48V or more?

[mcarthur]

With regards to high voltage boat systems, like batteries and motors for propulsion, 48V is often quoted as being a good mid-point for a whole variety reasons (which are not part of my question ).
One of those reasons is that a higher voltage creates issues in rules and regulations in some places, with Europe being mentioned.

Does anyone have any references where greater than 48V is a problem for being in a jurisdiction?

(please ignore whether 48V is better or worse, slower or faster, fatter or thinner , or anything other than whether going with more than 48V creates problems in countries)

[Adelie]

There was a period 25yr ago where auto companies in the US and Europe were actively moving towards 42v service in vehicles. Consideration had been given to using 48v but under extreme conditions 60v could be seen during charging. It appears that 60v is a specific red line for shock hazard. I suspect it is slightly arbitrary but not that arbitrary.

Quoting from wikipedia:
"The limiting factor for direct voltages is a shock-hazard protection limit of 60 V, which must not be exceeded even during voltage fluctuations caused by extreme conditions. This limit eliminates the option of an automotive electrical system with a nominal battery voltage of 48 V, because at low temperatures the charging voltage of the battery can attain 60 V. Also, the price, weight and volume of batteries are influenced by the number of cells, which must therefore be kept to a minimum."
https://en.wikipedia.org/wiki/42-vol...ice_of_voltage

Popular mechanics cited problems with switch longevity using higher voltages.
https://www.popularmechanics.com/cars/a2198/4226979/

You are asking about specific jurisdictions restricting the voltage. I suspect that jurisdictions may restrict voltage for mass produced items or require various safety items. If you produced a DIY system for your own use I suspect most jurisdictions wouldn't care.

I have no idea where the 60v limit came from.

[Adelie]

Here is some research into the 60v limit:

https://www.quora.com/What-is-the-sa...umans-to-touch


Here's an OSHA letter regarding required protections for anything over 50v.
https://www.osha.gov/laws-regs/stand...ons/2015-09-04

I keep reading about the phone company using 50-55v. Apparently doing so minimized necessary wire size while not incurring additional protections requirements. I keep seeing discussion of this but didn't find a primary source like OSHA.

The following telecom paper indicates a 60v limit coming out of US and Canadian safety regulations, see pg. 7.
https://www.itu.int/rec/dologin_pub....F-E&type=items

There is discussion in the paper of exceeding the 60v limit if the current is limited.



My take is that the 60vdc limit probably has force of law in Europe too for the reasons it does in the US. That's why lots of available off the shelf systems top out at 48v, the chargers only exceed 60v under extreme circumstances.

[cj88]

Just wondering who would check your DC voltage and why? Marinas only seem to care about your AC system when plugging into their supply. I suppose insurance companies might have issues when making a claim if it was the cause of the claim depending upon their policies and what you have declared.

As an aside in Australia and New Zealand the term 'hazardous potential' refers to any differential voltage that exceeds the levels defined as 'extra low voltage (ELV)' in AS/NZS3000:2010 ,clause 1.5.7(a) i.e. exceeding 50VAC or 120 V ripple-free DC.

[cal40john]

Adelie what made you think of your sign off?

I looked at that window for years and never wondered about the Latin caption.

https://www.deseretnews.com/article/...CT-DID-IT.html

[Moo]

The reason that the regulation changes at that point in most of the world is because 50Vdc is considered very low voltage.



One important reason is that it is because below that voltage threshold it is insufficient to breakdown human skin resistance and cause electrocution. Knowing this it is easy to see why almost anybody can safely work on VLV systems. This does not mean that they are not dangerous of course, they can still cause fire or explosion and such but they will not electrocute you. There are bunch of other reasons too such as the fact that a DC arc is not self quenching whereas an AC one is (the current passes through zero twice in each cycle, and reverses direction).



So in short yes it is true that you run into a lot more rules and regs both in terms of the qualifications of the installer, surveyor and in compliance.

[Adelie]

Originally Posted by cal40john

Adelie what made you think of your sign off?

I looked at that window for years and never wondered about the Latin caption.

https://www.deseretnews.com/article/...CT-DID-IT.html

When I was a kid living overseas we occasionally got random English language material which I treasured. I voraciously read a 20+yr old edition of the World Book Encyclopedia for instance even though it was missing several letters. Over time we came into possession of several issues of Mad which I enjoyed above and beyond it just being something to read in English.

When I was at the UW I encountered the window several times but didn't notice the Latin inscription until it got a writeup in the Daily, somewhere about 1990.

About a year ago I realized that I had only used 2 signature lines and the quip about boats and houses might be getting a little stale. With my penchant for being obscure (please note my location) this quote came to mind and I added it.

[a64pilot]

For whatever it’s worth hybrid autos and I’d assume the electrics operate with 300+ volts

[transmitterdan]

The EU low voltage directive (Directive 2014/35/EU) regulates voltages from 75 to 1500 VDC. But 75V is not a world standard. Some countries use 72V. Some use 63V. Some use 50V to determine when higher levels of personnel protection kick in.

All of these are a bit arbitrary. I think the EU limit of 75 is the “best”.