for insurance fraud as you burn your house down - it mIght work but posting your question here and an investigatory seeing my replay may make it less likely to work.

 

[rjenkinsgb]

Doesn't it actually show a constant VOLTAGE charger

Oops - correct...

I can only apologise & assume it was due to me being in a pre-caffeinated state at the time!

 

[danadak]

This might be useful :

Handbook of batteries : None : Free Download, Borrow, and Streaming : Internet Archive

1 volume (various pagings) : 24 cm

archive.org

https://www.ti.com/lit/an/snva557/snva557.pdf

Regards, Dana.

 

[okbro]

yeah i think also that this circuit will not work, the IC is LM317 voltage regulator. I think I should be looking for more into these battery charger circuits.

 

[Nigel Goodwin]

yeah i think also that this circuit will not work, the IC is LM317 voltage regulator. I think I should be looking for more into these battery charger circuits.

If you're wanting Li-Ion chargers, they MUST either use a customer Li-Ion charger IC, or a suitable micro-controller controlling the charging cycle. There's no simple safe way of charging Li-Ion.