3 ms·

However there is a lot of leeway on the "48V is the highest safe voltage" statement too. 48V has a special place in regulations because of its use in telco, but

However there is a lot of leeway on the "48V is the highest safe voltage" statement too. 48V has a special place in regulations because of its use in telco, but 60V DC is still very safe.

hinkley 3y ago
Doubling again to 96 is not safe, however. I’m not sure why they settled on powers of two. Something perhaps to do with noise filtration, and fewer new tricks to learn?
- myself248 3y ago
  It's convenient to build things in multiples and powers of 2 and 3. A nice two-tier or four-tier battery rack full of 2-volt cells just works out nicely.
  - hinkley 3y ago
    Smaller transformers with whole numbers, right? But why 4 and not 3 or 6?
    - eternityforest 3y ago
      We seem to stick with 7-smooth numbers, and really extra prefer highly composite numbers (https://en.m.wikipedia.org/wiki/Highly_composite_number https://en.m.wikipedia.org/wiki/Highly_composite_number) for things we chose before the age of calculators. 3 and 6 were the standard voltages for consumer stuff back in the days of people needing to buy multiple packs of AA cells every year
      - jjeaff 3y ago
        Are we not all still buying multiple packs of AA batteries every year? Or maybe it's just those with kids.
        eternityforest 3y ago
        I think it might mostly just be those with kids! And non techies. They always have a few disposable battery flashlights hanging around it seems like.
        myself248 3y ago
        Oh I hope nobody's doing that, rechargeables have been so good for so long. I'm just now retiring some that I bought in the 2007-2011 timeframe which have started to fail, but my 2015 purchases are still going strong with hundreds and hundreds of charge cycles on 'em. I haven't used alkalines since the 80s.
        jjeaff 3y ago
        I have not had great luck with rechargeables. They have a lower voltage than regular AA, so I find that most sensitive electronics just start out thinking the battery is already low and then stop running before the battery is fully discharged. My Z-wave keypad lock is one of those. AA batteries last about 2 months, rechargeables start giving a low battery warning after a week and hardly last 2-4.
        eternityforest 3y ago
        Have you tried lithium rechargeables with the built in converters?
        myself248 3y ago
        I return garbage products like that. Not supporting rechargeables in 1980 was sort of forgivable, but they've had 40 years to get their act together.
- eternityforest 3y ago
  Aside from modern barrel jack supplies, none of it is actually powers of two, it's like, 13.8v lead acid or a little higher for lithium. I think we just stay close to the numbers we do, because we just really like multiples of 12 and numbers with lots of divisors. 24 hours in a day, 360 degrees, etc. Most numbers people really like a lot seem to be on the 7-smooth numbers(https://oeis.org/A002473 https://oeis.org/A002473) list and related/overlapping sets like highly composite numbers. Which I think is super cool, because it means you can choose one and there's a good chance someone else chose it too for something similar, unless they were using renard numbers or something instead.
- nippoo 3y ago
  A lot of 48V infrastructure comes from the marine world - where 4 x 12V lead-acid batteries in series is common for this reason. So a lot of components already exist and can be made to work in the automotive sector with simple modifications. (In the marine world, it's much simpler to combine and split batteries in powers of 2 for cell balancing - you can take 4 x 12V batteries and charge them in parallel, discharge them in series)

However there is a lot of leeway on the "48V is the highest safe voltage" statement too. 48V has a special place in regulations because of its use in telco, but 60V DC is still very safe.

hinkley 3y ago

Doubling again to 96 is not safe, however. I’m not sure why they settled on powers of two. Something perhaps to do with noise filtration, and fewer new tricks to learn?

myself248 3y ago
It's convenient to build things in multiples and powers of 2 and 3. A nice two-tier or four-tier battery rack full of 2-volt cells just works out nicely.
- hinkley 3y ago
  Smaller transformers with whole numbers, right? But why 4 and not 3 or 6?
  - eternityforest 3y ago
    We seem to stick with 7-smooth numbers, and really extra prefer highly composite numbers (https://en.m.wikipedia.org/wiki/Highly_composite_number https://en.m.wikipedia.org/wiki/Highly_composite_number) for things we chose before the age of calculators. 3 and 6 were the standard voltages for consumer stuff back in the days of people needing to buy multiple packs of AA cells every year
    - jjeaff 3y ago
      Are we not all still buying multiple packs of AA batteries every year? Or maybe it's just those with kids.
      - eternityforest 3y ago
        I think it might mostly just be those with kids! And non techies. They always have a few disposable battery flashlights hanging around it seems like.
      - myself248 3y ago
        Oh I hope nobody's doing that, rechargeables have been so good for so long. I'm just now retiring some that I bought in the 2007-2011 timeframe which have started to fail, but my 2015 purchases are still going strong with hundreds and hundreds of charge cycles on 'em. I haven't used alkalines since the 80s.
        jjeaff 3y ago
        I have not had great luck with rechargeables. They have a lower voltage than regular AA, so I find that most sensitive electronics just start out thinking the battery is already low and then stop running before the battery is fully discharged. My Z-wave keypad lock is one of those. AA batteries last about 2 months, rechargeables start giving a low battery warning after a week and hardly last 2-4.
        eternityforest 3y ago
        Have you tried lithium rechargeables with the built in converters?
        myself248 3y ago
        I return garbage products like that. Not supporting rechargeables in 1980 was sort of forgivable, but they've had 40 years to get their act together.
eternityforest 3y ago
Aside from modern barrel jack supplies, none of it is actually powers of two, it's like, 13.8v lead acid or a little higher for lithium. I think we just stay close to the numbers we do, because we just really like multiples of 12 and numbers with lots of divisors. 24 hours in a day, 360 degrees, etc. Most numbers people really like a lot seem to be on the 7-smooth numbers(https://oeis.org/A002473 https://oeis.org/A002473) list and related/overlapping sets like highly composite numbers. Which I think is super cool, because it means you can choose one and there's a good chance someone else chose it too for something similar, unless they were using renard numbers or something instead.
nippoo 3y ago
A lot of 48V infrastructure comes from the marine world - where 4 x 12V lead-acid batteries in series is common for this reason. So a lot of components already exist and can be made to work in the automotive sector with simple modifications. (In the marine world, it's much simpler to combine and split batteries in powers of 2 for cell balancing - you can take 4 x 12V batteries and charge them in parallel, discharge them in series)