Li-ion battery charger/controller ic - Page 1
Forum section: electronics / beginners

author: speedster
author_rank: Newbie
timestamp: February 04, 2014, 02:30:41 am
content: Hello.I want to build a Li-ion cell battery charger for six nice Samsung ICR18650 26F cells I have, and charge them either individually, or in pairs, using one of the dedicated Li-ion charger ic's available on the market.This is the battery cell datasheet:http://www.produktinfo.conrad.com/datenblaetter/250000-274999/251024-an-01-en-LiIon_AKKU_SAMSUNG_ICR18650.pdfAccording to the manual these cells can be charged up to max 1C, with an ending relative capacity of 90%, as a trade off. 1C equals 2600mAh, so for the CC (constant current) operation of the charging process, the charger must feed the cell with 2,6Amps for a certain period of time. Is this value the "Charge Current (Max) (A)"? I mean, does the charger chip its self has to be able to handle 2,6Amps of output current? But, since some ic's are capable of only 15mA, and even less, I'm guessing that this in not the case, and the output current is driven into an external circuitry, or not?Actually my question might be a lot simpler: How can a big Li-ion cell be charged, or be fast charged? Is there a "suitable" chip for my case?All answers are welcomed.Thanks

author: lapm
author_rank: Frequent Contributor
timestamp: February 04, 2014, 05:04:35 am
content: Charging chip usually in high current situations drives separate power driver. And IC itself mainly adjusts charging current throw this power driver. Some what similar to electrical dummy load...How ever being Li-ion stuff read all datasheets very very carefully. Design your charger even more carefully. Otherwise you might create something that burns down the house.I believe our very own Dave Jones has video on youtube about Li-ion battery charging...

author: bhilly82
author_rank: Contributor
timestamp: February 04, 2014, 05:54:46 am
content: are you dead set on making your charger? If not have a look at this DC chargerhttp://www.hobbypartz.com/60p-dyc-1004.htmlif your in the usa this is a great choice as it will charge any kind of battery safely and the price is fairly low considering the cost of the cells you are buying.

author: Neilm
author_rank: Super Contributor
timestamp: February 04, 2014, 06:27:43 pm
content: I've used the TI chip BQ24600. It drives a pair of FETs that are used to switch the current. Reasonably easy to configure - you just follow the examples in the datasheet to programme the charge current and end voltage and it pretty much does the rest.

author: speedster
author_rank: Newbie
timestamp: February 05, 2014, 10:15:51 pm
content: It's been a couple of days now, and I really can't find the correct charger. Only a dozen of ic's seem to be able to handle currents over 2A. And if I start adding parameters (5/12V supply, linear mode) they options become even less. The "good" ones are QFN packages, which are extremely small for me. I was amazed to discover that some manufacturers offer "through hole" charger chips to the same size of a 555 timer, but they turned to be old design, at 4.1V, requiring a generous amount of external components.How do you guys charge 18650 cells? Really?If someone can guide me to a separate power driver circuitry would be much appreciated.Is it a common practice to include a Breakout Board to your final product? It is ugly for sure, but is it ok ?Thank you very much!

author: sleemanj
author_rank: Super Contributor
timestamp: February 05, 2014, 10:39:20 pm
content: I've seen TP4057 IC's run in parallel on the cheap charger boards on ebay, and have anecdotally heard of people running TP4056 charger boards in parallel... you should grab a couple off ebay and do some tests to see how well they work in parallel.The T4056/7 are available for a few cents (from China vendors), and needs very minimal components (56=1Amp, 57=500mA)

author: speedster
author_rank: Newbie
timestamp: February 06, 2014, 12:31:53 pm
content: Thanks for your comment sleemanj. Parallel connections in power applications frighten me, moreover I don't have the equipment to test, monitor or investigate, yet, unfortunately. I would also prefer to do it the "proper" way, and use a suitable chip. By the way, my local supplier warned me that he's not going to offer any kind support if I mess with Chinese ic's and crappy datasheet

author: amyk
author_rank: Super Contributor
timestamp: February 06, 2014, 12:41:04 pm
content: Simplest way to charge an 18650 would be a 4.2V (or lower if you want to extend life at the sacrifice of capacity) supply current-limited to the maximum charge rate.