How fast can you charge a 18650 - Page 1
Forum section: electronics / projects

author: antoniobeta
author_rank: Contributor
timestamp: January 25, 2018, 10:21:50 pm
content: Hi guys.I have a pair of Samsung 26J, on their datasheet it says that those batteries can be charged up to 2c.The batteries have a capacity of 2.6A/h, so with the maximum charging rate of 2c they could be charged in 30 minutes.I am thinking about boots that carging current up to 15amps, which would be 6c and the cell would be charged in 10 minutes.I know that for using those high currents for charging me would have to cool very well the battery, I am thinking of using a pair of peltier cells.Could it work?

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2018, 07:50:20 am
content: Follow the datasheet. If the datasheet says that 2C is the max charge rate then 2C is the max charge rate, no matter what temperature the cells are. If you charge at 6C it will either outgas and fail or it will blow an internal fuse designed to prevent catastrophic failure.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 26, 2018, 08:26:15 am
content: Follow the max charge rates. Even that 2C spec most likely results in reduced cycle life. And you won't get from empty to full in 30 minutes, since at current that high, you hit 4.2V at around 80-90% SoC, after which you enter CV, slowing down the charge rate. In 30 minutes, you would be at around 90%.Li-ion charge/discharge rates are asymmetrical.Excessive charging current causes lithium plating, which doesn't happen at discharge. It's not a thermal thing as much, since much higher rates are OK for discharge. Actually trying to cool the cell down too much causes even more lithium plating - optimum cell temperature for high-speed charging is around 40-50 deg C.

author: Terry01
author_rank: Frequent Contributor
timestamp: January 26, 2018, 08:31:07 am
content: You could maybe even boost it up to 30A so long as you give it a good blow too, so long as your sucking an ice cube while you blow!Oh wait....blow....suck....hmmm.....BOOM!!!Don't do it my friend....it's not big.....it's not clever...and it certainly won't work!!

author: drussell
author_rank: Super Contributor
timestamp: January 26, 2018, 08:32:27 am
content: Huh?You say, "I have this cell that says I should charge at maximum 2C. Should I charge it at 6C?!"Is this a troll?

author: Terry01
author_rank: Frequent Contributor
timestamp: January 26, 2018, 08:35:03 am
content: It was a troll....now it's just a pair of smoking shoes!

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 26, 2018, 09:34:03 am
content: Of course Samsung would have said so in the datasheet if they thought that his batteries can be recharged at 6C.A Tesla S100 can be recharged at max 1.2C (100kWh batt @ 120kW), a Hyundai Ionic EV at max 3.5C (28kWh batt @ 100kW), and an Antonio's mistery device @ 6C? No, no, don't do that!In any case you can only charge at those CC rates up to ~80%, from there to 100% it's at a lower rate (CV), so even @6C it was not going to be 10 minutes from empty to fully charged.

author: Damianos
author_rank: Frequent Contributor
timestamp: January 26, 2018, 10:20:35 am
content: Quote from: antoniobeta on January 25, 2018, 10:21:50 pmYour approach does not seem easy to implement, because you need to use very powerful Peltier cells, installed inside the batteries!Another way to do fast charging is to use a current more than 100C, so the batteries will charge is seconds, not having the time to increase the temperature!

author: Jeroen3
author_rank: Super Contributor
timestamp: January 26, 2018, 11:39:57 am
content: Relevant videos.

author: BravoV
author_rank: Super Contributor
timestamp: January 26, 2018, 12:30:34 pm
content: When it comes to Li-Ion cells, have a respect if you care about your safety.Do what the manufacturer said on how to treat "THEIR" manufactured cell, those written instruction was made for a reason, never ever ignore it.Imagine it explodes right in front of your face with just a tiny metal shrapnel flew to your unprotected eye, your life could be different from that minuscule stupid moment.https://youtu.be/Svyv8jgwq0Y

author: Jeroen3
author_rank: Super Contributor
timestamp: January 26, 2018, 12:54:49 pm
content: Storing energy in small volumes has it's dangers. This is why Samsung pushed crippling firmware to their Note 7.