i shit you not. i was LITERALLY just designing my own battery pack for use on a long range drone and thought to myself "if only bardwell had a video on it". perfect timing
As long as you respect and understand the risks you are committing to, it can be a fun challenge. Please use PPE and take every precaution you can think of to avoid short circuits as illustrated. I go a step further and use kapton tape as I build the pack in case a nickel strip moves, etc.
@@silverstoned83 Yup I got it done. I remember when I made my first pack following a guide on UA-cam I did a 12v pack 2 in series 6 cells and blew up whatever I plugged it into puff of smoke came out because there were too much amps going through it make sure you match the amperage to what ever the device can tolerate 12v/14v 2000mah I put 12v 4000mah.
When you make parallel groups, use a longer strip, so it hangs off the end, allowing you to solder your balance leads and mains to a strip, instead of on the tops of the cells. Also for a goggle pack I always recommend Panasonic NCR18650B in 2S or 3S 1P. You'll get 3,400mah 10Amp discharge, works excellent for goggle packs and small enough to fit in a pocket or on headstrong. I always carry 2 of these, rarely need the backup. Also, if you're going g to do 2P packs instead of standard strips, you should get "railroad tracks" that are double wide strips and each cell can flow to the next. That also helps when using an underpowered welder, because you don't have to stack strips. Another pro-tip is to put foam over your welds before you tape it up/or wrap it, to protect them from normal use 👌
My inner pedant wanted to jump in and correct you to say "its soldering" and then I remembered he is literally using a spot welder and not soldering the cells together at all😂
One good thing to do… use masking tape while working on each section. Helps if you accidentally drop a strip or something fumbling around where it could fall and short a set. I tape each before and then tape again each section when I’m done.
I have been building li-ion battery packs for almost 5 years now. In that time I started up a small side business building custom batteries for super long endurance drones/rc planes, developed a battery packs for electric ultralight aircrafts, and am now the battery design/construction team lead for an electric racecar team. Here are my tips for anyone who wants to build a pack: -Find and compare third party testing for the cells you are looking at -NEVER solder directly to cells -Especially on larger packs, design the battery to give significantly more current than its theoretical capability. Heat can build up quick and it will significantly improve both efficiency and the life of your battery.
Seems like you have a lot of knowledge on this subject. I recently got a *decent* spot welder to make packs but I see people talking about soldering 14 gauge wire directly to batteries for more current. What would you say the minimum width/thickness pure nickel strips should be when spot welding a pack for fpv use to carry enough current? .15 is available everywhere and .2 is def less common but possible to get. Curious what you'd use for say a 6S battery?
Made 4 batteries and solder them all, obviously taking precautions and the main one was to have a stainless steel flux, the time contact of the tip the the battery was less than couple seconds each time
@dan.learns.things If I were in your situation, I would do triple layers of 10mm x 0.15mm nickle. That will give you 30 amps continuous, and I have pulled 90amp bursts through it.
Use Battery Cell Spacers ! i dont like to glue cells together, i mostly use 3d printed chell holders for seperation. the insulation of those cells is sometimes realy weak and its the only thing where the glue binds to and that holds the pack shape . if dropped it can easily rip off the insulation of the cells(and you know what happens than). i assume you have a 3d printer, so just use it to print some spacers. also those spacers make it way easyer to hold the cells in shape while working, and they are easy and fast to print and just realy good. also some work like the fishpaper things and you dont need it as an extra part.
Correct, print cell holders. They can be designed like a grid in any configuration you want to build. They're safer, and the frame can take hits. TPU works great. The openings are slightly smaller than the cell itself, making for a snug fit. Then shrink wrap around it all.
Ver good! I agree with everything you say! Constructed and build many packs, also for cars, ebikes etc. Only one word of criticism maybe: I wouldn’t use TPU for the cell holders: why? Because your cell holders offer the great advantage of stiffness to the construction. When there’s torsion force to the pack (due to falling, vibrations, in a backpack you name it) and the holders are made of flexible material such as TPU what will have to take the load? It’s the nickel strips. And after time the spot welds may come loose, cracks will form through the material etc. That’s the only big disadvantage about that material in that specific usecase! 😀
@@sioul2006 In this case im not spot welding the leads. I'm soldering the leads with a slight arc. So the cells can take some twisting. The shrink wrap is also contributing to the stiffness. This for quads and planes. In an rc car howewer it's probably as you say safer to use rigid material as it will bounce around much more. Happy new year!
@@icp-trek happy new year! 😄 How are you soldering them without putting too much heat into the cell? Anything heating the cell up more than spot welding shouldn’t be done
I built an 18650 pack out of batheries from an old drill thinking it was going to be complete ass, and while battery sag is a bit of an issue, i can still get 10-12 min flights out of it. Cant beat that!
“ca accelerator” is just Sodium bicarbonate. aka baking soda diluted in distilled water. so you can make your own very cheap. or just sprinkle baking soda, the CA does get hot though.
