Author Topic: used 18650 in series and parallel - opinions.  (Read 2908 times)

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Simen

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used 18650 in series and parallel - opinions.
« on: June 26, 2017, 01:19:11 AM »
I have 12 pc. 18650 Lithium cells, 2 different brands, which i am going to use in a powerbank. I'm going for 2S, 6P configuration.

One set of 6 cells have a capacity of around 2100 mA, and the other set, around 2250 mA. The internal resistance of each cell are all around 100 mOhm +/- 10 mOhm.

Question is; should i use all from each brand in its own parallel-string, or should i mix 3 cells from each brand in each parallel string to even out the capacity?

I will of course use a balancing bms board to protect the cells...
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

frackers

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Re: used 18650 in series and parallel - opinions.
« Reply #1 on: June 26, 2017, 05:42:18 AM »
Lithium are more voltage than current or capacity sensitive. If they are the same chemistry then they'll be fine in parallel.

I'd recommend undercharging them at 4.1 volts maximum rather than 4.2, they will last longer even though the capacity will be down by about 5%.

A mate is building packs into old ice cream containers that hold 64 cells per box, he charges to 3.8v (half capacity, 10 times the cycles) and expects to get another 1000 cycles at least from these second hand cells (ex-laptop) that he has tested and checked the capacity of. He has a full 48v worth now which gives him over 3kw-hrs of storage for pretty much nothing (apart from the testing gear).
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Simen

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Re: used 18650 in series and parallel - opinions.
« Reply #2 on: June 26, 2017, 06:19:53 AM »
Thanks for the answer. :)

I'll have to see how well, and at what voltages the bms i've ordered (from ebay/china), balances the cells; if the balancing happens continuously, i can set the charger at a lower end-voltage, but if balancing only happens when one of the cells reach 4.20 Volt, i'll stick with that. ;)

The cells i have are also from laptops; unused - but stored on the shelf too long (Thus, free for me. ;) ) When i got them, they had a resting voltage at 1.1-1.6 Volt, so i charged each cell to 3.2 Volt with only a few mA's, before full charge... They should be 2600 mA cells, but resting at undervoltage have reduced the capacity.

They usually gets a little better capacity after a few cycles.
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

OperaHouse

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Re: used 18650 in series and parallel - opinions.
« Reply #3 on: June 27, 2017, 10:11:22 AM »
6P is a lot of energy.  There is always a chance that one cell will short. I don't like to put more than 2 in parallel without a fuse for each pair.  So, three fuses for every 6 cells.  A 5-8A would be sufficient to prevent a catastrophic failure. 5 cells feeding into one shorted one would be a real hazard.  I'm always dealing with recycled cells wit a more likely failure rate.

Simen

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Re: used 18650 in series and parallel - opinions.
« Reply #4 on: June 27, 2017, 01:18:22 PM »
Not a bad idea. :)
But wouldn't 2 fuses for each 3 pair be enough? (Between pair 1-2 and 2-3.) The rest should the bms manage. (Over-charge, Over-discharge, max. 15A charge/discharge current, short circuit, etc.)

I will use some buck converters to make up the rest of the power bank; 2 pc. 5V, 3A dual usb ports (6,5-35V in), and a dc-dc 0.1-5A CC/CV charger (4.5-30V in, 0,8-30V out).
With that CC/CV charger, i can use a 12V battery as a charging source, or connect a solar-panel directly.
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

Bruce S

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Re: used 18650 in series and parallel - opinions.
« Reply #5 on: June 27, 2017, 03:06:16 PM »
Simen;
After reading over this I'm a little curious .
Those laptop 18650s what happens if you google the part number on them?
All of the 18650s I have each come in around 2100mA. I've paralleled  them so I have about 8000mA with the voltage sitting at 4.0Vdc Then Series enough of those packs to bring it up to 14.4Vdc.
I'm just curious as to what each one of your cells ratings are.
There are 18550s that come in around 500mA those are shorter than the 18650s and I love using those in my free/cheap LED flashlights as they are a direct swap and last a tons longer than the 3 little AAAs.

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Bruce S
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george65

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Re: used 18650 in series and parallel - opinions.
« Reply #6 on: June 27, 2017, 08:34:39 PM »
There are 18550s that come in around 500mA those are shorter than the 18650s and I love using those in my free/cheap LED flashlights as they are a direct swap and last a tons longer than the 3 little AAAs.


This raises my interest!
I have 6 or more little torches that are very good apart from battery life that use AAA's and thought of using a 18650 but read they won't Fit.
Are the 18550's available still? I tried fleabay but can't find any. Were they only fitted to laptop packs?

I want to get an 18650 Torch but get bamboozled every time I look as to what is good and economical and what is just crap.

The 18650 batteries advertised on fleabay are like a lot of other things where the sellers ( knowingly) post outright lies and blatantly deceive people.  Last time I looked at Creditable ( non fleabay) sources)  it was stated the max capacity of 18650's at the time was something like 3600 Mah. There were any number  of cells being advertised at 5000 mah, 7000 mah and even some at 10000. You really don't know what the hell you are getting and could be 1000 mah in reality.

