4 ms·

Ideally you'd want to measure actual rather than reported charging capacity. For about $15 you can get a USB load generator and a USB current monitor on AliExpr

Ideally you'd want to measure actual rather than reported charging capacity. For about $15 you can get a USB load generator and a USB current monitor on AliExpress.

dist-epoch 3y ago
How do you measure actual without risking fire.
- iudqnolq 3y ago
  By being careful? If you were otherwise going to use it without testing you're not any worse off plugging it into a test setup up to your expected load. You can step up the load gradually and keep an eye on it. I would be more worried about the cheap no-brand test gear catching fire. I wouldn't plug my 100W charger into it.
  - dist-epoch 3y ago
    My point was that if you can't test safely with zero user intervention, adding this capability to computers will just cause fire incidents.
    - lazide 3y ago
      It wouldn’t cause more fire incidents than just using the cable without testing, right? The tests would only run for a tiny period of time. Most fires come from too much current through too small conductors for too long. It takes time for heat to build up to fire causing levels. The type of time required to actually try to charge something.
rini17 3y ago
Resistance is all you need to know, actually testing the max current is not necessary. Or safe, even.
- iudqnolq 3y ago
  You're right, I mixed up USB wall bricks which can have issues like the voltage dropping.
- lsaferite 3y ago
  Not an EE, but I would hope that testing max current _would_ be safe (at least on a legit cable).
  - lazide 3y ago
    Those aren’t the cables one would be hoping to find in such a test though, correct?
    - lsaferite 3y ago
      Ah, point taken.
- lxgr 3y ago
  For the newer USB-PD modes, you also need to know the maximum safe voltage (and related construction features, such as CC pins being a bit shorter to enable a safe/spark-free connection teardown), or you risk arcing.
  - rini17 3y ago
    AFAIK all cables are de-facto rated up to 30V, as you won't save money if you make insulation even thinner. So this is non issue in practice. Plus you can't really measure breakdown voltage without destroying the cable.
    - lxgr 3y ago
      PD goes up to 48V, though. And I think one important feature is having shorter CC pins in the connector, so that the power source can shut down the high voltage to avoid arcing altogether. That seems to be a feature distinct from insulation.

Ideally you'd want to measure actual rather than reported charging capacity. For about $15 you can get a USB load generator and a USB current monitor on AliExpress.

dist-epoch 3y ago

How do you measure actual without risking fire.

iudqnolq 3y ago
By being careful? If you were otherwise going to use it without testing you're not any worse off plugging it into a test setup up to your expected load. You can step up the load gradually and keep an eye on it. I would be more worried about the cheap no-brand test gear catching fire. I wouldn't plug my 100W charger into it.
- dist-epoch 3y ago
  My point was that if you can't test safely with zero user intervention, adding this capability to computers will just cause fire incidents.
  - lazide 3y ago
    It wouldn’t cause more fire incidents than just using the cable without testing, right? The tests would only run for a tiny period of time. Most fires come from too much current through too small conductors for too long. It takes time for heat to build up to fire causing levels. The type of time required to actually try to charge something.

rini17 3y ago

Resistance is all you need to know, actually testing the max current is not necessary. Or safe, even.

iudqnolq 3y ago
You're right, I mixed up USB wall bricks which can have issues like the voltage dropping.
lsaferite 3y ago
Not an EE, but I would hope that testing max current _would_ be safe (at least on a legit cable).
- lazide 3y ago
  Those aren’t the cables one would be hoping to find in such a test though, correct?
  - lsaferite 3y ago
    Ah, point taken.
lxgr 3y ago
For the newer USB-PD modes, you also need to know the maximum safe voltage (and related construction features, such as CC pins being a bit shorter to enable a safe/spark-free connection teardown), or you risk arcing.
- rini17 3y ago
  AFAIK all cables are de-facto rated up to 30V, as you won't save money if you make insulation even thinner. So this is non issue in practice. Plus you can't really measure breakdown voltage without destroying the cable.
  - lxgr 3y ago
    PD goes up to 48V, though. And I think one important feature is having shorter CC pins in the connector, so that the power source can shut down the high voltage to avoid arcing altogether. That seems to be a feature distinct from insulation.