18650 beginners guide/introduction - Page 1
Forum section: electronics / beginners

author: nemail2
author_rank: Regular Contributor
timestamp: November 20, 2018, 07:35:35 am
content: Hiis there any beginners guide or introduction in 18650 cells you can recommend?I have salvaged some of them (Sanyo) and would like to use them for my projects but I also don't want them to catch fire or explode in my hand. I'm very aware of the danger those batteries carry within them, that's why I'm asking for advice here.I know that shorting them and charging them with too much current is not good.Do I always need a charging controller or can I charge them using constant current with my Lab PSU as well? How much current, are they all the same or does it depend on the manufacturer/part number of the 18650?Also I heard of balancers which I need if I want to charge two or more cells, are they connected in series or in parallel then, does that even matter?Are there basic circuits or ICs which practically everyone uses (general purpose parts) which I should take a look at?Thanks!

author: spec
author_rank: Frequent Contributor
timestamp: November 20, 2018, 09:13:48 am
content: Hi nemail2,Quote from: nemail2 on November 20, 2018, 07:35:35 amLook up 'Battery University' on the net:https://batteryuniversity.com/learn/article/types_of_lithium_ionQuote from: nemail2 on November 20, 2018, 07:35:35 amSanyo, now Panasonic, are one of the best manufacturers of batteries, so you are off to a good start.Quote from: nemail2 on November 20, 2018, 07:35:35 amThe dangers of LiIon batteries are often greatly exaggerated, especially on some forums.Your batteries are almost certain to be lithium/cobalt chemistry (LiCoO2), which presently has the highest capacity/weight ratio on the market. LiCoO2 is also the cheapest.But, one downside of LiCoO2 is that if it overheats it can get into a thermal runaway situation where the more heat it generates, the more heat it generates. But the manufacturers are aware of this and house the battery in a substantial case with blow off vents to allow any excessive gas pressure to escape.The other thing to bear in mind is that we are surrounded by LiCoO2 batteries. They are in mobile phones, laptops, battery power tools, electric cars, E-cigarettes, and so on. And in many of these devices the batteries have a hard time. That is why they don't last very long.Quote from: nemail2 on November 20, 2018, 07:35:35 amJust like any batteryQuote from: nemail2 on November 20, 2018, 07:35:35 amIt is far better to use a dedicated charge controller, but you can charge your batteries with a lab power supply set to no more than 4V, and no more current limit than capacity/10. 200mA would be safe for all 18650s.(UPDATE 2018_11_21) Depending on your lab PSU design, there is a danger of back flow if the power supply is turned off while the battery is still connected. So best to put a switch between the battery and the power supply to cater for this. Then ensure the switch is off, turn the PSU on and connect the battery to be charged. Once charging is complete, turn the switch off first.Quote from: nemail2 on November 20, 2018, 07:35:35 am18650 only refers to the case size: 18mm diameter, 65mm long. There could literally be anything in the case, but generally it is LiIon of some flavor.The earlier LiIon 18650s had a maximum capacity of around 1AH, but in 2018 the maximum capacity is around 3.5A, that is from first tear manufacturers like Panasonic (Sanyo), LG, Sony, Varta. Makes, other than first tier, should be avoided.Like most electronic devices, the manufacturer will have a part number for their batteries and related specification sheets. If you don’t have the manufacturer's part number, the only way to determine battery capacity is to test it at 200mA constant current load. I would guess though, that your batteries would have a capacity of around 1.5AH.Quote from: nemail2 on November 20, 2018, 07:35:35 amYes, in seriesQuote from: nemail2 on November 20, 2018, 07:35:35 amThere are common charger chips, but they are not basic. They are readily available, and dirt cheap though

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: November 20, 2018, 09:55:21 am
content: Get some cheap Chinese 18650 batteries that are filled with sand and you won’t need to worry about any explosions

author: spec
author_rank: Frequent Contributor
timestamp: November 20, 2018, 10:52:12 am
content: Quote from: Sudo_apt-get_install_yum on November 20, 2018, 09:55:21 am

author: Whales
author_rank: Super Contributor
timestamp: November 20, 2018, 11:09:07 am
content: Quote from: spec on November 20, 2018, 09:13:48 amMake that 4.2V, not 4.6V!There are enthusiast forums dedicated to batteries -- checkoutcandlepowerforumsfor all sorts of guides, horror stories and the likes.