I think fleabay needs to start cracking down on this crap.  I recently bought some LED light bars. They were rated at 210W and I emailed the seller TWICE confirming this was the actual output to which they assured me it was and the light used 5W leds.
When I got the lights, the first thing I did was put them on a power meter and came up with 32W.... 1W leds.  Only 80% short, whats the problem.... which was pretty much how the seller saw it and they tried to spin doctor rubbish about equivalent to 210W output and then questioning my measurements and wanting pictures of my meter and questioning it's calibration.

I told them, I'm not playing games with you trying to distract me, pull one off your shelf and meter it yourself and see what the reading is. Still excuses and want me to pay to send them back which I am not going to do as they were misrepresented.
What I am going to do is an " unboxing" vid on my YT channel showing the light, the sellers name and the reading from the lights along with copys of their BS emails.  Probably my meager 25K subscribers will be of no consequence to them but it will at least give people a heads up to the way these slime ball sellers rip people off.

At least my Chinese Chainsaw has turned out to be a real winner with a couple of tweaks. Bought that on the recommendation of a mate and very happy with it. 

Simen

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Re: used 18650 in series and parallel - opinions.
« Reply #7 on: June 27, 2017, 11:06:14 PM »
Simen;
After reading over this I'm a little curious .
Those laptop 18650s what happens if you google the part number on them?
All of the 18650s I have each come in around 2100mA. I've paralleled  them so I have about 8000mA with the voltage sitting at 4.0Vdc Then Series enough of those packs to bring it up to 14.4Vdc.
I'm just curious as to what each one of your cells ratings are.

Most of the laptop packs i've opened lately have Sanyo cells (red wrapping) with a Light Blue ring around the + pole, which indicate 2600mA. Earlier, it was more common for me to find Sanyo cells with a Red ring (which are 2200mA).
I also got some Purple 'Panasonic CGR18650 E', rated 2550mA, and Peach(Salmon?) colored LG LGDBB31865, rated 2600mA.

All these came out of some 2P3S Lenovo laptop packs, which states 'Nom. 10.8V, 5.2Ah' (10.8V, 7.8Ah on those packs with 3P3S). (The earlier packs stated '10.8V, 4.4Ah...)

I found this spreadsheet, which makes it easier to identify all the messy markings and colors on the cells... ;)
« Last Edit: June 27, 2017, 11:40:23 PM by Simen »
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

frackers

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Re: used 18650 in series and parallel - opinions.
« Reply #8 on: June 28, 2017, 04:38:50 AM »
I've used a few 14550 which are the same size as an AA battery. You just have to remember they are well over twice the voltage!!
I've made some dummy AA cells for those items that take more then one AA so I can have a Lithium and a dummy to get me in the 3 to 4 volt ballpark.
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Bruce S

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Re: used 18650 in series and parallel - opinions.
« Reply #9 on: June 28, 2017, 07:09:41 AM »

I found this spreadsheet, which makes it easier to identify all the messy markings and colors on the cells... ;)
Thanks for the spreadsheet!! That does make the markings easier to figure out!
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Bruce S

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Re: used 18650 in series and parallel - opinions.
« Reply #10 on: June 28, 2017, 07:19:41 AM »
george65;
I'm finding mine in the newer solar lawn lights.
Knowing the BS out there I de-rate mine by 1/2 until I can prove otherwise.

Like Frackers, I recently picked up two lights at a thrift shop for 1/5th the original price. The batteries were dead and the container looked like it held AAs . I opened them up to swap only to find the batteries that looked like an AA was a 14550!
Nice little battery. I used a Harbour Freight multi-battery charger, put the little battery in it to jump start the charging and then put each one on one of those USB based chargers OperaHouse is so good at posting about.
I followed his post about the limiting and let it charge until the red and blue lights were on (indicating nearly fully charged) then put them back out in the solar lawn lights. They're still there working like a charm.

The freebie lights are the best for the 18550s , I take the center piece out slide , slide the 18550 in and give it a test .
I'll be looking out for those 14550 now to try what Frackers does for the ones that have to have the center thingy.

Hope this helps in your searching.

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Bruce S

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Re: used 18650 in series and parallel - opinions.
« Reply #11 on: June 28, 2017, 08:44:46 AM »
Simen;
Having read your posts about the batteries. Here's what I believe you have.
Each one of those batteries will actually have a de-rated charge of about 1800mA until they've gone thru a few cycles.

Knowing this I'm like the others with the max parallel , knowing 3P you're going to have an easy 6000mA which is way more than enough for me  8) while it's sitting at 4Vdc.
If you're looking to build something that resembles a lead acid battery then a 3S3P might be a good start. I use the in-line mini-blade Auto fuses along with water proof holder (don't want spilled coffee ruining my hard work  ;D )

This is what I use for single room LED lighting , it's recharged via HF 15watt panel I found out in the recycle bid.