I used to use a home made track and would charge 18650 with a isdt charger to get internal resistance. Now isdt makes an 18650 charger that shows internal resistance. I love it
@Joshua Bardwell !!!PSA!!! Just a word of caution to you and whoever else reads this, the spot welds that you made appear to be almost blowing through the cells... It's hard to say for sure in the video but in my opinion you have the power setting turned up too high. I've done it many times myself when I first started. If the power is turned up too much the spot weld will actually go all the way through the metal on the cell which on the bottom of the cell can cause it to leak / vent over time! The top of the cell is not so much the issue as the bottom. On the top of the cell there's a gap between the top of the cell and the internals. But on the bottom of the cell if the spot weld pierces through that surface metal it's a direct hole into the internals of the battery. Again it's hard to tell but it looks like they're too strong. I normally lean on the side of caution and turn down the power so it still produces good spot welds and just put more of them. A lot of times when I spot weld onto a battery I'll do like six or eight spot welds on each side. Anyone else reading this though just keep that in mind.
Definitely up a bit too high, not terrible though. I usually set my welder to about 30 J for a 1.2mm strip. I'm sure there's a good reference chart out there 🤙
On one of the cells there was a nick in the wrap exposing the outside negative of the battery. As soon as this happens you need to replace the wrap. I always double wrap my cells as they don't need to go inside anything like a vape so the thickness has no adverse effect.
Thank you for being willing to subject yourself to the brutal feedback of UA-cam! 🙂 One thought…when soldering on the red main POS lead the big problem is melting down through the wrap and plastic insulating ring when soldering (around 35:15 in the video). That would result in a short circuit. It might happen right away, it might happen in year after enough movement has pushed through the tiny bit of remaining plastic. A couple layers of fishpaper under any soldering points is critical IMO, even if you solder on the main lead before spot-welding..which is mandatory IMO.
Low current packs are fine like this, but it is good practice to lay series connections first one. You do gain resistance stacking strips and you want as little resistance in the series connections rather than the parallel groups because they take the full current.
FYI, the IR meter recommended here can be purchased on AliExpress for a whole lot less. I got mine recently for 36$. Model YR1035+ with all the attachments. It can also be used as a very accurate resistance meter, down to 1/100 of a mOhm. Note that it measures AC IR at 1 kHz. Not to be compared directly with DC IR. But that’s a good thing for several reasons, one of which being that cylindrical batteries’ data sheets specify the same IR @ 1 kHz.
A humble experience of learning together ❤. Also, thank you very much for your reddit reply the other day. Really helped me out in /fpv and solved all my issues. The simple things always elude me.
Actually I just wanted to say thank you because I was always curious about the balance leads. I wasn’t sure where they went, and why there was always one more wire than there are cells, but now I know.
Before you run any leads over the top of the cells you should cover the top of them (all of them) with fish tape. It just stops the nickel strip rubbing through the insulation or if youre using pvc insulation itll stop it shorting out if the wire gets a bit warm and squishy.
When I build packs I start with the shortest balance lead run and use excess wire to help extend to those longer runs. It mean another soldiering connection between wires and heat shrinking connections but its what I came up with to have a reasonable length on the balance lead
I recommend goop for glueing the cells easy to work with, less mess. good hold. Also for this low current application it makes the build easier and puts the pos / neg connections on the same end of the pack if you did + + - - and - - + + and laid out in the same 2x4 layout. the strips layout cleaner too. When you do run a wire the length of the battery I try to tape an an insulator between the wire and the strips too. For flight packs I like to have at least 2 current paths from each cell and layout closer to how you did. Not sure if proper, but it's how i do 'em!
Thanks JB for making this video! I've built a few 6S flight packs but I soldered them. I'd like to build a few more, (maybe 8S2P packs) but I wasn't sure how to build a 2P pack, and I'd also like to spot weld them, but wasn't sure how that worked either. This was great man! Thanks! Please let us know if you have any issues with the welds or the pack in the future.
@JB you can pack 4s2p assembly at other way. Main - at bottom ++-- Main + at bottom --++ At this order off cells you wield 4 cell by one long nickel stripe. And after wield on othe side it - with - , + with + , and after you make two half you just wield it together. In this method your main connection have same length. Because it located on same side off assembly. And you can easily pass balancing wire at center because you have only one cross connection on opposite side of main terminals. Think about it.
JB has me out here looking to buy massive battery banks for travel use. When the Army me issued solar blankets and battery banks I was stoke because I didn’t have to pay for but now everything is paid for by me I have to find best value for every nickel and dime I spend.
When I make batterypacks I like to make my nickelstrips longer so I can get solder tabs and dont heat the battery or melt plastic like you might end up doing with the method in the video. Also there are cheap spotwelders for less then $30 that can work with 0,1mm nickelstrips and for 18650 that will be enough if it is wide enough.
Have you thought about soldering before welding? That would avoid the heat on the cells, but it would be a little bit more tricky to welder the strips.
Thank you JB for the video. Besides the balance leads that should be protected better, it's a good idea to cut the ends of the nickel strips round at the positive cell terminals
I built my 4s 21700 lion pack today and then the movie was published :D I had to solder the cells but was careful not to touch the cells too long with the soldering iron
Another reason why you should not glue your batteries but use spacers is the fact that under the plastic cover, the metal body of the cell is used as the ground potential, meaning if the plastic accidentally rips off it can create a short circuit and that won't be good...(Applies to both 18650 and 21700)
I always used a soldering iron for my rc stuff(uav's,boats,cars), those battery packs are still going strong (even with high abuse). Now I'm building a e-bike bat and decided to use spot welder. Bought a cheap welder from ali that could be modified to make it more reliable. But maybe it's better to invest in a kWeld that can weld copper nickel sandwiches.
