Thanks Lee. Keep doing the amazing work you do. Love your video style and content. Heres to a lot more battery packs :D

Well done to both of you. These kinds of projects are brilliant and the content that you provide is an invaluable resource for novices like myself to learn and take inspiration from. Thanks fellas!

I love that our community helps other to build better safer pack ! Awesome Lee Wright btw you did a really nice pack for Thomas

Eskate For Life thanks brother!

@@SlightlyDazed. absolutely, I own a company that builds batteries in the UK. We have done a few ebike batteries. You can find us at www.electricskateboarding.co.uk

Yep Nick, I get the same vibes. I have taken these safety tips to heart and have eBay open on another tab and buying the "safety stuff" as I learn what's needed. I have learnt a lot from fungi and others (not the cowboys tho ;-)

While making a spot welder from a microwave transformer 👌

like whatever

Never discharge a lipo battery! They're not capacitors and will suffer if discharged.

@@TheUniversalid yeah lipo battery are more vulnerable to overdischarge than normal 18650 sized LiCoO2 cells. And yes, I didn't mean fully discharging them, only to their cut off voltage

I never discharged my cells. It's pointless as even a 'dead' cell I removed from a laptop-battery got up to some voltage after removing the real bad twin-cell. Even though it was only at 0,8 Volt or so, an accidental short made the remaining piece of strip start to glow ánd smoke. Besides pointless, it's also incredibly time-consuming. Even a 16 cell battery will take days to discharge all the cells (if you only have one Opus BT-C3100, like me). If you get your cells from a reputable store, they will all be charged at exactly the same level and you can start working right away. When I accidentally shorted my 4S4P cell with my scalpel as I tried to remove some excess heatshrink from one of the extending strips that had to be connected to the gas gauge PCB, the cells were at storage level (all at 3,65 Volt exactly). The cells itself, Panasonic NCR18650B's, aren't exactly very beefy ones when it comes to their maximum discharge current and even though the moment of contact was very brief, the short was such a scary, loud and smoking short that I immediately stopped working: I was too tired and just didn't see it coming. It vaporized the blade at the point of contact (and this is what most likely saved me). Just don't discharge them. Especially when you start pairing cells you quickly get to a point where it doesn't really matter anymore if they are fully charged or not. I shorted an INR 18650-15L from Samsung by accident: it was still a good cell, charged at 'just' 3,8 Volt but when the remaining strip (connected to the positive terminal) accidently pierced the insulation and made a short with the negative terminal, a small spark was seen and then the metal had already welded itself stuck. The cell started heating up quickly so I ran outside and placed it there waiting for the possible things to happen. Nothing did happen except for a cell that warmed up to 70 degrees Celsius and started leaking some electrolyte. But that was just 1 strong (very low internal resistance) cell. If you pair just 4 'less good' cells, you are basically at the same level. Really, discharging is completely pointless and won't make it any safer at all.

I successfully built my first pack - it is a small 4S2P pack for a model airplane - but I am very confident that it is safe and reliable, thanks to the information I gleaned from this video. Thanks again!

extremly important for high discharge packs and (or) packs used in weather conditions (heat)

Thank you Sarah for appreciating my work. Hope you enjoy the content on this channel.

Safety is paramount Ms Davis. Speaking as an Electronics Engineer with decades of experience and knowledge, The average Man with limited knowledge is thinking only of low voltage and low current. LiOn, Lead_Acid and other types are capable of producing high current and present a danger often overlooked. Even with DC voltages, once one rises above 35 volts it starts to become dangerous, even more so at high current. I expect you will soon enough comment ask me; "what about woman?" I am waiting for that one, then you will learn something you never knew before, nor will you ever know unless I teach it to you. The reason you do not know yet is that you have been successfully manipulated and programmed to know something that is not correct.

Not only less electrically conductive but also non conductive (insulator)

Stefan Hall, why is the hot glue freaking you out?

Stefan Hall

@@brucehamil-jr396 Maybe because some (not all) hot-melt adhesives [1] melt at temperatures exceeding the cell thermal runaway temperature [2]. If using hot-melt, then the trick may be to find a glue that melts at a temperature higher than the cell max operating temperature, yet lower than the temperature where permanent cell damage takes place, taking into account temperature distribution along cell enclosure etc etc. Tell me what you think... [1] en.wikipedia.org/wiki/Hot-melt_adhesive [2] batteryuniversity.com/learn/article/types_of_lithium_ion

The hot glue bothers you but the kapton tape doesn't?

I second Stefan Hall here. When the hot glue dries overtime or collect debris, it will reach some point of reabsorption. (I'm talking out of my ass here but with relative experience). Depending on usage, it can fail in 2 years or down the road. It could also conduct a little bit in the long term. Since it is sealed off like that, it's going to be increasing its moisture absorption. Think oven. When charging the batteries, it gets warm or hot. So, I liked the idea of the video using hot glue with parallel batteries. But uh I guess the solution is to use cell holders. And if needed, just use neutral cure silicone gel instead. I mean add some spacers between serial batteries for extra safety too, ie; double insulating them from each other. Furthermore, anyone interested should look into the expensive UPS back up power supply designs. They have exceptional guarantees and warranties due to their design. A lot can be learned there too about avoiding faults.

