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In this project I will show you how to combine common 18650 Li-Ion batteries in order to create a battery pack that features a higher voltage, a bigger capacity and most importantly useful safety measures. These can prevent an overcharge, overdischarge and even a short circuit of the batteries. Let's get started!

Step 1: Watch the Video!

The video gives you all the information you need to make your own Li-Ion battery pack. In the next steps though, I will present you additional, helpful information.

Step 2: Order the Parts!

Here you can find a parts list with example sellers for your convenience.

Ebay:

6x INR18650-25R Li-Ion Battery (USA): http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

6x INR18650-25R Li-Ion Battery (Germany): http://rover.ebay.com/rover/1/707-53477-19255-0/1?...

6x 18650 Spacer: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

Nickel Ribbon (5mm, 0.15mm): http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x XT60 Connector: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 3S Balance Connector: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

1x 3S BMS: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

Kapton Tape: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

16 AWG Wire: http://rover.ebay.com/rover/1/711-53200-19255-0/1?...

Amazon.com:

6x INR18650-25R Li-Ion Battery:http://amzn.to/2lbWame

6x 18650 Spacer: http://amzn.to/2kC5x24

Nickel Ribbon (8mm, 0.15mm): http://amzn.to/2l7rB5t

1x XT60 Connector: http://amzn.to/2lbQCbu

1x 3S Balance Connector: http://amzn.to/2kGDDBC

1x 3S BMS: http://amzn.to/2jPbNUE

Kapton Tape: http://amzn.to/2lbKcJp

16 AWG Wire: http://amzn.to/2lbPuVt

Amazon.de:

6x INR18650-25R Li-Ion Battery: http://amzn.to/2lbEhUE

6x 18650 Spacer: http://amzn.to/2lc3e2A

Nickel Ribbon (8mm, 0.1mm): http://amzn.to/2lbP2Gv

1x XT60 Connector: http://amzn.to/2lbVsGx

1x 3S Balance Connector: http://amzn.to/2lc1O89

1x 3S BMS: http://amzn.to/2lc3FtK

Kapton Tape: http://amzn.to/2lbVxu2

16 AWG Wire: http://amzn.to/2lbXd5S

Step 3: Do the Wiring!

Now that you have all the required components, it is time to do the wiring. You can use the pictures of my finished battery pack and the scheme from the video as a reference.

Step 4: 3D Print the Enclosure!

Here you can find the 123D file and the stl file of my design which you can use to 3D print your own enclosure.

Step 5: Success!

You did it! You just made your own Li-Ion Battery Pack!


Feel free to check out my YouTube channel for more awesome projects:

http://www.youtube.com/user/greatscottlab

You can also follow me on Facebook, Twitter and Google+ for news about upcoming projects and behind the scenes information:

https://twitter.com/GreatScottLab

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<p>Wow. I can't believe Instructables would feature a project where someone recommends soldering directly to 18650 terminals. </p>
<p>Why is that dangerous (im kimda a noob and have no idea why)</p>
Applying that much heat directly to a terminal of a high-discharge battery is always a terrible idea. Besides damaging the battery, you could also have it explode on you.
<p>it is True ?</p>
<p>An alternative to soldering to 18650 terminals is soldering to 18650 holders that come with PCB mounts. I prefer balance charging them in a holder because it's convenient and doesn't damage their labels. This is good for high powered bike lights!</p>
<p>One of the smaller packs i make, this one for a headlight. Please be aware of the many flaws in this tutorial which can not just ruin your projcet but also catch fire or kills you.</p>
<p>great video, thank you! </p>
<p>I always enjoy your Great Scott videos. Very informative, well thought out and neatly executed. I concur about the difficulty of making a spot-welder and using solder instead. As long as careful steps are taken to avoid overheating the cells, soldering works as well or better than spot-welding. I wonder, however, why you included a BMS when you're already using a balance charger? I made a similar instructable recently for an e-bike battery pack that included a balance charger but no BMS because there was no room for one: https://www.instructables.com/id/How-to-Rebuild-a-BionX-E-Bike-Battery-Pack/ </p>
<p>Thanks Greatscott this is an awesome post!</p><p>Correct me if i'm wrong but the cells can be balanced by charging them in all at the same time in a 1S1P configuration with a BMS for that until they are full</p><p>If you can easily detach the batteries this is possible. like I can because I bought a holder like they have in RC cars for the cells and did the same wiring as on this post.</p><p>Also a perk of this methode is you don't have to risk the batteries exploding on you. and easily replace &quot;bad&quot; batteries.</p><p>Make sure though that the batteries are in good contact with the contacts and that they are well attached so they don't go lose.</p><p>I will only take out the batteries when I really need to.</p><p>- Maarten</p>
<p>can this battery be used for drones ? as I saw you compared it with lipo and lipo is usually recommened for drones... if yes than what would be the advantages or disadvanteges of this battery over lipo. ?<br></p><p>Great project as always btw....</p>
<p>yes and are better</p>
way too heavy
<p>Think long and hard before soldering a battery terminal - my brother lost his eye that way!</p>
<p>Fantastic, I was looking at making something similar and this will give me great grounding to make a Li-Ion battery myself. Forgive me, I don't mean to disrespect this or your work I really appreciate the effort, time and work you have put into this. I will make it to your specifications and plans - I am just one that always looks to improve and take something to the next step, and for that I may fail! But having said all that, great work and I shall report to you how I got on and just end with a note of great thanks and keep up the good work! </p>
What is the discharge rate of the battery pack?
<p>The peak current is 40A if you would not use a BMS. </p>
<p>This seems just right for my recumbent trike. 'Bents can use a silly number of lights for visibility. Thank you!</p>
<p>This arrangement is same as most laptop packs, so why go thru all the expense and just get a laptop pack - leave on the BMS it has and add your XT60 connector. All cells in the laptop battery are already spot welded as 3S2P. </p>
<p>Hello! Some brief comments:</p><p>Rajones4 warned against subjecting cells to undue thermal stress, good advice fellows. &iquest;Sonic welded? WTF? Maybe you meant &ldquo;spot welded&rdquo;, Rajones4. That's the industry standard practice.</p><p>There are other ways to interconnect batteries. One which I've succesfully used is to attach copper sheet/flattened wires over the terminals with disk shaped neodymium magnets, and affix the stuff with hot glue. If going high current, copper sheet and thick neodymium magnets are advised (higher permeance coefficient and operational temperature, magnet wise). Other possibility is to solder with low temp solders like Rose's Metal (94-98&deg;C), Bi55.5Pb44.5 (maybe a tad high at 124&deg;C), etc.</p><p>Cheers</p>
<p>What is better round (like the 186540) or flat cells? I am looking for <br>is single cell with a very high discharge (20c or 40C needed to fire ematches in a high power rocketry project) with <br>protection and rated atleast 2000mAH (4000 would be nice). What cell <br>would you recommended?</p>
Hi, nice project!<br>How does the BMS protects all the cells if it's a 3S and you have 6 cells? Ain't you afraid of unbalanced pairs?<br>Thanks.
<p>Unbalanced pairs? LoL!</p><p>If properly connected, cells in parallel ALWAYS stay balanced. In nearly all of the respects which matter here, they're pretty much equivalent to a single larger cell, with a better surface/volume ratio and thus cooling ability.</p>
Hey Barkuti,<br>No offense here, just read that thread, this is a real deal, no LoLs:<br>http://electronics.stackexchange.com/questions/126673/charging-li-ion-batteries-in-parallel<br>Thanks.
<p>ensuring balanced parallel pairs is done from the beginning- it isn't industry standard to monitor every parallel cell. The thing is, every cell is going to be sliiiiightly different than the cells next to it coming off of the assembly line. If they're coming from the same batch from the same manufacturing run, they're going to be (nearly) indistinguishable, and identical-enough to not create problems with differences in capacitance.</p><p>The issue that you're describing usually arrives when someone builds a pack with leftover/recycled laptop cells, or generic/poorly-manufactured/&quot;bargain&quot; cells. The tiny (or more) variances in capacitance from cell to cell, once added up, can become glaring. The pack's usable capacitance is then limited to the smallest parallel string's capacitance- it can't be fixed with active electronics because the differences in capacitance are caused by manufacturing differences &amp; chemical wear within the cell.</p><p>Even if you're not stacking multiple cells in parallel, you should use the same manufacturer (and ideally the same batch) when stacking single cells in series. a cell with a large capacitance will still be limited by the capacitance of a smaller cell in series with it (Barkuti is right about multiple cells behaving like one larger cell)</p>
<p>I was wondering the same thing.</p>
<p>OMG!! Soldering on Li-Ion cells! Overheated cells go POOF, big time. Great <br>if you are trying to earn a new nick-name like &quot;Patch&quot; or &quot;Stumpy&quot;. Be <br>smart; buy cells with tabs already welded on.</p>
<p>Important safety note for anyone planning on building this:</p><p>Li-Ion cell terminals are only meant to be sonic welded- they should never be soldered. You can buy cells with solderable tabs already sonic welded to the cell terminals, but the terminals themselves should never be soldered directly to the wire; doing so can (and likely will) lead to cell-by-cell capacitance disparity (which can't be fixed by balancing because you now essentially have multiple cell capacitances), or worse- unscheduled rapid thermal disassembly (fiery explosion) - which can happen either during the solder process or while the pack is being charged/discharged during regular use.</p><p>Please stay safe. A soldering iron should never touch a battery terminal, ever.</p>
<p>Thanks. That is good to know. You rock. </p>
<p>verry nice and usefull thanks</p>

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