Li-ion battery charging

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palesha

Joined: 16 Apr 2001
Posts: 149
Helped: 5

28 Mar 2004 15:34 Li-ion battery charging

I want to make transistorised Li-ion battery chrger for mobile phone. The Li-ion battery is 800mAh for samsung cdma cell phone.

House_Cat

Joined: 21 Feb 2002
Posts: 1507
Helped: 307
Location: USA

29 Mar 2004 0:07 Re: Li-ion battery charging

This is not a project to take on lightly. If you don't know exactly what you are doing, you can damge the battery and/or cause the battery to go into thermal runaway and explode or burn.

A Li battery charger needs a monitor circuit to ensure that the following is met:
-Reverse polarity protection
-Charge temperature--must not be charged when temperature is lower -than 0° C or above 45° C.
-Charge current must not be too high, typically below 0.7 C.
-Charge voltage--a permanent fuse opens if too much voltage is applied to the battery terminals
-Overcharge protection--stops charge when voltage per cell rises above 4.30 volts.
-A fuse opens if the battery is ever exposed to temperatures above 100° C.

If you are determined to try it yourself, there are a number of integrated solutions that are used in chargers. Take a look for application notes that will give you some suggestions. Datasheets for one manufacturer are at:

http://www.national.com/parametric/0,1850,2362,00.html

Fom

Joined: 10 Mar 2004
Posts: 778
Helped: 57
Location: Taiwan

29 Mar 2004 2:05 Re: Li-ion battery charging

I agree with House_Cat. I just would like to say that every Li-Ion battery for mobile phone already has internal protection for overcharge, overdischarge, loading overcurrent and shortcurrent. But anyway another protection from charger side doesn't hurt.

spauls

Joined: 17 Dec 2002
Posts: 547
Helped: 19

29 Mar 2004 16:21 Re: Li-ion battery charging

Li Battery are prone to ESD ,
so i am not sure how u make it in lab

Externet

Joined: 29 Jan 2004
Posts: 83
Helped: 3

29 Mar 2004 16:36 Re: Li-ion battery charging

Hello.
A Li-ion battery charger is nothing else but a plain DC power supply. Inside the battery pack resides all the control, regulation and protection circuitry.
That is why to charge a cell telephone from an automobile 12V only a cable is used.
A Li-ion cell charger is a regulated 4,1000 V or 4,2000 V [depending on the cell chemistry and brand] supply.
The positive terminal of the cell has a rupture type aluminium disc diafragm theat serves both as a overcurrent fuse and an overpressure vent.
In order to charge a Li-ion cell, just obey the critical maximum voltage with a high precision voltmeter.
You can transistorize the chargers if you want.
Miguel

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29 Mar 2004 16:36 Ads

palesha

Joined: 16 Apr 2001
Posts: 149
Helped: 5

29 Mar 2004 19:41 Re: Li-ion battery charging

Herewith attached one circuit given by my friend of his mobile charger for same cellphone purchased from open market. I think it must be chinese, Comments on this circuit required. [/img]

Sorry, but you need login in to view this attachment

cube007

Joined: 12 Mar 2002
Posts: 538
Helped: 12
Location: Australia

29 Mar 2004 20:27 Li-ion battery charging

Hello,

There are some very important information about the use of Li-Ion cells at: http://www.panasonic.com/industrial/battery/oem/chem/lithion/index.html

Bye,
cube007

Externet

Joined: 29 Jan 2004
Posts: 83
Helped: 3

30 Mar 2004 16:43 Re: Li-ion battery charging

Hi palesha.
That circuit makes no sense to me.
What is the current path from input +VE to output +VE ???... Trough transistor base ???
Crying or Very sad

Miguel

Fom

Joined: 10 Mar 2004
Posts: 778
Helped: 57
Location: Taiwan

31 Mar 2004 2:30 Re: Li-ion battery charging

Not every battery pack for mobile phone includes charge overcurrent protection. Battery manufacturers only start to include this function into battery. Recommended current rate 0.6C. With this rate battery is not overheating during charge time. Overheating above 60 C can cause permanent loss of capacity. Charger operates in constant current mode and monitors battery voltage. When voltage reaches certain value -4.2 V charger changes it's mode to constant voltage and monitor current. Current will be gradually decreasing. When it will be lower than 0.1C you can stop charging.

hadihf

Joined: 29 Mar 2002
Posts: 136
Location: Planet Earth

31 Mar 2004 6:20 Re: Li-ion battery charging

Hi,
Read these and I think you will like it Very Happy

http://www.rcgroups.com/forums/showthread.php?s=41425c030ffb32d0053dc684abb2e98b&threadid=130567

http://www.rcgroups.com/forums/showthread.php?s=41425c030ffb32d0053dc684abb2e98b&threadid=212232

Regards

lguancho

Joined: 07 Jan 2004
Posts: 266
Helped: 5
Location: Singapore

12 Apr 2004 10:50 Re: Li-ion battery charging

If you are going for regulatory testing for your mobile phone, the test house will ask for your battery charge, for safety/emc testing.

Do pay attention to charger, get it from reliable source, with proper safety test done (CE mark). This thing can explode if it is a low cost design, with poorly engineered PCB design. You don't want to land yourselve into trouble after selling thousands of these "bombs" into the market Cool

ayeong

Joined: 01 Jan 1970
Posts: 99

12 Apr 2004 11:20 Re: Li-ion battery charging

If your volume is huge and space constraint, may as well go for a single chip & single-cell lithium ion standalone charger.

You may refer from texas instrument BQ24010
http://focus.ti.com/docs/prod/folders/print/bq24010.html

Linear Technology (LT4058)
http://www.linear.com/prod/datasheet?datasheet=1019&product_family=power

Cheers,