I use those black cell holder should I still isolate cells?!

@@koshitek most holders keep a distance between cells and uses that space as an isolator

@@koshitek I also use recovered or new battery holders, but I think it is safer to use fish paper or other insulation between cells that are in opposite polar orientation. Low cost, huge safety factor.

Thanks for subscribing! Om still trying to read your name though :p

agree, was not really shown in this video but seems like the smaller bms leads was soldered ont the nickel strips, which I guess is fine if it's done before the spotwelding and cannot transfer the heat into the battery.

yeah welding is at lower temperature than soldering. especially with pulses as long as in this video

Thanks for watching as always Wally.

Now a days there are big batteries which tend to be safer when joining together so they say and here is the link. ukposts.info/have/v-deo/o4mpZG9umoyDlWw.html

Sorry for my english it's not my native language :)

Yes please. Safety first!

True. Although why would they melt? Sincere question.

@@MaximC putting out 20 amps continous sometimes packs can get pretty hot!

@@Fungineers I see. So, depending on kind of currents used - additional insulation can be a good idea. Thank you for the reply.

Crossed balancing wires are a great way to start fires, even some professionally built packs (for instance: Bosch powerpacks) suffer from this.

This is true in principle, but by then it is technically too late because that one cell has other ways of corrupting the cells next to it: thermally it will be more than happy to start a chain reaction in neighboring cells. The better way to deal with this is to ensure that you treat your cells properly, avoid under and over charging (which are the conditions that can lead to internal shorts). When in doubt about the provenance of your cells monitor them using a FLIR while charging / discharging to spot the odd one out in a larger pack, or, alternatively cell-by-cell using a spot IR meter (cheaper than FLIR, but more cumbersome to use). Having a fuse-per-battery looks like a win in all cases but it also introduces a non-trivial risk: if not detected it will cause the pack to go out of balance, which can lead to serious undervoltage while discharging or overvoltage while charging up the pack with a less-than-intelligent charger. An active balancer might be able to compensate depending on how far the pack will go out of balance but there are limits to what can be done.

Spot on lol

yeah that’s misleading

Damn. Those were the days huh lol

@@Fungineers weren't they? Back when Tamiya and Kyosho were kings of the local tracks, then there were the world titles when the rich sponsored teams turned up with Team Losi or Team Associated multi thousand dollar cars minus the radio gear, motors, batteries or assembly of the little monsters, brushed motors with 3 step forward and 2 step reverse resistor banked "speed controllers" unmatched battery packs not dumping together, aiming for 5mins runtime at best, oh, they were the days haha

Those 1200Mah SCR's, or the naughty, at the time race banned 1800mah SCE's were like tanks compared to today's volatile LiPo's, sure, nowhere near the power stored, but also didn't go thermonuclear if you shorted them for a fraction of a second which I've done and OMG to anyone who hasn't you don't want it it's fecking terrifying!

Thanks for your support. I have to be more consistent with my content :(

What for you are doing hundreds of batteries? I mean for something specific (ebikes or something), and to sell them?

@@MaximC I build power packs. 500-1000 watt power packs with DC>AC 110-120 as well as build battery packs for yard products. 40-60-80v and refurbish broken packs. One cell goes bad in these packs and the BMS often won't even push an output to power the tools. I get sent hundreds of these packs a year on top of building DC to AC power packs daily and selling them. I've seen so many 18650 Li-ion cells in my time and they are really quite bullet proof.

ooh, you're so tough with your disregard for safety, it's so cool that you think you're "lvl 99". what a profoundly irresponsible and frankly stupid attitude to promote on a video about safer battery handling.

@@johndoe528 No I am saying these cells are BULLET PROOF. The genuine, good quality cells. Not the cheap Chinese cells like UltraFire or some crap like that which claim they have 10000 mAH. Every single cell I have seen from Sanyo (including heaters), LG, Sony, etc etc are BULLET PROOF. My whole point was that they are either bullet proof, or I am extremely lucky since I disregard safety with these cells and through the hundreds of thousands I have handled, none have had a catastrophic result or caused a fire. If you knew what they were on the inside you'd understand. They have 8 built in safety features. No tough guy, just experience, luck, or just plain stupidity. Either way, they are safe.

@@johnnyboy13642 well they really are physically very strong for sure, and little shorts don't kill those, now keeping one shorted for a while is another story (as would happen with a badly made pack, that just keeps shorted, or rather, aggravates the issue with time). Not like there wasn't Teslas in fire after something hitting their bottom, and the fire is hard to put out. Also, if you're working with those batteries outside, your junk bin is outside and such, then sure you got way less problems, a battery setting itself on fire on a work desk inside your house or garage might be quite dangerous, but if it's an open area where if things go thermonuclear you can just slap it away to burn in piece on the lawn, then there's way less reasons to be afraid.

I suppose youre right. I haven't really tested it but the tape insures the pack is electrically insulated.

Yes. Welding is at a higher temperature but so much shorter that the total heat injected into the cells is a small fraction of what it would be if you soldered them. The minus pole is especially sensitive to this because the cell guts are right on the other side of that very thin can, the plus pole usually has some space and limited thermal conductivity so tolerates this better. If at all possible: do not solder onto cells.