Nice video. I like the super glue idea (I am using small pieces of double-sided tape. You can cut the corners of the plates that go on the positive end. That way you don't risk the edge bending down, touching the negative part - learned this tip the hard way 💥 You can also cut the fish paper so the paper in between from the sheet goes between the cells as some heat protection for the soldering.
Spotwelding copper is an art! Since spot welding really is resistance welding and copper has too little resistance for mit spot welders to heat it up enough
This, the end. By far the best spot welder. Made in Germany too, if memory serves. I’ve used mine to build several packs and it can handle any thickness, no joke!
Looks like the spot welder unit I bought. Open it up, tin the lines more or strengthen by other means. Replace the battery with better quality, i used a hard case one. I can easily do 1.5 now and even 2 without issue. Also, inside you can change a connection to use a foot pedal too which I recommend.
Nice tutorial and explanation, as always by @Joshua I would just add something to be on the more safe way to not damage your batteries: You can pre-cut all the nickel strip you need for all the connection and solder the wires BEFORE spot welding them to the cells. Doing that you can put as much temperature you want (dont burn yourself please) on the strip, and even round-up the corners of the strips, those things can be sharp with strip thinner than 0.15mm. After doing all this, simply spot-weld them were they need to be and your battery will not have seen ANY temperature or risks of shorts with tweezers, solder tips, solder wire etc...
I may be wrong, but what i have done on those occasions where i must solder on a cell, i put them in the fridge for an hour to chill them, then quickly solder on them, so the majority of the cell remains cool.
1) hot glue is great in case you make a mistake its easy to separate BUT 2) i recommend rounding off the edges of your nickle strip for the positive side at least. if those edges one day pierce the outer ring its a short.
Fishpaper or cell holders are not really optional in my opinion. Especially on something has enough room and that is going to get used and abused. If you look at *9:17* there is already a cell whose wrapper is partially torn and ready to short out with the positive terminal of an adjacent cell. At lot of these glues work really well. Almost too good and sometimes are quite good at tearing cell wrappers further.
realy thin ice there soldering above the negative terminal on the positive side , you sayd it for the spotweld but forgot about it for the heat and the solder that is conductive as wel ;)
Search "portable DIY spot welder" and it's a red box looking thing. 30$ gets you a perfect spot welder for building packs (at least in my experience). Has an automatic mode and works off a 3s 5000mah lipo. Excellent bang for the buck!
You can also find pre-cut nickel strips for various battery configurations with tabs for balance leads. They've made building these easier for me. Ok I'm done now lol.
For high current draw applications like I use for my 747, (4 engine EDF) it may be a good idea to solder thicker connections with a 12awg stranded wire and use the 40A rated discharge cells. Ions are so awesome for around 40% longer run times! Gettin near 20 min flights Homiez!
I like to cut small pieces of nickel and pre-solder the wires to it, then spit weld the small nickel to where it should be connected - that way I get nice flown joints but don't have to worry about heat on the batteries
So the reason why it is generally advised to form parallel groups before series connections is due to the fact that each cell is chemically different, when connecting 2 or more cells in parallel some may have a higher voltage than others and will try to charge each other and balance the voltage, reason which thus is done before series is a higher voltage and non-limited current flow can cause the cells to have a very high watt flow and heat up, stress out and blow up...
Check your fish paper Bardwell, it should match the diameter of the cell in order for it to provide short circuit protection. Your fish paper is not large enough in diameter, which is preventing it from reaching the edge of the cell where the negative side is located, so zero additional protection is being provided. This is a critical step when building packs due to the heat that can be generated on the nickel strips, depending on the amp draw and nickel strip thickness and number of layers. The heat from the current passing through the nickel strips can become so great that the heat shrink melts away and this is the scenario that this fish paper needs to protect against.
WauW Mr. Bardwell, (happy holidays) that there looked good. I'd like to do that some day (now I probably will)! Getting a decent spotwelder next ;) As always, thanks for sharing frienD (❤)
I am a big fan of your channel. Learned a lot from your videos and thank you so much for all the effort. Could you make a video on hooking up the lastest version of mission Planner with xplane 11 and 12? Simulation SITL feature worked great in the previous versions but the lastest version of MP is a pain in the neck to set up. Thank you in advance and have a great day.
5:15 - TLDR it doesn't matter which cell you go for as both are cylindrical and will achieve a similar packing efficiency. What most people would choose is what is the most affordable to build taking into account the Price / mAh and also the type of BMS that will be required and it's cost.
I just came here to see what sort of spot welder you have :) However that CA glue is exactly what I need right now! I was wondering if there were any with a long tip like that to put the glue in more precisely.
Left off in 2020 flying an Xclass on 6s4p with over 20 minutes of flight time on 11600mah cruising at 50mph. Was a little under powered, 8s4p would have been ideal. The 20inch monster I was gonna build wpuld have been 6s8p. Best general performance I had was 6s2p 10 inch with 3115 980kv motors, good thrust and endurance.
