3 ms·

EDIT: This video is full with absurdly comical levels of danger. Anyone attempting to replicate this is creating a literal time bomb. I've written it up on Mast

EDIT: This video is full with absurdly comical levels of danger. Anyone attempting to replicate this is creating a literal time bomb. I've written it up on Mastodon as well, so if anyone wants to share some PSA on how to work with batteries without making a bomb, feel free to share [1]. Important note for fellow tinkerers, nearly lost my mind at 2:22: Do not ever solder directly on, or even adjacent to, lithium batteries. Only use spot welders and crimp connections. Once you cut a wire (NEVER cut two wires at once) that leads to a battery, place a Wago clamp on it to make sure it can not short accidentally. What the guy did at 7:57 is even more inexcusable, one blob of solder misplaced and he'll short the pack. And the tiny main wire, that's NOT going to survive the 30 amps he's gonna pull at 100w out. JESUS. Take the time, install proper connectors, and solder them BEFORE the pack and the PCB are electrically hot. And also, he left about zero airway for heat to escape. At full load, the inner cells will heat up! Also, never just take random cells and place them together in a parallel connection. Always measure each individual cell's capacity, only use closely matching cells, always stay 5-10% below the cutoff voltage, and never work with charged cells, only ones with max. 10% charge - only charge cells once they are installed. And ffs keep a bucket of fine sand nearby when you work with batteries. If a battery makes signs that it is about to go kaboom (it emits smoke, swells up, or catches fire), dump the bucket of sand onto the battery/device, leave the room, close the door and call 911(US)/112(EU). [1] https://mas.to/@diebarschlampe/113143039423618086 https://mas.to/@diebarschlampe/113143039423618086

jonatron 2y ago
Alternatively, have an explosion containment pie dish ready.
- mschuster91 2y ago
  Well, at least once actual explosive goes kaboom, it's gone. A battery in runoff is a fire hazard for much longer time.
Panzer04 2y ago
You can be pretty liberal about cells in parallel, it's series that bites you. He's using a 5s arrangement, it looks like - so his 100w fast charging will only be around 5-6A, not 30A, which those wires will probably be OK with (though i would have picked something thicker myself) Wiring up random batteries into series is definitely not OK, and is perhaps what you meant to refer to. I personally don't think thermals are an issue in this particular instance. 35 cells are going to laugh at 100w charging (only 3w each). The real risk is a dodgy hidden bad cells, though ideally the BMS detects this regardless. The real question is why bother with all this effort for a monstrous power bank with shit capacity. 15000mAh is nothing for that many cells.. that's the same capacity as 4-5 brand-new lithium cells, or a 50$ powebank off amazon :/. Those vape cells must be pretty shit (probably 1500mAh power-focused cells, id guess, hence the shit capacity)
- mschuster91 2y ago
  > You can be pretty liberal about cells in parallel, it's series that bites you. Yeah but at least the BMS he uses does balancing to (hopefully) keep the series packs from going into dangerous voltage territory. A dodgy cell in a parallel pack however, there's no way a standard BMS can detect that, hence pre-install measuring and matching... of course you can go for individual cell protection as well or buy cells with built-in protection but the former is overcomplicated (and hard to get right) for a DIY project, and the latter not an option as the cells from vapes don't have a need for protection circuitry. Hence, matching is a must. > He's using a 5s arrangement, it looks like - so his 100w fast charging will only be around 5-6A, not 30A, which those wires will probably be OK with (though i would have picked something thicker myself) Fair point, but still, that's not looking remotely near the 0.5 mm² that one should use for 5-6 amps of current.
  - Panzer04 2y ago
    Cells in parallel don't really need to be matched, within reason. So long as one isn't failing it generally doesn't matter. Arguably if you mixed energy cells with power cells that can cause problems, but only if you're in a high power application, which this isn't. That being said who knows how bad these cells are.
oulipo 2y ago
That's why at Gouach we created a system to build batteries without soldering! This makes them repairable and refillable :) Take a look at https://get.gouach.com https://get.gouach.com if you're interested
- serf 2y ago
  first off : terrible advertising. second : how many times do mechanical-contact 18650s need to be attempted before it's settled universally that it's a bad idea for vehicles (like e-bikes that your advertisement mentions)? I hated the VRUZEND design too and they at least had the insight to use 18650s with overlapped bus-bars for the sake of rigidity and continuity through deformation. The design that you're using is, imo, most similar to the JAG35 pcb-over-terminal designs -- but as far as I know he doesn't bother trying to use PCBs over loose 18650s; only to interface with existing and pre-welded packs or packs with pre-welded stud interfaces, usually already fairly rigid prismatic packs [0] PCBs aren't that rigid necessarily; it's easy to imagine conditions in which batteries might drop out of the network. Even with lots of bolts and thick PCBs -- uneven thermal expansion due to a poorly made cell, for example. The kind of conditions that would fry a lot of motor controllers under load should the voltage suddenly change somewhere. No thanks. Let's stick with welding, it's now dirt-cheap to buy a battery welder and it's not nearly as irreversible as groups that sell things like this would make you believe. [0]: https://jag35.com/products/fully-assembled-12v-4s2p-1200a-lev60f-battery-lifepo4 https://jag35.com/products/fully-assembled-12v-4s2p-1200a-le...
  - oulipo 2y ago
    Thanks for your comment! We have patented a design that uses the PCB plates, you can check details at https://docs.gouach.com https://docs.gouach.com. Our batteries are passing all certifications and vibration tests, and are running on 1500 free-floating e-bikes for around 2 years without issues!