author: Peabody
author_rank: Super Contributor
timestamp: November 20, 2018, 02:53:59 pm
content: Don't forget Dave's video on charging with a PSU:

author: spec
author_rank: Frequent Contributor
timestamp: November 20, 2018, 07:48:41 pm
content: Quote from: Whales on November 20, 2018, 11:09:07 amDid you read the rest of that part where I say to connect a diode between the PSU and battery to give a battery charging voltage of 4V? Or are you saying that the battery charging voltage should be 3.6V?

author: Whales
author_rank: Super Contributor
timestamp: November 20, 2018, 11:02:58 pm
content: Hmm, no I didn't.Not a fan of this diode method. Overcharging would take a long time, but would still be possible.

author: spec
author_rank: Frequent Contributor
timestamp: November 21, 2018, 02:07:54 am
content: Quote from: Whales on November 20, 2018, 11:02:58 pmAh I see. Now that you have actually given the basis of your statement, I will have a look at the diode approach in detail.Have you tried charging a LiIon battery with 4.6V through a diode (not schottky) and found that the battery voltage exceeds 4.2V?It is ironic, because I have been in your corner on another forum and been persuaded that the diode approach is OK.But in the meantime, I will amend my post, which I have not had time to finish/review.

author: mtdoc
author_rank: Super Contributor
timestamp: November 21, 2018, 02:15:50 am
content: A good resource isthis book. It has lots of good info about lithium batteries - not just 18650s.

author: Rick Law
author_rank: Super Contributor
timestamp: November 21, 2018, 03:24:06 am
content: Besidecharge protection, you also needover discharge protection.If your battery is over-discharged to say 0.0V, your battery is dead. In fact, discharge to below 2.6V is not healthy for a LiIon battery. Reviving a 0V battery is possible, but it would be like reviving a race-horse and the horse can now limp with 2 legs while dragging the other two.Search the web, you will find "battery protection modules." They typically cut out at 2.4V-2.6V and don't let the battery discharge below that. Some battery protection modules also protect against shorts (over current), over voltage charging, etc.

author: spec
author_rank: Frequent Contributor
timestamp: November 21, 2018, 04:49:02 am
content: Quote from: Rick Law on November 21, 2018, 03:24:06 am"race-horse"You read on the web that if you try to charge a LiIon battery that has a terminal voltage of less than xV that they will explode, you will be killed, your house will burn down, and the world will end. People just love to be dramaticBut you just said that the battery would be fatally damaged.I would suggest that the situation is not even as bad as that. Perhaps the wording should be, 'if you let a LiIon battery terminal voltage drop below the battery manufacturer's specification, you stand a chance of degrading the battery'.One problem with a low terminal voltage battery is that most dedicated LiIon battery chargers will refuse to charge them, often with dire warnings, so you have to bring the terminal voltage up manually with a constant current from another source. Once the terminal voltage has risen above the lower limit you can then put the battery on a normal charger to complete the charge.About the damage done to a LiIon battery with a low terminal voltage. For a start it is obviously not advisable, because the manufacturer says so, and they are the authority. There can be no argument there, but what about practice.To start with, I have often wondered how the battery manufacturers make LiIon batteries without burning the factory down. When they first make a LiIon battery, isn't the terminal voltage 0V by definition? I must admit that I have not looked into this and may have missed a fundamental point. Perhaps a battery manufacturing expert can advise.Over the years I have been involved with batteries and chargers of pretty much all types. And I have done many experiments, including discharging LiIon batteries below the cut off point and also over charging them above the specified voltage. In most cases it made very little difference to the subsequent battery performance. But it does depend on how long the battery is kept at a low terminal voltage and all the experiments were done with a charging current of capacity/10.In one experiment 10 LiIon batteries were left for a year at a below recommended voltage. After a year, the batteries were given three normal charge/discharge cycles and every battery performed normally. Also, I regularly pull 18650s from laptop and power tool packs and the batteries are in all states of charge and terminal voltage. But after three charge cycles most recover, apart from the one battery that failed and made the pack unusable.Of course the terminal voltage is important, but equally important is charge current and ultimately the limiting factor, as with most electronic components, is internal temperature.Just briefly, because I may cover this aspect in my original post: there are various LiIon battery charging regimes, ranging from aggressive to benign. An aggressive regime is high current charging, high terminal voltage and low cut-off voltage. This is the regime used in many consumer products, especially mobile phones, laptops, E-cigarettes, and battery powered tools, because long battery duration and fast charging are key selling points. But it is a triple whammy and gives the battery a hard time. As a result, they do not last long.At the other extreme you get a benign regime as used in Tesla electric cars for example. And the reason is that Tesla guarantee their batteries so they cannot afford to sacrifice battery life. A typical benign regime would be to charge to 4V and discharge to 3V. With this regime you would get around 70% to 80% of capacity, but a vastly longer battery life.The point of all this, is that there is a lot more to LiIon batteries than never exceeding a terminal voltage of 4.2V and never going below 2.7V.