I have just built a couple of batteries myself and I am a worse DIYer than you are, but for the XT60 soldering part. I have elongated the two nickel strips at the end of my batteries so that I can solder "outside" of the batteries and not be so afraid of heating too much when doing the solder job. I have also found that to be a nice thing as I can bend the strip aroung the edge and get a little bit longer of a XT60 wire (I have stopped building my own after having to rebuild a quad due to powerloss).
i have a few safety issues with your design;) In the Video 35:00, where you are soldering, only the shrinktube from the cell is protecting you from a short circuit with the negative side of the cell. there are insulation stickers available to give you a better protection. Use Cell holders, so you have more safety distance between the cells in case of a crash or drop. also here only 2 layers of thin shrinktube is protecting here from a short circuit between the positive side of the cell and the negative side. In my opinion 0.15mm is too less by far. with that width it should not go over 7 Amps to stay cool, there are enough charts online to check what amperage it can handle.
I built a 6s molicell 21700 45a and worth every minute spent building it because the red lithium versions of this are the same exact specs as the one I built but yet they range from $130 to $189 depending where you buy it at and I got all six of mine with shipping for $40
dont wrap upper and lower sides directly with kapton, put fishpaper on them first, under high exigence the nickel strips will heat a lot, even melting the kapton and doing a short, the fish paper would prevent it, it happend to me a few times when i crashed the drone, broke the proppellers and it started RTH full throotle till i arrived.
Should the connections across not be made in a square across both cells rather than only across on one side. Square each end and square opposite side in middle??
Your stuff is always good and even the things where I think you could have done better is educational in that I’ll try to not make the same mistakes. I’ll drop an extra $50 or so on my welder and make sure that I get longer balance lead harnesses. thanx.
I would have put capton tape down first so the balance wires couldn’t rub on the cells any where. And definitely do custom harness for your balance wires a short lead will lead to stress on the wires 🤣🤣
@@Honeythebeebee that makes more sense, however probably more a 60A pack with the P50Bs rated at 60A max continuous discharge. Easy mistake to make, even in this video at 2:40 the GEPRC pack says 15C/30C, which is incorrect and probably meant 15A/30A since the Sony VTC6 cells are 15A continuous or 30A max making it a 5C/10C
I wouldn't really trust a joint where the only reason solder doesn't fall off is a scratched up surface, that's replacing full surface contact with multiple small points, potentially creating hidden failures for no reason. Just use flux. Regular liquid flux works fine with nickel (both the strips and the cells).
Could you have the wires coming out the top center of the pack? means most wires will have the same distance to travel rather than some the whole pack and some only an inch or 2
Titles video “building 18650 battery pack”. Proceeds to build 21700 battery pack. 😂 never change Joshua
It's all about search and the algo, I suspect. JB is a smart man.
@CyclingMikey yeah, 18650 has become more of a general term rather than a battery size 😂
@EagleFPV43 yea people still saying 18650. But like so many things like EUC using 21700 cells now
I mean, they’re pretty much the same thing for the purposes of this video.. and 18650 would probably satisfy the algorithm better. Genius I say.
Definitely a little disingenuous, even if it is only to satisfy the inane algorithm.
i shit you not. i was LITERALLY just designing my own battery pack for use on a long range drone and thought to myself "if only bardwell had a video on it". perfect timing
fukin scary m2
eh, use 21700.... molicell p45. you'll thank me later😁
@@lolmetyuri and me
As long as you respect and understand the risks you are committing to, it can be a fun challenge. Please use PPE and take every precaution you can think of to avoid short circuits as illustrated. I go a step further and use kapton tape as I build the pack in case a nickel strip moves, etc.
@@silverstoned83 Yup I got it done. I remember when I made my first pack following a guide on UA-cam I did a 12v pack 2 in series 6 cells and blew up whatever I plugged it into puff of smoke came out because there were too much amps going through it make sure you match the amperage to what ever the device can tolerate 12v/14v 2000mah I put 12v 4000mah.
When you make parallel groups, use a longer strip, so it hangs off the end, allowing you to solder your balance leads and mains to a strip, instead of on the tops of the cells. Also for a goggle pack I always recommend Panasonic NCR18650B in 2S or 3S 1P. You'll get 3,400mah 10Amp discharge, works excellent for goggle packs and small enough to fit in a pocket or on headstrong. I always carry 2 of these, rarely need the backup. Also, if you're going g to do 2P packs instead of standard strips, you should get "railroad tracks" that are double wide strips and each cell can flow to the next. That also helps when using an underpowered welder, because you don't have to stack strips. Another pro-tip is to put foam over your welds before you tape it up/or wrap it, to protect them from normal use 👌
🤘
Great tips!
My inner pedant wanted to jump in and correct you to say "its soldering" and then I remembered he is literally using a spot welder and not soldering the cells together at all😂
@@bigdatapimp hahaha, we all love to argue 🙌
Thanks for adding these great suggestions!
One good thing to do… use masking tape while working on each section. Helps if you accidentally drop a strip or something fumbling around where it could fall and short a set. I tape each before and then tape again each section when I’m done.
Good call! That's a great safety tip.
I have been building li-ion battery packs for almost 5 years now. In that time I started up a small side business building custom batteries for super long endurance drones/rc planes, developed a battery packs for electric ultralight aircrafts, and am now the battery design/construction team lead for an electric racecar team.