Cheers
Bruce S
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Simen

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Re: used 18650 in series and parallel - opinions.
« Reply #12 on: June 28, 2017, 10:59:14 AM »
As i stated earlier, they're at 2100-2250mA already after a initial charge, then a full discharge to 3.2V and then up to 4.20 again. I'm using an 'iCharger 1010B+', which have its own test-cycle program. I'm guessing they'll end up around 2400mA after a few cycles - but time will tell... ;)

I am not building a 12V battery (for that, i use LiFePO4), but a 5V USB power bank with 4 ports and a total of 6A available on those ports. 2S6P with these cells should give me over 20Ah at 5V.

I'll post pictures in a couple of weeks. :) (Waiting for parts from china...)
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

Bruce S

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Re: used 18650 in series and parallel - opinions.
« Reply #13 on: June 28, 2017, 12:59:46 PM »
Sorry about that , should've re-read the 1st posts :-)
I'll be interested to see how that looks!
What will you be using to charge it back up?

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 Bruce S
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Simen

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Re: used 18650 in series and parallel - opinions.
« Reply #14 on: June 28, 2017, 02:01:16 PM »
I'll use this one; setting it at 3A charging current will charge the pack in 4-5 hours, and i can use whatever power source within 10-30V that is available...
I've ordered two, so i'm considering using both... :)
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

Simen

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Re: used 18650 in series and parallel - opinions.
« Reply #15 on: July 16, 2017, 04:35:43 AM »
I've received all the parts; mishandled a piece of 4 mm plywood, and put it all together. :P

10627-0

And the innards;

10628-1

Everything performs just as i hoped. ;) The voltages out from the usb ports are reasonable stable; at around 5.17V unloaded, and it drops to around 5.13V with 1A load. (I haven't testet with larger loads yet.)

The battery graph/display should be calibrated for 2S LiCo cells, with 100% at 4.20V, and 0% at 2.95V.

I've adjusted the charger to 8.32V (4.16V/cell), and a constant-current of 3.0A, and i've set the charge-light to switch from red to green at 200mA draw, indicating end-of-charge.

10629-2

I'm using Anderson PowerPole connectors for connecting a charge-source, since i already use them on my many smaller (10-100W) loose solar-panels.
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

dnix71

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Re: used 18650 in series and parallel - opinions.
« Reply #16 on: July 16, 2017, 08:45:00 AM »
Simen if you drop the voltage from 4.16 to 4.0 you will get many more cycle out of the cells. At 4.16 and above lithium metal begins to plate out inside the cells and that is what reduces their life.

I have dozens of 14500 lithium iron phosphate cells. I use them in microphones that came with AA NiMH or alkaline cells. One lithium and one dummy cell. The real capacity is about 400 to 600mah for a 14500 cell. They can be destroyed by overcharging, but I have never seen one burn even though the plastic label melted off and the cell got hot enough to set paper on fire. Those were installed in a cordless drill in place of the original NiCads. I had to buy a special charger from eBay for about $10 to charge the pack correctly, but that works perfectly and the cells stay charged for months sitting in the tool cabinet.

I am only guessing, but an 18650 would probably hold 1000 mah in real life, no matter what some eBay seller say.
I wish there was some way to hold eBay executives personally accountable for allowing blatant liars to sell batteries with fake capacities.

Simen

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Re: used 18650 in series and parallel - opinions.
« Reply #17 on: July 16, 2017, 09:06:40 AM »
Quote
I am only guessing, but an 18650 would probably hold 1000 mah in real life, no matter what some eBay seller say.

If this is your experience - stay off ebay! :D

I've never experienced a Lithium cell that has not been close to, or at, specified capacity - But then, i get them from 'respectable' laptop brands... :)

LiFePO4 cells are an another world, when it comes to safety... LiCo etc. have a runaway temp. at 140 Deg.C. ,while LiFe are around 260 Deg.C.; much safer.

BTW: How did you manage to get LiFe cells that hot?!?! Did you charge them at 4.2V?!
They should be charged at 3.65V max...
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

Bruce S

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Re: used 18650 in series and parallel - opinions.
« Reply #18 on: July 16, 2017, 09:41:25 AM »
Simen;
I agree, all of the 18650s I've re-purposed from laptop batt-packs, they are either dead or pretty close to their rated levels.
I'm looking at a battery balance setup ($110USD) so I can actually test to batteries before assembling the packs.

I helped a friend swap out one of the modules in his Hybrid Camry, the unit he bought worked so well for find the bad module and testing my packs I'm ordering my own.

I don't have enough of the 145xx to say, but the ones out in my solar lights last a long time.

PS>>> I order any batteries I have to have from aliexpress. I'm in no real hurry so them taking 7-10 days is no big deal
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dnix71

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Re: used 18650 in series and parallel - opinions.
« Reply #19 on: July 16, 2017, 10:34:21 AM »
Simen I burned up some 14500 LIFePO4 cells by using an unregulated charger iintended for NiCads. They took a remarkable amount of abuse before failing.

I am very choosy about buying rechargable cells of eBay. There is a Battery Store in town again. I can get almost anything there but the price is high. NiMH cells are also overrated on eBay. I stick with Duracell brand and have not been disappointed yet.