jonatron 2y ago

Alternatively, have an explosion containment pie dish ready.

mschuster91 2y ago
Well, at least once actual explosive goes kaboom, it's gone. A battery in runoff is a fire hazard for much longer time.

Panzer04 2y ago

You can be pretty liberal about cells in parallel, it's series that bites you. He's using a 5s arrangement, it looks like - so his 100w fast charging will only be around 5-6A, not 30A, which those wires will probably be OK with (though i would have picked something thicker myself) Wiring up random batteries into series is definitely not OK, and is perhaps what you meant to refer to. I personally don't think thermals are an issue in this particular instance. 35 cells are going to laugh at 100w charging (only 3w each). The real risk is a dodgy hidden bad cells, though ideally the BMS detects this regardless. The real question is why bother with all this effort for a monstrous power bank with shit capacity. 15000mAh is nothing for that many cells.. that's the same capacity as 4-5 brand-new lithium cells, or a 50$ powebank off amazon :/. Those vape cells must be pretty shit (probably 1500mAh power-focused cells, id guess, hence the shit capacity)

mschuster91 2y ago
> You can be pretty liberal about cells in parallel, it's series that bites you. Yeah but at least the BMS he uses does balancing to (hopefully) keep the series packs from going into dangerous voltage territory. A dodgy cell in a parallel pack however, there's no way a standard BMS can detect that, hence pre-install measuring and matching... of course you can go for individual cell protection as well or buy cells with built-in protection but the former is overcomplicated (and hard to get right) for a DIY project, and the latter not an option as the cells from vapes don't have a need for protection circuitry. Hence, matching is a must. > He's using a 5s arrangement, it looks like - so his 100w fast charging will only be around 5-6A, not 30A, which those wires will probably be OK with (though i would have picked something thicker myself) Fair point, but still, that's not looking remotely near the 0.5 mm² that one should use for 5-6 amps of current.
- Panzer04 2y ago
  Cells in parallel don't really need to be matched, within reason. So long as one isn't failing it generally doesn't matter. Arguably if you mixed energy cells with power cells that can cause problems, but only if you're in a high power application, which this isn't. That being said who knows how bad these cells are.

oulipo 2y ago

That's why at Gouach we created a system to build batteries without soldering! This makes them repairable and refillable :) Take a look at https://get.gouach.com https://get.gouach.com if you're interested

serf 2y ago
first off : terrible advertising. second : how many times do mechanical-contact 18650s need to be attempted before it's settled universally that it's a bad idea for vehicles (like e-bikes that your advertisement mentions)? I hated the VRUZEND design too and they at least had the insight to use 18650s with overlapped bus-bars for the sake of rigidity and continuity through deformation. The design that you're using is, imo, most similar to the JAG35 pcb-over-terminal designs -- but as far as I know he doesn't bother trying to use PCBs over loose 18650s; only to interface with existing and pre-welded packs or packs with pre-welded stud interfaces, usually already fairly rigid prismatic packs [0] PCBs aren't that rigid necessarily; it's easy to imagine conditions in which batteries might drop out of the network. Even with lots of bolts and thick PCBs -- uneven thermal expansion due to a poorly made cell, for example. The kind of conditions that would fry a lot of motor controllers under load should the voltage suddenly change somewhere. No thanks. Let's stick with welding, it's now dirt-cheap to buy a battery welder and it's not nearly as irreversible as groups that sell things like this would make you believe. [0]: https://jag35.com/products/fully-assembled-12v-4s2p-1200a-lev60f-battery-lifepo4 https://jag35.com/products/fully-assembled-12v-4s2p-1200a-le...
- oulipo 2y ago
  Thanks for your comment! We have patented a design that uses the PCB plates, you can check details at https://docs.gouach.com https://docs.gouach.com. Our batteries are passing all certifications and vibration tests, and are running on 1500 free-floating e-bikes for around 2 years without issues!