author: 6PTsocket
author_rank: Regular Contributor
timestamp: November 21, 2018, 07:12:30 pm
content: Another thing to note if buying new cells, some are slightly longer than 65mm because they already have the protection module built in. This also detirmines the maximum discharge rate for that cell. You will see cells listed as protected and unprotected in places like the Battery Junction catalog. If you are building your own multi cell pack there are control boards for various numbers of unprotected cells. See ebay for an idea of what is out there.Sent from my SM-G900V using Tapatalk

author: nemail2
author_rank: Regular Contributor
timestamp: November 21, 2018, 09:31:59 pm
content: Hi,thanks for all your replies!I have these batteries, unfortunately I didn't find anything on the internet about them.They seem to have some balancer board integrated. The red one is the same as the black one but without the outer plastic (I removed that).https://owncloud.ne-mail.net/s/3jmTYBpdpfx8J2X/download?path=%2F&files=20181121_222438.jpghttps://owncloud.ne-mail.net/s/3jmTYBpdpfx8J2X/download?path=%2F&files=20181121_222445.jpghttps://owncloud.ne-mail.net/s/3jmTYBpdpfx8J2X/download?path=%2F&files=20181121_222455.jpgWill have to read everything a few times and google more and watch the video to master the batteries eventually and build my first practical things up (like DC-DC converter (step up/down) for powering things).

author: thm_w
author_rank: Super Contributor
timestamp: November 21, 2018, 10:23:36 pm
content: That is good they have the protection circuitry already installed, I would leave it in place and use the pack as is.Probably provides overcurrent and over/under voltage protection already (you can see some control IC and a mosfet switch).

author: Terry01
author_rank: Frequent Contributor
timestamp: November 21, 2018, 11:03:19 pm
content: https://secondlifestorage.com/index.phpTry this buddy.https://secondlifestorage.com/celldatabase.phpHere is some info on the cells

author: Rick Law
author_rank: Super Contributor
timestamp: November 21, 2018, 11:20:24 pm
content: Quote from: nemail2 on November 21, 2018, 09:31:59 pmThey looked exactly like the Sanyo's I got out of a Fujitsu laptop. But red skin is not uncommon so they could be entirely different still.If you look very closely on the red skin, there arevery faintdot matrix ink jet printed numbers and letter on it on the side. Look at my first picture , the one with only 2 cells, the top one doesn't have clear plastic cover. Right at where the "6" is (where I consider batteries' top), look about 2/3 of the way down (away from the "6"), you may find the faint numbers there. On the bottom one, I have also installed a "protection board" (aka PCM).From my research back when I first recovered them, they are 3.6V and not the typical 3.7V (the labels shown in the picture were wrong). I lost my note book, so I am not sure how I got that. I think I got the voltage from label on the laptop battery pack - the nominal total wattage/capacity and the list voltage.They are pretty good cells (comparing to others of the same vantage I've recovered).For half of them, they held to their nominal pretty good and delivers a good punch. But I killed one of them by over-discharging them to below 2.4V (tested it before I install the PCM, and left it running all night, it was 0.0V in the morning). It dropped from 2200mAH to about 400mAH after I "revived" it.If your's are the same, check your first charge carefully (as you should always do anyhow). I've a few that got hot after a while. I left those alone without PCM, but I have not dispose of them yet. I forgot about them, actually.I took a second picture with 3 cells, I have labels which I want you to see (get hot) - I was not kidding about them possibly getting hot. It is so close up that the closer one looks bigger than the others but that is just optical illusion. Again, the voltage on them are wrong - 3.6V and not 3.7V.

author: Jwillis
author_rank: Super Contributor
timestamp: November 22, 2018, 11:48:49 pm
content: Quote from: Rick Law on November 21, 2018, 11:20:24 pmI wouldn't worry to much since Sanyo acquired Fujitsu and both were acquired by Panasonic .All three brands are likely made in the same plants.