Here are my tips for anyone who wants to build a pack:
-Find and compare third party testing for the cells you are looking at
-NEVER solder directly to cells
-Especially on larger packs, design the battery to give significantly more current than its theoretical capability. Heat can build up quick and it will significantly improve both efficiency and the life of your battery.
Seems like you have a lot of knowledge on this subject. I recently got a *decent* spot welder to make packs but I see people talking about soldering 14 gauge wire directly to batteries for more current. What would you say the minimum width/thickness pure nickel strips should be when spot welding a pack for fpv use to carry enough current? .15 is available everywhere and .2 is def less common but possible to get. Curious what you'd use for say a 6S battery?
What's the peak current and number of parallel cells?
Made 4 batteries and solder them all, obviously taking precautions and the main one was to have a stainless steel flux, the time contact of the tip the the battery was less than couple seconds each time
@@austinsmith9413 I'd like to make one for my Tern, so a 4s1p, probably not more than 30a. I would use Molicell batteries that can output that.
@dan.learns.things If I were in your situation, I would do triple layers of 10mm x 0.15mm nickle. That will give you 30 amps continuous, and I have pulled 90amp bursts through it.
You can always pre-solder the nickel strips where you are planning to connect your battery leads. Helps keep the heat off the cells.
He said that in the video
@@McShakyFPV If he would have actually watch it all! LOL
@@KOrnhOliO1 he already knew JB wouldn't do it lol
Use Battery Cell Spacers !
i dont like to glue cells together, i mostly use 3d printed chell holders for seperation. the insulation of those cells is sometimes realy weak and its the only thing where the glue binds to and that holds the pack shape . if dropped it can easily rip off the insulation of the cells(and you know what happens than).
i assume you have a 3d printer, so just use it to print some spacers.
also those spacers make it way easyer to hold the cells in shape while working, and they are easy and fast to print and just realy good.
also some work like the fishpaper things and you dont need it as an extra part.
Correct, print cell holders. They can be designed like a grid in any configuration you want to build. They're safer, and the frame can take hits. TPU works great. The openings are slightly smaller than the cell itself, making for a snug fit. Then shrink wrap around it all.
Ver good! I agree with everything you say! Constructed and build many packs, also for cars, ebikes etc.
Only one word of criticism maybe: I wouldn’t use TPU for the cell holders: why? Because your cell holders offer the great advantage of stiffness to the construction. When there’s torsion force to the pack (due to falling, vibrations, in a backpack you name it) and the holders are made of flexible material such as TPU what will have to take the load? It’s the nickel strips. And after time the spot welds may come loose, cracks will form through the material etc.
That’s the only big disadvantage about that material in that specific usecase! 😀
@@sioul2006 In this case im not spot welding the leads. I'm soldering the leads with a slight arc. So the cells can take some twisting. The shrink wrap is also contributing to the stiffness. This for quads and planes. In an rc car howewer it's probably as you say safer to use rigid material as it will bounce around much more. Happy new year!
@@icp-trek happy new year! 😄 How are you soldering them without putting too much heat into the cell? Anything heating the cell up more than spot welding shouldn’t be done
I built an 18650 pack out of batheries from an old drill thinking it was going to be complete ass, and while battery sag is a bit of an issue, i can still get 10-12 min flights out of it. Cant beat that!
Yup, and it only weighs 2 lbs!
I've been waiting for this video for so long. Absolute LEGEND like always Bardwell.
Put some fish paper between the cells and the wiring. Silicone insulation is soft, you don't want it rubbing on any metal.
“ca accelerator” is just Sodium bicarbonate. aka baking soda diluted in distilled water. so you can make your own very cheap. or just sprinkle baking soda, the CA does get hot though.
Cool
I used to use a home made track and would charge 18650 with a isdt charger to get internal resistance. Now isdt makes an 18650 charger that shows internal resistance. I love it
@Joshua Bardwell !!!PSA!!! Just a word of caution to you and whoever else reads this, the spot welds that you made appear to be almost blowing through the cells...
It's hard to say for sure in the video but in my opinion you have the power setting turned up too high. I've done it many times myself when I first started.
If the power is turned up too much the spot weld will actually go all the way through the metal on the cell which on the bottom of the cell can cause it to leak / vent over time!
The top of the cell is not so much the issue as the bottom. On the top of the cell there's a gap between the top of the cell and the internals. But on the bottom of the cell if the spot weld pierces through that surface metal it's a direct hole into the internals of the battery.
Again it's hard to tell but it looks like they're too strong. I normally lean on the side of caution and turn down the power so it still produces good spot welds and just put more of them. A lot of times when I spot weld onto a battery I'll do like six or eight spot welds on each side.
Anyone else reading this though just keep that in mind.
Definitely up a bit too high, not terrible though. I usually set my welder to about 30 J for a 1.2mm strip. I'm sure there's a good reference chart out there 🤙
JB is using 1.5mm strips - but how thick is the cell? I thought about 0.8mm???
i did this a while ago by watching bits and pieces of a few videos but now that Bardwell has it covered, this is good.. Thanks JB
On one of the cells there was a nick in the wrap exposing the outside negative of the battery. As soon as this happens you need to replace the wrap. I always double wrap my cells as they don't need to go inside anything like a vape so the thickness has no adverse effect.
