Lithium-Ion Cells Charger Using Dead Laptop Batteries ... - Page 1
Forum section: electronics / beginners

author: battery13v
author_rank: Contributor
timestamp: May 09, 2016, 03:11:21 pm
content: So Hi everyone ... i want to make a lithium-ion charger using the laptop batteries circuit boards ... but i searched the internet and i did'nt find any information cocerning this porject ... i'm a beginner and most the ICs in the circuit board don't have Datasheets in the Internet so i want to know :1- How a laptop charge the battery in details please ... how much voltage enter in the circuit board ?2- How the circuit board charge this cells and how could i control it's charging ... like if i want to charge just 2 cells or 16 cells you see !!and Thx A lot for your help !?

author: mikerj
author_rank: Super Contributor
timestamp: May 09, 2016, 05:56:56 pm
content: Those are protection circuits that are fitted inside laptop battery pack. They are responsible for preventing the cells being exposed to damaging voltage levels (under and over-charging) and also monitor battery capacity for the battery "gas gauge". They are not responsible for actually charging the battery (i.e. providing the the constant current/constant voltage phases) there will be a circuit within the laptop itself that does this.

author: sjd.aliyan
author_rank: Contributor
timestamp: May 09, 2016, 06:29:40 pm
content: Quote from: battery13v on May 09, 2016, 03:11:21 pmSince you didnot mention any information about your battery i told you in general:-this type of batteries use SM-Bus to charge (smart batteries)-this type of batteries dosen't have charger inside them and charger ic is on the motherboard of laptop,battery only have a few chips for over-voltage protection and in some batteries and eeprom that keeps cycles of battery-most usual topology of laptop batteries is 6cell (3 series of 2 parallel cells)mostly 10.8-11.1v (actual voltage is dropped during discharge)Charging cycle of li-ion battery has 2 modes:1.Constant current (CC):usualy 0-70% of charging cycleIn this mode battery voltage would be between 2.4-3.32.Constant voltage (CV):70-100% of charging cycle3.3-3.9 or even more than 4This is how you could determine percent of charge in cell,by measuring voltage of battery.once you put battery in circuit for example put a resistance between +and- current flows and resistor become hot and voltage of battery drops (it called voltage drop)you can determine life of a bettery by connecting a load and measuring voltage drop of battery if voltage drop was too much it shows that battery is not in a good condition.one important thing about current and amperage of battery is charging rate and discharging rate defines with C(C is a number that multiplies in battery capacity and shows how fast you can discharge the battery)li-ion cells usually cant discharge faster than 2c.for example you can discharge a 3000mah battery with only 6amp (2*3amp)you could not charge or discharge too fast in this case cell would become hot,dangerous and will explode in couple of minutes.you can read batteryuniversity.com for more details about batteries.

author: Audioguru
author_rank: Super Contributor
timestamp: May 09, 2016, 10:34:56 pm
content: Don't you think that most "dead" laptop Lithium batteries are thrown away because they are finished and do not work anymore?My daughter threw away her first laptop when she soon bought a much better one and I salvaged the good cells from its battery. I use two of its cells in a little portable vacuum cleaner.

author: Rick Law
author_rank: Super Contributor
timestamp: May 09, 2016, 11:01:31 pm
content: Quote from: Audioguru on May 09, 2016, 10:34:56 pmI think most "dead" laptop batteries are sold by scrap yard to recyclers whole-sale than trickles it way back to flash lights, drills battery packs...Even when the battery is just a shell (ie: dead as a door nail, can't hold charge, parrots in a British TV show, etc., etc., ... stone dead), you will still find buyers for the shell because they will find someone who will put it in their system for someone even more dumb to buy it.

author: Audioguru
author_rank: Super Contributor
timestamp: May 10, 2016, 12:37:56 am
content: Quote from: Rick Law on May 09, 2016, 11:01:31 pmIsn't ebay and Amazon the recyclers who sell that non-working garbage?

author: battery13v
author_rank: Contributor
timestamp: May 10, 2016, 02:33:32 am
content: Quote from: The_Almighty_Bacon_Lord on May 10, 2016, 01:31:55 amOk this is a good step forward ... thx a lot ... and i'm trying with it ... in the same time i'm also waiting for someone who is an expert to provide us with some tricks ....If someone could provide us with an image of the charging IC in Laptops it's a good thing

author: rstofer
author_rank: Super Contributor
timestamp: May 10, 2016, 03:12:47 am
content: Quote from: battery13v on May 10, 2016, 02:33:32 amGoogle is your friend, just search for 'li ion battery charger chip' Among other replys:http://www.ti.com/lsds/ti/power-management/battery-charger-ic-products.pageThere are literally hundreds of devices spread across a lot of manufacturers for various capacities and chemistries.

author: amyk
author_rank: Super Contributor
timestamp: May 10, 2016, 10:47:30 am
content: Quote from: sjd.aliyan on May 09, 2016, 06:29:40 pmEvery time somebody brings up that site, I feel compelled to post this:https://www.eevblog.com/forum/projects/diagnosing-lithium-cells/Lots of good info in that thread.