4 ms·

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

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.
  - mschuster91 2y ago
    > That being said who knows how bad these cells are. I think there's a reason these things are disposable in the first place... only God knows where the f..k the original fly-by-night producer of these vapes sourced them from, or what kind of quality control has been done on them. Or who skipped on a fraction of a cent per piece on a million batteries...

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.
- mschuster91 2y ago
  > That being said who knows how bad these cells are. I think there's a reason these things are disposable in the first place... only God knows where the f..k the original fly-by-night producer of these vapes sourced them from, or what kind of quality control has been done on them. Or who skipped on a fraction of a cent per piece on a million batteries...