Thank you for being willing to subject yourself to the brutal feedback of UA-cam! 🙂
One thought…when soldering on the red main POS lead the big problem is melting down through the wrap and plastic insulating ring when soldering (around 35:15 in the video). That would result in a short circuit. It might happen right away, it might happen in year after enough movement has pushed through the tiny bit of remaining plastic. A couple layers of fishpaper under any soldering points is critical IMO, even if you solder on the main lead before spot-welding..which is mandatory IMO.
Low current packs are fine like this, but it is good practice to lay series connections first one. You do gain resistance stacking strips and you want as little resistance in the series connections rather than the parallel groups because they take the full current.
FYI, the IR meter recommended here can be purchased on AliExpress for a whole lot less. I got mine recently for 36$. Model YR1035+ with all the attachments. It can also be used as a very accurate resistance meter, down to 1/100 of a mOhm.
Note that it measures AC IR at 1 kHz. Not to be compared directly with DC IR. But that’s a good thing for several reasons, one of which being that cylindrical batteries’ data sheets specify the same IR @ 1 kHz.
This is what I come here for baby!! Smashing
A humble experience of learning together ❤.
Also, thank you very much for your reddit reply the other day. Really helped me out in /fpv and solved all my issues. The simple things always elude me.
Thanks!
Actually I just wanted to say thank you because I was always curious about the balance leads. I wasn’t sure where they went, and why there was always one more wire than there are cells, but now I know.
Before you run any leads over the top of the cells you should cover the top of them (all of them) with fish tape. It just stops the nickel strip rubbing through the insulation or if youre using pvc insulation itll stop it shorting out if the wire gets a bit warm and squishy.
What is fish tape? Goggle search shows wire fishing tool to pull wire. Electrical tape?
Excellent presentation as usual. You are the man!
When I build packs I start with the shortest balance lead run and use excess wire to help extend to those longer runs. It mean another soldiering connection between wires and heat shrinking connections but its what I came up with to have a reasonable length on the balance lead
I recommend goop for glueing the cells easy to work with, less mess. good hold.
Also for this low current application it makes the build easier and puts the pos / neg connections on the same end of the pack if you did + + - - and - - + + and laid out in the same 2x4 layout. the strips layout cleaner too. When you do run a wire the length of the battery I try to tape an an insulator between the wire and the strips too.
For flight packs I like to have at least 2 current paths from each cell and layout closer to how you did.
Not sure if proper, but it's how i do 'em!
Guess who was soldering an EC5 connector onto a large LiPo and got a 200A spark? Melted a 5mm semi-circle out of my Knipex pliers. Oops.
Thank you man! I can't appreciate more the info and time you shared and saved for us.
I was waiting for the inevitable “Thats not going anywhere”. LOL Nice work and thanks
Thanks JB for making this video! I've built a few 6S flight packs but I soldered them. I'd like to build a few more, (maybe 8S2P packs) but I wasn't sure how to build a 2P pack, and I'd also like to spot weld them, but wasn't sure how that worked either. This was great man! Thanks! Please let us know if you have any issues with the welds or the pack in the future.
@JB you can pack 4s2p assembly at other way.
Main - at bottom ++--
Main + at bottom --++
At this order off cells you wield 4 cell by one long nickel stripe. And after wield on othe side it - with - , + with + , and after you make two half you just wield it together.
In this method your main connection have same length. Because it located on same side off assembly. And you can easily pass balancing wire at center because you have only one cross connection on opposite side of main terminals. Think about it.
"Watch me build an 18650 battery. Step one, order 21700s to make the battery."....lol
The old bait and switch...j/k...lol🤘🤣
JB has me out here looking to buy massive battery banks for travel use. When the Army me issued solar blankets and battery banks I was stoke because I didn’t have to pay for but now everything is paid for by me I have to find best value for every nickel and dime I spend.
I made 2 packs years ago for my DJI goggles. I love mine and they work great. Got my batteries from old laptop batteries.
You can place a sheet of wax paper under whatever you're gluing to protect your desk. The glue has a difficult time adhering to the paper.
When I make batterypacks I like to make my nickelstrips longer so I can get solder tabs and dont heat the battery or melt plastic like you might end up doing with the method in the video. Also there are cheap spotwelders for less then $30 that can work with 0,1mm nickelstrips and for 18650 that will be enough if it is wide enough.
Have you thought about soldering before welding? That would avoid the heat on the cells, but it would be a little bit more tricky to welder the strips.
I could see no issues, all good for me. All your choices were backed up with logic and reason.
Perfect timing, just got my spot welder for Christmas.
HAPPY NEW YEAR JB 🥳🎉‼️✌🏼
Thank you JB for the video. Besides the balance leads that should be protected better, it's a good idea to cut the ends of the nickel strips round at the positive cell terminals
Welder works great bro, your Pure nickel strip should be at least .2 or better .3 woohoo Keep up the great Work Brother!;-)
I built my 4s 21700 lion pack today and then the movie was published :D I had to solder the cells but was careful not to touch the cells too long with the soldering iron
Another reason why you should not glue your batteries but use spacers is the fact that under the plastic cover, the metal body of the cell is used as the ground potential, meaning if the plastic accidentally rips off it can create a short circuit and that won't be good...(Applies to both 18650 and 21700)
I always used a soldering iron for my rc stuff(uav's,boats,cars), those battery packs are still going strong (even with high abuse). Now I'm building a e-bike bat and decided to use spot welder. Bought a cheap welder from ali that could be modified to make it more reliable. But maybe it's better to invest in a kWeld that can weld copper nickel sandwiches.
