50 volt - higher-voltage electrical systems

[BBQ]

.

Which van platform will have this first?

Probably the new Sprinter?

https://www.youtube.com/watch?v=LvYQ9IfB7Yg

[gerrym51]

Originally Posted by BBQ

who woulda thunk it?

it's not so exotic. it's like the change from lead acid to agm. takes a while then everyone has it

[gerrym51]

i googled 48 volt electrical systems-

dozens of articles who knew

sample one



https://www.extremetech.com/extreme/...trical-systems

[jon]

Ram will. They already have on the 2019 pickup.

https://www.greencarreports.com/news...r-fuel-economy
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[Boxster1971]

Just looked closely at the Volta online data sheets for their DC-DC converters and inverter/chargers. They are made by Magnum - good stuff.


- - Mike
2012 Sprinter 3500 Extended converted B-Van by Airstream

[mlts22]

Higher voltages are common with off-grid solar installs. It allows for skinnier wires, but the downside is potential shock if the system is poorly designed.

[Technomadness]

Shock is about the only downside I’m aware of. Higher voltage is more efficient.

12V is a legacy of ancient tech.


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[booster]

We have heard from several places over the years that 50v on DC relays and switches can cause accelerated wear and pitting, so the devices need to be somewhat different and pass lots of life testing, I think. I know that the contactors of similar voltage in forklifts and such take a real beating over time, and they are huge, and noisy.

Tesla has a 12v battery to run some stuff, I wonder how much of the stuff like this is actually at higher voltage, or did they stick to 12v for reliability?

[cruising7388]

Originally Posted by booster

We have heard from several places over the years that 50v on DC relays and switches can cause accelerated wear and pitting, so the devices need to be somewhat different and pass lots of life testing, I think.

I think the pitting is less a function of voltage than it is on the level of the heavier loads that 50 volt circuits permit when the relay is de-energized. I don't think that pitting occurs when relays make, regardless of the voltage or load. Rather, it seems to occur when the contacts start to break and there is a momentary arc between the contacts as they separate. It's a common symptom in RV transfer switch relays and separators caused by the failure to shed loads before engaging and disengaging relays.

Arcing and pitting can be mitigated with improved contact material, arcing suppression networks and providing contact wiping to slough off detritus but faced with releasing heavy loads, IMO, it's not a matter of if but when the contacts will pit and eventually fail.

[cruising7388]

Originally Posted by mlts22

Higher voltages are common with off-grid solar installs. It allows for skinnier wires, but the downside is potential shock if the system is poorly designed.

50 volts may produce some discomfort but unless someone is equipped with a pacemaker I don't think it can cause cardiac consequences. IIRC, remote audio lines in sound systems operate at 70 volts which I believe is the upper limit permitted before being subject to code protection requirements.

[booster]

50 volts is the cutoff we had to use for extra safety gear like gloves, face shields, etc in industrial plants. That was mainly for arc flash prevention. 50v will jolt you, but never saw anyone hurt unless a wrench went across it and it got hot and burned them.

Relays and switches will often have different make and break current ratings do to the difference in arcing. 50v will arc further, so will arc longer, and thus dissipate higher energy than lower voltages, and energy is what eats away or welds contacts.

[cruising7388]

Originally Posted by booster

Relays and switches will often have different make and break current ratings do to the difference in arcing. 50v will arc further, so will arc longer, and thus dissipate higher energy than lower voltages, and energy is what eats away or welds contacts.

No question that that 50 volts can potentially arc further and longer than 12 volts but I think that the actual level of arcing is also a function of the load on both contacts. If the relay isn't passing any load, I don't think relaxing the relay will produce contact arcing of any significance.

[booster]

Originally Posted by cruising7388

No question that that 50 volts can potentially arc further and longer than 12 volts but I think that the actual level of arcing is also a function of the load on both contacts. If the relay isn't passing any load, I don't think relaxing the relay will produce contact arcing of any significance.