Love it Joshua!
Nice video. I like the super glue idea (I am using small pieces of double-sided tape.
You can cut the corners of the plates that go on the positive end. That way you don't risk the edge bending down, touching the negative part - learned this tip the hard way 💥
You can also cut the fish paper so the paper in between from the sheet goes between the cells as some heat protection for the soldering.
Nice work Joshua
I think you should try to use copper band instead of Nickel band to improve the conductivity of the "wires".
Spotwelding copper is an art! Since spot welding really is resistance welding and copper has too little resistance for mit spot welders to heat it up enough
kWeld is a very good spot welder
This, the end. By far the best spot welder. Made in Germany too, if memory serves. I’ve used mine to build several packs and it can handle any thickness, no joke!
Looks like the spot welder unit I bought. Open it up, tin the lines more or strengthen by other means. Replace the battery with better quality, i used a hard case one. I can easily do 1.5 now and even 2 without issue. Also, inside you can change a connection to use a foot pedal too which I recommend.
Feeding that algorithm for JB
Nice tutorial and explanation, as always by @Joshua
I would just add something to be on the more safe way to not damage your batteries:
You can pre-cut all the nickel strip you need for all the connection and solder the wires BEFORE spot welding them to the cells.
Doing that you can put as much temperature you want (dont burn yourself please) on the strip, and even round-up the corners of the strips, those things can be sharp with strip thinner than 0.15mm.
After doing all this, simply spot-weld them were they need to be and your battery will not have seen ANY temperature or risks of shorts with tweezers, solder tips, solder wire etc...
I may be wrong, but what i have done on those occasions where i must solder on a cell, i put them in the fridge for an hour to chill them, then quickly solder on them, so the majority of the cell remains cool.
I just did some 18650 packs, very satisfying
1) hot glue is great in case you make a mistake its easy to separate BUT 2) i recommend rounding off the edges of your nickle strip for the positive side at least. if those edges one day pierce the outer ring its a short.
Thanks for this amazing instructional video!
Fishpaper or cell holders are not really optional in my opinion. Especially on something has enough room and that is going to get used and abused. If you look at *9:17* there is already a cell whose wrapper is partially torn and ready to short out with the positive terminal of an adjacent cell. At lot of these glues work really well. Almost too good and sometimes are quite good at tearing cell wrappers further.
WELL DONE !!!!
33:37 u can make longer strip or add extra for Leeds ;)
realy thin ice there soldering above the negative terminal on the positive side , you sayd it for the spotweld but forgot about it for the heat and the solder that is conductive as wel ;)
Yes, I'd use some extra fishpaper on those spots.
Search "portable DIY spot welder" and it's a red box looking thing. 30$ gets you a perfect spot welder for building packs (at least in my experience). Has an automatic mode and works off a 3s 5000mah lipo. Excellent bang for the buck!
You can also find pre-cut nickel strips for various battery configurations with tabs for balance leads. They've made building these easier for me. Ok I'm done now lol.
Sticky back foam can be handy to give some cushion to the corners.
For high current draw applications like I use for my 747, (4 engine EDF) it may be a good idea to solder thicker connections with a 12awg stranded wire and use the 40A rated discharge cells. Ions are so awesome for around 40% longer run times! Gettin near 20 min flights Homiez!
I like to cut small pieces of nickel and pre-solder the wires to it, then spit weld the small nickel to where it should be connected - that way I get nice flown joints but don't have to worry about heat on the batteries
So the reason why it is generally advised to form parallel groups before series connections is due to the fact that each cell is chemically different, when connecting 2 or more cells in parallel some may have a higher voltage than others and will try to charge each other and balance the voltage, reason which thus is done before series is a higher voltage and non-limited current flow can cause the cells to have a very high watt flow and heat up, stress out and blow up...
12:17
@JoshuaBardwell
Check your fish paper Bardwell, it should match the diameter of the cell in order for it to provide short circuit protection. Your fish paper is not large enough in diameter, which is preventing it from reaching the edge of the cell where the negative side is located, so zero additional protection is being provided. This is a critical step when building packs due to the heat that can be generated on the nickel strips, depending on the amp draw and nickel strip thickness and number of layers. The heat from the current passing through the nickel strips can become so great that the heat shrink melts away and this is the scenario that this fish paper needs to protect against.
Thanks for pointing that out!
Thanks for everything you do and asking for such feedback to give the community the best information. Respect.
WauW Mr. Bardwell, (happy holidays) that there looked good. I'd like to do that some day (now I probably will)! Getting a decent spotwelder next ;)
As always, thanks for sharing frienD (❤)
I am a big fan of your channel. Learned a lot from your videos and thank you so much for all the effort. Could you make a video on hooking up the lastest version of mission Planner with xplane 11 and 12? Simulation SITL feature worked great in the previous versions but the lastest version of MP is a pain in the neck to set up. Thank you in advance and have a great day.