Obviously if no current of voltage potential are present you won't get any arc, but doesn't that kind of define what switches and relays do? You will have to have every light switch, door contact, whatever be able to handle switching under power unless you do a low voltage switch and solid state relays for everything. That said, a lot of the stuff on vehicles are already doing that kind of switching on a lot of places, with control in the PCM or BCM.

[avanti]

Originally Posted by cruising7388

I think the pitting is less a function of voltage than it is on the level of the heavier loads that 50 volt circuits permit when the relay is de-energized.

The pitting is caused by arcing, which happens when a voltage exceeds the breakdown voltage of air. It really has little to do with load. That is why you can get a long spark touching a doorknob in the winter--lots of volts but negligible current. If the voltage is low, it doesn't matter how much current there is--unless you exceed the breakdown voltage, there will be no arc.

Traditionally, switches and relays meant to switch high current DC have spring-loaded contacts, which increase the velocity of the contacts, and so reduce the amount of time that arcing can occur. Such switches are a lot more expensive than what is typically used in a car. This had a lot to do with why the old "42V revolution" of the 1990's never happened.

I suspect that these days, solid-state relays will be the weapon of choice for addressing the issue. They are needed anyway for multiplexed switching systems.

[Davydd]

Has anyone investigated the Volta 48V system used by Advanced RV, Winnebago, and Prevost so far in how they solve it for safety in only Volta saying "Seven Layers including material, electronic, structural systemic safeguards." I'm assuming the chassis stays 12V and the coach equipment stays 120V or 12V as far as the user is concerned. The FitRV video really doesn't say much about the Volta system other than showing it in a concealed compartment, no touch it, and don't get it wet.

[avanti]

As I understand it, automotive engineering guidelines require extra insulation (and orange-colored sheaths) for anything 60VDC or 30VAC or greater. I think 48VDC was chosen to be comfortably below that threshold. Apparently, such a voltage is not considered to be in 'really dangerous' territory.

[BBQ]

.

It would be insane to think that anyone would want to use 50vdc for everyday switchable appliances. The switch and its copper plate will be the size of a coffee mug.

The Volta's 50v section is for charging only. Consumers do not get to come in contact with it.


I would love to see some 50vdc sparks if anyone has them; they are exciting to hear and watch.

[mlts22]

I don't know how relevant this is, but one idea I had several years back with the Transit build was to go with 24 volt batteries. This would allow me to use a buck DC-DC converter for 12 volt uses, but the inverter, solar charger, alternator, and converter could all be a higher voltage. The biggest advantage of this is being able to carry more amps on the same thickness of wires, or carrying the same amperage on skinnier wires. Since it was limited to just a few components, the risk of getting a shock was relatively low.

If done right, there isn't anything wrong with higher voltage components. The biggest downside is having to get beefier switches to handle the higher amps of DC connection and disconnection, as mentioned above.

[BBQ]

Originally Posted by mlts22

I don't know how relevant this is, but one idea I had several years back with the Transit build was to go with 24 volt batteries. This would allow me to use a buck DC-DC converter for 12 volt uses, but the inverter, solar charger, alternator, and converter could all be a higher voltage. The biggest advantage of this is being able to carry more amps on the same thickness of wires, or carrying the same amperage on skinnier wires. Since it was limited to just a few components, the risk of getting a shock was relatively low.

If done right, there isn't anything wrong with higher voltage components. The biggest downside is having to get beefier switches to handle the higher amps of DC connection and disconnection, as mentioned above.

RT tried that with their early etrek.

You will need an equalizer-charger to balance the batteries.
Otherwise they will go out of wack and meet a premature demise.

[avanti]

Originally Posted by BBQ

RT tried that with their early etrek.

You will need an equalizer-charger to balance the batteries.
Otherwise they will go out of wack and meet a premature demise.

IIRC, that was an attempt to tap into the 24V series setup to extract the 12VDC, wasn't it? If you used a DC-DC converter to convert 24VDC to 12VDC, I don't see where it would be any worse than any other series-wired battery.