I think you should have ran the kapton tape under the wires to keep the wire off the edge of the nickel strips
Now make two 6S 24v packs in series for a 48v Power Wheels battery pack and this is the only YT channel I ever need to visit 😂
So, a 12S pack
5:15 - TLDR it doesn't matter which cell you go for as both are cylindrical and will achieve a similar packing efficiency.
What most people would choose is what is the most affordable to build taking into account the Price / mAh and also the type of BMS that will be required and it's cost.
I was sure, Josh would say "I' m Joshua Bardwell, and I am going to learn something today." 😂
I just came here to see what sort of spot welder you have :)
However that CA glue is exactly what I need right now! I was wondering if there were any with a long tip like that to put the glue in more precisely.
Just did this other week. Need 3S2P in shape to fit tank. I used solder. Dont have spot welder
Left off in 2020 flying an Xclass on 6s4p with over 20 minutes of flight time on 11600mah cruising at 50mph. Was a little under powered, 8s4p would have been ideal. The 20inch monster I was gonna build wpuld have been 6s8p. Best general performance I had was 6s2p 10 inch with 3115 980kv motors, good thrust and endurance.
I have just built a couple of batteries myself and I am a worse DIYer than you are, but for the XT60 soldering part. I have elongated the two nickel strips at the end of my batteries so that I can solder "outside" of the batteries and not be so afraid of heating too much when doing the solder job. I have also found that to be a nice thing as I can bend the strip aroung the edge and get a little bit longer of a XT60 wire (I have stopped building my own after having to rebuild a quad due to powerloss).
i have a few safety issues with your design;)
In the Video 35:00, where you are soldering, only the shrinktube from the cell is protecting you from a short circuit with the negative side of the cell.
there are insulation stickers available to give you a better protection.
Use Cell holders, so you have more safety distance between the cells in case of a crash or drop. also here only 2 layers of thin shrinktube is protecting here from a short circuit between the positive side of the cell and the negative side.
In my opinion 0.15mm is too less by far. with that width it should not go over 7 Amps to stay cool, there are enough charts online to check what amperage it can handle.
I built a 6s molicell 21700 45a and worth every minute spent building it because the red lithium versions of this are the same exact specs as the one I built but yet they range from $130 to $189 depending where you buy it at and I got all six of mine with shipping for $40
dont wrap upper and lower sides directly with kapton, put fishpaper on them first, under high exigence the nickel strips will heat a lot, even melting the kapton and doing a short, the fish paper would prevent it, it happend to me a few times when i crashed the drone, broke the proppellers and it started RTH full throotle till i arrived.
is it a better idea to solder the cables before spot welding it to the pack ? to keep the heat out ?
You can use baking soda as an accelerant
Definitely get some cell holders for doing this or 3d print them
It's a bit of work, but a decent multimeter can measure resistance without a dedicated IR tester.
I think it's better to protect your wires with Kapton tape, especially from the nickel strips.
Now, how do you add a bms to it and ill be set.😂😅
Same in welding. Crank up the heat and haul ass. Less heat transfer.
Superglue is quite brittle.
How do you charge that battery? Did you have a choice of connections for the discharge port?
Need a tutorial on a 6s3p 18650. Can’t seem to find a good diagram that I can grasp.
What is the battery/cell checker that you used when you completed the connection with the xt60? I cant seem to find it!
Should the connections across not be made in a square across both cells rather than only across on one side. Square each end and square opposite side in middle??
Your stuff is always good and even the things where I think you could have done better is educational in that I’ll try to not make the same mistakes. I’ll drop an extra $50 or so on my welder and make sure that I get longer balance lead harnesses. thanx.
Heat shrink individual cells and shrink entire pack. Much cleaner.
I would have put capton tape down first so the balance wires couldn’t rub on the cells any where. And definitely do custom harness for your balance wires a short lead will lead to stress on the wires 🤣🤣
I just made a 6s1p 5000mAh 50A with Molicel P50B last week!
P50B is 60Amp per cell, so you have a 12C pack. Why do you think you have 50C? At 50C it would be 250amps capable per cell.
@Marty_NZ 50amp, not 60. I meant 50A
@@Honeythebeebee that makes more sense, however probably more a 60A pack with the P50Bs rated at 60A max continuous discharge. Easy mistake to make, even in this video at 2:40 the GEPRC pack says 15C/30C, which is incorrect and probably meant 15A/30A since the Sony VTC6 cells are 15A continuous or 30A max making it a 5C/10C
You could have run the wires through the pack and if you're really worried about abrasion put tape on the nickel strips
I wouldn't really trust a joint where the only reason solder doesn't fall off is a scratched up surface, that's replacing full surface contact with multiple small points, potentially creating hidden failures for no reason. Just use flux. Regular liquid flux works fine with nickel (both the strips and the cells).
21700 6s is like 150 bucks. 🤘
Make one for
Could you have the wires coming out the top center of the pack? means most wires will have the same distance to travel rather than some the whole pack and some only an inch or 2
most chargers output internal resistance while balance charging :)
Yes but that is DC internal resistance which is worse than AC internal resistance for reasons that I'm not quite sure I can explain in a comment